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1306 tools available · Every tool is filed under a category, and every category page lists all of them.
Mathematics
Percentages, fractions, powers, geometry, statistics and everyday maths, each one showing the steps behind the result.
- MathematicsPercentage CalculatorThe three questions people actually ask about percentages, answered at once, including the reverse ones.
- MathematicsPercentage Change CalculatorFind the percentage increase or decrease between two values, with the absolute difference.
- MathematicsRectangle Area CalculatorArea, perimeter and diagonal of a rectangle or square.
- MathematicsScientific CalculatorType a whole expression and get the answer, with brackets, powers, roots, logs and trigonometry.
- MathematicsCircle Area CalculatorArea, circumference and diameter of a circle from its radius.
- MathematicsWhat Percentage Is X of YTurn a part and a total into a percentage share.
- MathematicsRule of Three CalculatorSolve a direct proportion: if A gives B, what does C give?
- MathematicsEquation SolverFinds the real solutions of an equation in x, including ones no formula can give you.
- MathematicsRandom Number GeneratorDraws random whole numbers in a range, with or without repeats, from a seed you can publish.
- MathematicsDerivative Calculator with StepsThe exact derivative of a function, term by term, naming the rule used at each step.
- MathematicsPythagorean Theorem CalculatorFind the hypotenuse of a right triangle from the two shorter sides.
- MathematicsIntegral Calculator with StepsThe antiderivative where the form is one that can be recognised, and the definite integral either way.
- MathematicsTriangle Area CalculatorArea of any triangle from its base and perpendicular height.
- MathematicsCylinder Volume CalculatorVolume in cubic metres and litres, plus total surface area, of a cylinder.
- MathematicsMatrix CalculatorAdd, subtract, multiply, transpose or scale matrices of any size up to twelve by twelve.
- MathematicsCurve Fitting CalculatorThe best straight line, polynomial, exponential, power or logarithmic fit to your data, by least squares.
- MathematicsFraction CalculatorAdd, subtract, multiply or divide two fractions, with the answer simplified and as a decimal.
- MathematicsRatio Calculator (simplify and share)Simplify a ratio to its smallest whole numbers and split an amount between two parts.
- MathematicsLimit CalculatorWhere a function is heading, approached from both sides, with l'Hôpital's rule applied when the form is indeterminate.
- MathematicsTriangle SolverEvery side, every angle, the area and the two radii of any triangle, from whichever three measurements you have.
- MathematicsBox Volume CalculatorVolume in cubic metres and litres, plus surface area, of a rectangular box.
- MathematicsMatrix Inverse CalculatorThe inverse of a square matrix by Gauss-Jordan elimination, with the identity check that proves it.
- MathematicsRounding CalculatorThe same number by five different rounding rules, plus significant figures and the nearest multiple.
- MathematicsDecimal to Fraction CalculatorA decimal written as a fraction in lowest terms, including recurring decimals done exactly.
- MathematicsPercentage Difference CalculatorThe symmetric percentage difference between two values, plus the change in each direction.
- MathematicsQuadratic Formula Calculator with StepsThe roots of ax² + bx + c = 0 with the discriminant worked out, the factored form and the vertex.
- MathematicsTaylor Series CalculatorThe Taylor or Maclaurin polynomial of a function, with each coefficient and how far the approximation is off.
- MathematicsFraction to Decimal ConverterTurn any fraction into a decimal number and a percentage.
- MathematicsInterpolation CalculatorA value between the points you measured, by straight line and by the polynomial through all of them.
- MathematicsComplex Number Polar Form CalculatorA complex number in both forms, with its modulus, argument, conjugate, powers by De Moivre and all its n-th roots.
- MathematicsNewton-Raphson CalculatorA root of any function by Newton's method, with the full iteration table and an honest verdict on convergence.
- MathematicsCubic Equation CalculatorThe real roots of ax³ + bx² + cx + d = 0, by Cardano or the trigonometric form, with each root checked.
- MathematicsDifferential Equation CalculatorThe exact solution of a first-order linear equation with constant coefficients, with its equilibrium and time constant.
- MathematicsExponent CalculatorRaise any number to any power, including negative and fractional exponents.
- MathematicsNumerical Integration CalculatorThe area under a curve by the trapezium, midpoint and Simpson rules, with each one's error measured.
- MathematicsPrime Factorization CalculatorBreaks a number into its prime factors, with how many divisors it has and what they add up to.
- MathematicsLaplace Transform CalculatorThe transform of a function of time, term by term, using the standard table and linearity.
- MathematicsProportional Division CalculatorAn amount split between any number of shares in proportion, with the rounding handled so the total still adds up.
- MathematicsPrime Number CheckerWhether a number is prime, and the nearest prime above and below it.
- MathematicsRoot CalculatorFind the square root, the cube root or any nth root of a positive number.
- MathematicsBisection Method CalculatorA root found by repeatedly halving an interval, with every step shown and a check that the interval brackets one.
- MathematicsTrigonometry CalculatorSine, cosine and tangent of an angle given in degrees, plus the angle in radians.
- MathematicsLaw of Sines CalculatorThe missing side or angle from the sine rule, with the common ratio and the circumradius, and a warning when two triangles fit.
- MathematicsNumber Base ConverterConvert whole numbers between binary, octal, decimal and hexadecimal.
- MathematicsLaw of Cosines CalculatorThe third side from two sides and the angle between them, or any angle from the three sides, with the substitution shown.
- MathematicsSphere Volume CalculatorVolume and surface area of a sphere from its radius.
- MathematicsFibonacci CalculatorAny term of the Fibonacci sequence, the terms around it, the running total and how close the ratio has got to the golden ratio.
- MathematicsGCD and LCM CalculatorFind the greatest common divisor and the least common multiple of two whole numbers.
- MathematicsTriangle Area from Three SidesArea, perimeter and height of a triangle when you only know the three side lengths.
- MathematicsRoman Numeral ConverterWrite any number from 1 to 3999 in Roman numerals.
- MathematicsParabola CalculatorVertex, focus, directrix, latus rectum and roots of y = ax² + bx + c.
- MathematicsPercentage Error CalculatorHow far a measurement is from the true value, in percent and in absolute terms.
- MathematicsSuccessive Percentage ChangesThe real combined effect of two percentage changes applied one after the other.
- MathematicsLinear Equation SolverSolve ax + b = c for x, with the answer substituted back as a check.
- MathematicsLogarithm CalculatorLogarithm in any base, plus the natural logarithm and the base-2 logarithm.
- MathematicsPrism Volume CalculatorVolume and surface area of a prism whose base is a regular polygon — triangular, square, hexagonal or any other.
- MathematicsDistance Between Two PointsStraight-line distance, midpoint and direction angle between two coordinates.
- MathematicsTrapezoid Area CalculatorArea of a trapezoid from its two parallel sides and its height.
- MathematicsVector Dot and Cross Product CalculatorDot product, cross product and its magnitude, the angle between two vectors and their lengths.
- MathematicsComplex Number CalculatorProduct, quotient and sum of two complex numbers, with the modulus and argument of the first.
- MathematicsVolume by Water DisplacementThe volume of an irregular object from how far the water rises, and its density if you also weigh it.
- MathematicsFactorial Calculatorn factorial, the number of digits it has and the value of (n−1)!.
- MathematicsArithmetic Sequence CalculatorThe nth term and the sum of the first n terms of an arithmetic progression.
- MathematicsHyperbola CalculatorFoci, vertices, eccentricity, asymptotes and latus rectum of x²/a² − y²/b² = 1.
- MathematicsMatrix Determinant CalculatorThe determinant of a square matrix of any size up to twelve, by Gaussian elimination.
- MathematicsRegular Polygon CalculatorArea, perimeter, apothem, circumradius and interior angle of any regular polygon.
- MathematicsScientific Notation CalculatorTurn a number written as m × 10ⁿ into ordinary decimal form.
- MathematicsCircle Sector CalculatorArc length, sector area, chord and perimeter of a slice of a circle.
- MathematicsCone Volume CalculatorVolume and slant height of a cone from its radius and vertical height.
- MathematicsFrustum Volume Calculator (Bucket, Pot, Hopper)Volume of a truncated cone such as a bucket, a flower pot or a hopper, the volume up to any fill line, and its surface area, drawn to scale.
- MathematicsSlope and Line Equation CalculatorSlope, y-intercept, angle and x-intercept of the line through two points.
- MathematicsPlatonic Solids Calculator (Tetrahedron, Cube, Octahedron, Dodecahedron, Icosahedron)Volume, surface area, the three radii (corner, edge, face) and the angle between faces of any of the five regular solids, from the edge length.
- MathematicsEllipse Area and PerimeterArea, approximate perimeter and eccentricity of an ellipse from its two semi-axes.
- MathematicsGeometric Sequence CalculatorTerm n, the sum of the first n terms and the infinite sum of a geometric progression.
- MathematicsSignificant Figures RounderRound any number to a chosen number of significant figures, with the rounding error.
- MathematicsSystem of Equations CalculatorAny number of simultaneous linear equations solved by Gaussian elimination, with the answer substituted back.
- MathematicsTorus Volume CalculatorVolume, surface area and diameters of a torus from the ring radius and the tube radius.
- MathematicsAnnulus (Ring) Area CalculatorArea of a ring from the outer and inner radius, with the wall thickness.
- MathematicsPyramid Volume CalculatorVolume, base area and slant height of a rectangular-based pyramid.
- MathematicsCircular Segment Calculator (Arch from Span and Rise)Radius, arc length, central angle and area of a circular arch or curved window from the two measurements you can actually take: the span and the rise.
- MathematicsCone Flat Pattern Calculator (Sheet Metal, Paper, Lampshades)Angle and radii of the flat piece that rolls up into a cone or a truncated cone — a funnel, a hopper, a lampshade or a paper hat — drawn to scale.
- MathematicsCubic Bézier Curve Calculator (Point and Tangent at t)The point on a cubic Bézier curve at any t between 0 and 1, with the speed and direction of the tangent there, from the four control points.
- MathematicsEllipsoid Volume and Surface Area CalculatorVolume, approximate surface area and equal-volume sphere radius of an ellipsoid from its three semi-axes.
- MathematicsDistance from a Point to a Line CalculatorThe shortest distance from a point to a line through two points, the distance to the segment between them, and the exact spot where the perpendicular lands.
- MathematicsPolygon Area from Coordinates Calculator (Shoelace Formula)Area, perimeter and centroid of a flat shape with 3 to 6 corners from the X–Y coordinates of its corners, as used for plots of land and plans.
- MathematicsTournament Matches Calculator (Round-Robin, Knockout, Double Elimination)How many matches, rounds and byes a league, a knockout cup or a double-elimination bracket needs for any number of teams.
- MathematicsTriangle Centres Calculator (Centroid, Circumcentre, Incentre, Orthocentre)The four classic centres of a triangle, its area, the radii of the inscribed and circumscribed circles and whether it is acute, right or obtuse, from the coordinates of the three corners.
- MathematicsVenn Diagram Calculator (Three Sets, Inclusion–Exclusion)How many are in at least one, in none, in exactly one or exactly two of three overlapping groups, and in each separate region of the Venn diagram.
- MathematicsCartesian, Cylindrical and Spherical Coordinates ConverterConvert a point between x–y–z, cylindrical (ρ, φ, z) and spherical (r, θ, φ) coordinates — flat polar too — and see all of them at once.
- MathematicsDerangements Calculator (Secret Santa and the Hat-Check Problem)How many ways n people can each draw somebody else's name, and the chance that a random draw works first time.
- MathematicsGamma Function Calculator (Factorial of Any Number, Beta Function)Γ(x), the factorial of non-whole numbers, ln Γ(x) and the beta function B(x, y), to about 15 significant figures.
- MathematicsGolden Ratio CalculatorSplit any length in the golden ratio, or find the long side of a golden rectangle, for layouts, frames and design.
- MathematicsHelix Length Calculator (Spiral Staircase, Coil, Handrail, Cable Wrap)Length of material along a helix — a spiral stair handrail, a coiled wire, a cable wrapped round a drum or a pole — from its diameter, pitch and height or number of turns.
- MathematicsQuadratic Sequence nth Term CalculatorThe nth-term formula an² + bn + c of a quadratic sequence from its first three terms, with any term, the next term and the sum of the first n.
- MathematicsShannon Entropy Calculator (Information in Bits, Perplexity, Gini Impurity)The entropy in bits of up to six outcomes from their frequencies or probabilities, with the maximum, the efficiency, the perplexity and the Gini impurity.
- MathematicsSpherical Cap Calculator (Volume and Surface Area of a Dome)Volume, base radius, curved and total surface area of a spherical cap — a dome, a bowl, a bubble cut by a plane — from the sphere's radius and the cap's height.
- MathematicsStadium Shape and Capsule Calculator (Running Track, Obround, Pill)Area and perimeter of a rectangle with semicircular ends — a running track, a slot or an obround — and the volume and surface of the matching 3D capsule.
- MathematicsCircle Overlap Area Calculator (Area of Intersection of Two Circles)Area of the lens where two circles overlap, from their radii and the distance between centres, with the share of each circle covered.
- MathematicsClock Angle CalculatorAngle between the hour and minute hands of a clock at any time, and how long until they next overlap.
- MathematicsCyclic Quadrilateral Calculator (Brahmagupta's Formula)Area, both diagonals, the circumscribed radius and all four angles of a four-sided figure whose corners lie on one circle, from its four sides.
Statistics
Averages, spread, correlation and the tests that say whether a difference is real — each one showing the numbers it rests on.
- StatisticsAverage CalculatorPaste a list of numbers and get the mean, median, sum, count, minimum, maximum and range.
- StatisticsWeighted Average CalculatorAverage a list of values where each one carries a different weight or coefficient.
- StatisticsStandard Deviation CalculatorHow spread out a set of numbers is, with the subtraction and the squaring laid out line by line.
- StatisticsT-Test CalculatorWhether the difference between two sets of numbers is bigger than chance would produce, with the p value and the size of the difference.
- StatisticsLinear Regression CalculatorThe straight line that fits a set of points best, with the equation, how much it explains, and a prediction.
- StatisticsMargin of Error CalculatorThe proportion your sample found, the margin of error around it, and the interval that follows — with the finite population correction when it applies.
- StatisticsCorrelation CalculatorHow closely two sets of numbers move together, by Pearson and by rank, with a confidence interval around the answer.
- StatisticsProbability CalculatorThe chance of both, either, neither or exactly one of two independent events.
- StatisticsQuartile CalculatorThe median, the quartiles, the interquartile range and the values Tukey's rule flags as outliers.
- StatisticsBayes' Theorem CalculatorWhat a positive result really means, once the rarity of the thing being tested for is taken into account.
- StatisticsChi-Square CalculatorWhether counts differ from what you expected, or whether two categories are related, with the p value and the strength of the link.
- StatisticsCombinations and Permutations CalculatorHow many ways k items can be chosen from n, with and without counting the order.
- StatisticsMean, Median and Mode CalculatorThe three averages of a set of numbers, plus the range and the count.
- StatisticsANOVA CalculatorWhether three or more groups really differ, by comparing the variation between them against the variation inside them.
- StatisticsMoving Average CalculatorSmooth a bumpy series of numbers by averaging each value with the ones before it, and see where the trend is heading.
- StatisticsStatistical Power CalculatorWhether your study is big enough to find the difference you are looking for, and how many people it would take.
- StatisticsSkewness and Kurtosis CalculatorWhich way a distribution leans and how heavy its tails are, with the standard errors that say whether either is real.
- StatisticsPermutations with Repetition CalculatorHow many arrangements are possible when things can repeat, or when the set you are rearranging already contains duplicates.
- StatisticsCoefficient of Variation CalculatorSpread as a percentage of the mean, so two things measured on different scales can be compared for variability.
- StatisticsDice Probability CalculatorChance of rolling at least one chosen face, the expected total, and the odds of all dice matching.
- StatisticsStratified Sampling CalculatorHow many people to draw from each group so that the sample mirrors the population, with the rounding handled properly.
- StatisticsBirthday Problem CalculatorChance that two of a group share a value, with the number of pairs and the group size for even odds.
- StatisticsConfidence Interval CalculatorMargin of error and confidence interval for a sample mean, with the standard error and the sample size for half the margin.
- StatisticsNormal Distribution Probability CalculatorProbability below, above and within a value on a normal curve, with the z-score and the odds of exceeding it.
- StatisticsSample Size CalculatorSample size for a survey or inspection at a chosen confidence level and margin of error.
- StatisticsProbability of At Least One CalculatorChance that an event happens at least once over repeated independent tries, with the tries needed for even odds.
- StatisticsA/B Test Significance CalculatorWhether the difference in conversion rate between two versions of a page, email or ad is likely to be real or just chance, with the p-value and z statistic.
- StatisticsOdds to Probability CalculatorImplied probability from odds, in decimal and fractional form, with the return on a stake.
- StatisticsZ-Score CalculatorHow many standard deviations a value sits from the mean.
- StatisticsExpected Value CalculatorExpected value of three possible outcomes, with the variance and standard deviation of the result.
- StatisticsSensitivity and Specificity Calculator (Diagnostic Test Accuracy, PPV, NPV)Sensitivity, specificity, predictive values, accuracy and likelihood ratios from the four counts of a test result table, and the predictive values at any other prevalence.
- StatisticsPoisson Distribution CalculatorProbability of exactly k events, of none, and of at least one, when the average rate is known.
- StatisticsBinomial Probability CalculatorProbability of exactly k successes in n independent trials, with the expected value.
- StatisticsBest-of Series Probability Calculator (Playoffs: Best of 3, 5, 7)The chance that a team wins a best-of-3, 5, 7 or 9 series, and how many games it is likely to take, from its chance of winning one game.
- StatisticsCohen's d Calculator (Effect Size Between Two Groups)Cohen's d and Hedges' g from the means, standard deviations and sizes of two groups, with a 95 % interval, the common-language effect size and the usual small/medium/large label.
- StatisticsCombined Standard Deviation Calculator (Merging Two or Three Groups)The mean and standard deviation of several groups put together, from each group's size, mean and standard deviation — without needing the raw data.
- StatisticsError Propagation Calculator (Uncertainty of Sums, Products, Quotients, Powers)The uncertainty of A + B, A − B, A × B, A ÷ B and Aⁿ from the uncertainties of A and B, using the standard rules for independent errors.
- StatisticsSample Size for Comparing Two ProportionsHow many people you need in each group to detect a difference between two rates.
- StatisticsSampling Distribution of the Mean Calculator (Standard Error and Sample-Mean Probabilities)The standard error of a sample mean, the chance that a sample of size n averages above, below or this far from the true mean, and the range holding 95 % of sample means.
- StatisticsSample Size for Comparing Two MeansHow many subjects you need per group to detect a given difference between two averages.
- StatisticsAcceptance Sampling Calculator (Single Sampling Plan, OC Curve Point)Chance that a lot passes inspection for a plan of n items checked and c defects allowed, with the average outgoing quality and the average number of items inspected.
- StatisticsCohen's Kappa Calculator (Agreement Between Two Raters)Cohen's kappa, observed and chance agreement, an approximate 95 % interval and the Landis–Koch label for two raters who each said yes or no to the same items.
- StatisticsCorrelation Confidence Interval Calculator (Fisher z Transformation)A confidence interval for the true correlation behind a sample r, by Fisher's z transformation, with an approximate p-value for r = 0 and the shared variance r².
- StatisticsCoupon Collector Calculator (How Many Packs to Complete the Set)How many random draws you need on average to collect every different item in a set, or a given number of them, with the typical spread.
- StatisticsEmpirical Rule Calculator (68–95–99.7) and Chebyshev's InequalityThe range within k standard deviations of the mean, the share of data inside it if the data are normal, and the weaker share guaranteed for any shape of data.
- StatisticsExponential Distribution Calculator (Waiting Times)Chance that the next event — a customer, a failure, a call — comes within a given time when events arrive at random at a known average rate.
- StatisticsExponential Smoothing Forecast Calculator (Simple, Next-Period Demand)Next-period forecast from five periods of actual values with simple exponential smoothing, plus the average error and bias of the forecasts it would have made.
- StatisticsGambler's Ruin Calculator (Chance of Reaching Your Goal Before Going Broke)The chance of reaching a target stake before losing everything, and how long it takes, when you bet one unit at a time at fixed odds.
- StatisticsHerfindahl-Hirschman Index (HHI) Calculator (Market Concentration)Market concentration from up to six firms' market shares, the equivalent number of equal-sized firms, and how much a merger of the first two would raise the index.
- StatisticsLaspeyres, Paasche and Fisher Price Index Calculator (Cost of Living Basket)Price index of a small basket of goods from base-period and current prices and quantities, by the Laspeyres, Paasche and Fisher methods.
- StatisticsLognormal Distribution Calculator (Mean, Median, Mode, Probability)Mean, median, mode and standard deviation of a lognormal variable, the μ and σ behind it, and the chance that it stays at or below any value.
- StatisticsNegative Binomial Calculator (Trials Until the r-th Success)The chance of getting your r-th success on a given trial or within a given number of trials, and how many trials it takes on average.
- StatisticsPareto Principle Calculator (80/20 Rule, Pareto Index and Gini)Fit a Pareto distribution to a rule like 'the top 20 % hold 80 %' and read off the Pareto index, the Gini coefficient and the shares held by the top 1 %, top 10 % and bottom half.
- StatisticsRelative Risk and Odds Ratio Calculator (2×2 Table)Relative risk, odds ratio, risk difference and number needed to treat from a 2×2 table, with 95 % confidence intervals.
- StatisticsWilson Score Interval Calculator (Confidence Interval for a Proportion)A confidence interval for a percentage from successes out of trials, by the Wilson method, with the simple textbook interval alongside to show where that one goes wrong.
- StatisticsZero Events Upper Limit Calculator (Rule of Three)After n trials with no failures, accidents or side effects, how high the true rate can still be at your confidence level — and how many clean trials it takes to rule out a given rate.
- StatisticsBenford's Law Calculator (Expected First-Digit Frequencies)How often a number should start with each digit in real-world data, the expected count in your data, and a z-test of whether your own count is too far off.
- StatisticsHypergeometric Probability CalculatorOdds of drawing a given number of the right things, when you draw without putting them back.
- StatisticsTriangular Distribution Calculator (Best, Most Likely, Worst Case)Mean, standard deviation, median, the chance of staying under a value and any percentile of a triangular distribution defined by a minimum, a most likely value and a maximum.
- StatisticsTwo-State Markov Chain Calculator (Weather Model, Steady State)The chance of being in each of two states after any number of steps, and the long-run share of time in each, from the two switching probabilities.
Converters
Metric, imperial and technical units converted from a single shared library, so every factor is identical across the whole site.
- ConvertersLength ConverterConvert between metres, centimetres, inches, feet, yards, miles and nine other length units.
- ConvertersTemperature ConverterConvert between Celsius, Fahrenheit, Kelvin and Rankine, with the offset handled correctly.
- ConvertersMass & Weight ConverterConvert kilograms, grams, tonnes, pounds, ounces, stones and both US and UK tons.
- ConvertersPressure ConverterConvert bar, psi, pascal, kPa, MPa, atmospheres, mmHg, torr and metres of water column.
- ConvertersVolume ConverterConvert litres, millilitres, cubic metres, gallons, pints, cups and fluid ounces.
- ConvertersSpeed ConverterConvert km/h, mph, metres per second, feet per second and knots.
- ConvertersArea ConverterConvert square metres, square feet, hectares, acres and seven other area units.
- ConvertersPower ConverterConvert watts, kilowatts, megawatts, horsepower, metric horsepower, BTU/h and tons of refrigeration.
- ConvertersEnergy ConverterConvert joules, kilojoules, kWh, calories, kilocalories, BTU and therms.
- ConvertersFuel Economy ConverterConvert L/100 km, km/L, miles per US gallon and miles per imperial gallon.
- ConvertersTime Duration ConverterConvert seconds, minutes, hours, days, weeks, months and years as durations.
- ConvertersData Storage ConverterConvert bits, bytes, kB, MB, GB, TB and the binary KiB, MiB, GiB and TiB.
- ConvertersTorque ConverterConvert newton-metres, kilogram-force metres, pound-force feet and pound-force inches.
- ConvertersForce ConverterConvert newtons, kilonewtons, kilogram-force, pound-force, tonne-force and dynes.
- ConvertersAngle ConverterConvert degrees, radians, gradians, turns, milliradians, arcminutes and arcseconds.
- ConvertersDensity ConverterConvert kg/m³, g/cm³, kg/L, t/m³, lb/ft³ and lb/in³.
- ConvertersFlow Rate ConverterConvert m³/h, m³/s, L/s, L/min, US gallons per minute and cubic feet per minute.
- ConvertersFrequency & Rotation ConverterConvert hertz, kilohertz, megahertz, revolutions per minute and radians per second.
- ConvertersData Transfer Rate ConverterConvert Mbps, MB/s, Gbit/s and the other units used for internet and disk speed.
- ConvertersAcceleration ConverterConvert m/s², g, ft/s², gal and (km/h)/s.
- ConvertersMass Flow ConverterConvert kg/s, kg/h, t/h, t/day, g/s and pounds per hour.
- ConvertersIlluminance ConverterConvert lux, foot-candles, phot and nox.
- ConvertersDynamic Viscosity ConverterConvert pascal seconds, millipascal seconds, centipoise, poise and imperial units.
- ConvertersDecimal Degrees Converter (Degrees Minutes Seconds)Convert latitude and longitude between degrees-minutes-seconds and decimal degrees, in either direction.
- ConvertersSI Prefix ConverterConvert between metric prefixes from quetta down to quecto, including the four added in 2022.
- ConvertersPPM, PPB and Percent ConverterConvert parts per million, parts per billion, percent, per mille and milligrams per kilogram.
Electricity
Ohm's law, single and three-phase power, voltage drop, cable sizing and electronics basics.
- ElectricityOhm's Law CalculatorEnter any two of voltage, current and resistance and get the third, plus the power.
- ElectricityElectricity Cost CalculatorDaily, monthly and yearly running cost of any appliance from its wattage and hours of use.
- ElectricitySingle-Phase Power CalculatorActive, apparent and reactive power of a single-phase load from voltage, current and power factor.
- ElectricityVoltage Drop CalculatorVoltage drop in volts and percent along a copper cable, for single-phase and three-phase circuits.
- ElectricityThree-Phase Power CalculatorActive and apparent power of a balanced three-phase load, in watts, kW and kVA.
- ElectricityCable Cross-Section CalculatorMinimum conductor cross-section needed to keep voltage drop within a chosen limit.
- ElectricityMotor Full-Load Current CalculatorEstimate the full-load current of a three-phase motor from its shaft power, efficiency and power factor.
- ElectricityAWG to mm² ConverterConvert an American Wire Gauge number into conductor diameter and cross-sectional area.
- ElectricitySolar Panel Output CalculatorDaily and yearly production of a photovoltaic array, and the value of the electricity it replaces.
- ElectricitySeries and Parallel Resistor CalculatorEquivalent resistance of two resistors connected in series and in parallel.
- ElectricitykVA to Amps CalculatorCurrent drawn by a load rated in kVA, for single-phase and three-phase supplies.
- ElectricityRLC Impedance and Resonance CalculatorImpedance, phase angle, resonant frequency, Q factor and bandwidth for a series or parallel RLC circuit.
- ElectricityLED Series Resistor CalculatorResistor value and power needed to run an LED safely from a given supply.
- ElectricityBattery Life CalculatorEstimate how long a battery will last from its capacity and the current drawn.
- ElectricitySolar Battery Bank CalculatorBattery capacity in amp-hours for a daily consumption and a chosen number of cloudy days.
- ElectricityBattery Charging Time CalculatorHow long a battery takes to charge, with the charge rate expressed as a C-rate.
- ElectricityWire Resistance CalculatorResistance of a conductor from its length, cross-section and resistivity.
- ElectricityRMS CalculatorThe root mean square of a waveform or a list of readings, with peak, average, form factor and crest factor.
- ElectricityVoltage Divider CalculatorOutput voltage, current and power dissipation of a two-resistor divider.
- ElectricityInverter Size CalculatorInverter rating for a given load, with the DC current it will draw at full load and on surge.
- ElectricityGenerator Size CalculatorThe generator rating needed for a given running load plus the surge of the largest motor, in W and kVA.
- ElectricityLED Strip Power Supply CalculatorTotal wattage, current and recommended power supply size for a run of LED strip.
- ElectricityPower Factor Correction CalculatorCapacitor bank size in kvar needed to raise the power factor from one value to another.
- ElectricityRoom Lighting CalculatorTotal lumens and number of luminaires needed to reach a target illuminance.
- ElectricitySpeaker Impedance CalculatorThe load an amplifier sees from several drivers wired in series, in parallel or series-parallel, with the current and voltage.
- ElectricityAmplifier Power CalculatorHow many watts a speaker needs to reach a given loudness at a given distance, with the headroom counted in.
- ElectricityCable Power Loss CalculatorPower wasted as heat in a cable run, and what that waste costs over a year.
- ElectricityResistor Color Code Calculator (4 and 5 Bands)Resistance and tolerance range of a resistor from the colours of its bands, for 4-band and 5-band resistors.
- ElectricityInductor Combination CalculatorTotal inductance of any number of coils in series or parallel, with the other arrangement shown alongside.
- ElectricityMotor Efficiency CalculatorEfficiency, losses and the yearly cost of those losses for a motor.
- ElectricityBattery Pack Configuration CalculatorVoltage, capacity and energy of a series-parallel pack, with the runtime and current at a given load.
- ElectricitySeries and Parallel Capacitor CalculatorEquivalent capacitance of two capacitors in parallel and in series.
- ElectricityPassive Crossover CalculatorCapacitor and inductor values for a first or second order passive crossover, from the crossover frequency and the driver impedances.
- ElectricityAudio Level ConverterConvert between dBu, dBV, volts and dBFS, with the alignment level you choose, plus peak and peak-to-peak voltage.
- ElectricityLumens to Watts CalculatorLuminous efficacy of a lamp, the incandescent equivalent and the yearly running cost.
- ElectricityPV String Sizing CalculatorMaximum modules per string from the cold open-circuit voltage, with the minimum for the MPPT window.
- ElectricityInductive and Capacitive Reactance CalculatorReactance of a coil and a capacitor at a given frequency, plus the resonant frequency of the pair.
- ElectricityCable Ampacity Derating CalculatorCorrected current-carrying capacity of a cable, and the table value a design current needs.
- Electricity4–20 mA Scaling Calculator (Current Loop to Process Value)The process value a 4–20 mA signal stands for, its position in the span, the current for a given process value, the voltage across a sense resistor and what the NAMUR NE43 limits say about the reading.
- ElectricityPCB Trace Width Calculator (IPC-2221, Current and Temperature Rise)Width of a copper trace for a current and an accepted temperature rise, on an outer or inner layer, with its resistance, voltage drop and power loss.
- ElectricityLM317 Output Voltage Calculator (Resistor Values for the Adjustable Regulator)The output voltage of an LM317 from its two resistors, the R2 needed for the voltage you want, the input voltage it requires and the heat it has to dissipate.
- ElectricityAudio Headroom CalculatorHeadroom, crest factor, the noise floor of a given bit depth and how much of the available range a recording actually uses.
- ElectricityTransformer Turns Ratio CalculatorVoltage ratio and secondary turns of a transformer from the primary and secondary voltages.
- ElectricityCapacitor Energy CalculatorEnergy stored in a capacitor and the charge it holds, from capacitance and voltage.
- ElectricityRC Time Constant and Filter CalculatorTime constant, settling time and cut-off frequency of a resistor-capacitor pair.
- ElectricityThree-Phase Fault Current CalculatorProspective short-circuit current at a transformer's terminals, with the peak current and the fault level.
- ElectricityOp-Amp Gain CalculatorGain of an op-amp stage in both configurations, in ratio and decibels, with the output and the bandwidth left.
- ElectricityAntenna Length CalculatorQuarter-wave, half-wave and full-wave lengths for a frequency, with the dipole half-length.
- ElectricityADC Resolution, ENOB and Aliasing CalculatorStep size, ideal signal-to-noise ratio, effective number of bits, quantisation noise and the alias frequency of a signal sampled by an analogue-to-digital converter.
- ElectricityButterworth LC Low-Pass Filter Calculator (Coil and Capacitor Values)Capacitor and inductor values of a 2nd to 5th order Butterworth LC low-pass filter between equal source and load resistances, and its attenuation at any frequency.
- ElectricityCapacitor Code Calculator (104, 473, 222…)Capacitance in picofarads, nanofarads and microfarads from the three-digit code printed on ceramic and film capacitors.
- ElectricityCrystal Load Capacitor Calculator (Oscillator Capacitors C1, C2)The two capacitors to fit on a crystal oscillator for the crystal's specified load capacitance, the load you actually get with the parts you have, and the frequency error that difference causes.
- ElectricityI2C Pull-Up Resistor Calculator (SDA and SCL)The window of pull-up resistor values that an I2C bus allows for its supply voltage, speed mode and bus capacitance, and whether the resistor you picked sits inside it.
- ElectricitySallen-Key Low-Pass Filter Calculator (Unity-Gain, Second Order)Cut-off frequency, natural frequency, Q and passband peaking of a unity-gain Sallen-Key low-pass filter from its two resistors and two capacitors, and the C1 that makes it maximally flat.
- ElectricitySolenoid Calculator (Magnetic Field and Inductance)Magnetic field inside a coil, its inductance by the long-coil formula and by Wheeler's formula, stored energy and flux, with the coil drawn to scale.
- Electricity555 Timer Calculator (Astable and Monostable)Frequency, high and low times and duty cycle of a 555 timer in astable mode from R1, R2 and C, and the pulse length in monostable mode.
- ElectricityUART Baud Rate Calculator (Error, Divisor and Transfer Time)The divisor to load for a baud rate, the error it leaves with your clock (in normal and double-speed mode), the bits that make up a frame, the real data rate and the time to send a message.
- ElectricityVSWR and Return Loss Calculator (Antenna and Cable Mismatch)VSWR, reflection coefficient, return loss, mismatch loss and the power reflected back, from the line impedance and the load you actually have.
- ElectricityJunction Temperature and Heatsink CalculatorTemperature of a semiconductor's junction, case and heatsink from the power it dissipates and the chain of thermal resistances, plus the largest heatsink resistance you can get away with.
- ElectricityCable Short-Circuit Withstand CalculatorMinimum cable cross-section for a fault current and clearing time, and how long a given cable survives it.
- ElectricitySolar Panel Payback CalculatorSee how long a solar system takes to pay for itself, with your own tariffs and panel degradation.
- ElectricityStar-Delta (Y-Δ) Conversion CalculatorEquivalent star resistances from three delta resistances, and back again.
- ElectricityWheatstone Bridge CalculatorBridge output voltage, the resistance that would balance it, and the sensitivity in millivolts per ohm.
- ElectricityCurrent Divider CalculatorHow a current splits between two or three resistors in parallel, with the equivalent resistance and the voltage across them.
- ElectricityMicrostrip Impedance Calculator (PCB Trace)Characteristic impedance and propagation delay of a PCB trace over a ground plane, by the IPC-2141 formula, with a check of its range of validity.
- ElectricityBrushless Motor Kv and Torque Constant Calculator (BLDC, Drone Motors)The torque constant, no-load speed, speed and torque under load, shaft power and efficiency of a brushless motor from its Kv rating, voltage, current, no-load current and winding resistance.
- ElectricityBoost Converter Calculator (Duty Cycle and Inductor)Duty cycle, inductor value, ripple and peak current, and input current of a step-up (boost) converter from the voltages, load current, switching frequency and efficiency.
- ElectricityBuck Converter Calculator (Duty Cycle and Inductor)Duty cycle, inductor value, ripple and peak current, and input current of a step-down (buck) converter from the voltages, load current, switching frequency and efficiency.
- ElectricityCoaxial Cable Impedance CalculatorCharacteristic impedance, capacitance and inductance per metre, velocity factor and delay of a coaxial line, with its cross-section drawn to scale.
- ElectricitydBm to Watts ConverterConvert a power in dBm to milliwatts, watts and dBW, with the RMS voltage it produces across a 50 Ω load.
- ElectricityEIRP, ERP and Field Strength Calculator (Antenna Power and Exposure Distance)Effective radiated power from the transmitter power, cable loss and antenna gain, the field strength and power density at a distance, and how far away a power-density limit is met.
- ElectricityL-Network Impedance Matching Calculator (Antenna Tuner, RF Match)Coil and capacitor values of an L-network that matches one resistance to another at a chosen frequency, in both the low-pass and the high-pass version.
- ElectricityMotor Synchronous Speed and Slip CalculatorSynchronous speed of an AC motor from the supply frequency and number of poles, and the slip of an induction motor from its nameplate speed.
- ElectricityNoise Figure Cascade Calculator (Friis Formula)Total noise figure, noise temperature and gain of a receive chain of up to three stages (low-noise amplifier, cable, mixer, amplifier), and how much of the noise comes from the stages after the first.
- ElectricityPi and T Attenuator Calculator (Resistive Pad Values)The resistor values of a matched T or pi attenuator for a given attenuation and impedance, and the power the pad has to dissipate.
- ElectricityPower Supply Hold-Up Capacitor Calculator (Bulk Capacitor Sizing)The bulk capacitance a power supply needs to ride through a given hold-up time, the energy that involves, and the hold-up time a capacitor you already have would give.
- ElectricityOscilloscope Bandwidth and Rise Time CalculatorThe rise time an oscilloscope and probe will show for a given signal, the error that adds, the bandwidth the signal really contains and the system bandwidth needed to measure it within a chosen error.
- ElectricitySkin Depth Calculator (Skin Effect)How deep alternating current really flows in a conductor at a given frequency, the largest strand worth using, and an estimate of the extra AC resistance.
- ElectricityStrain Gauge Bridge Calculator (Wheatstone Output, Quarter, Half, Full)The output of a strain gauge Wheatstone bridge for a given strain, gauge factor and excitation, for quarter, half and full bridges, with the resistance change and the non-linearity of the quarter bridge.
- ElectricityThermal Noise and Receiver Sensitivity Calculator (kTB)The thermal noise floor of a receiver for its bandwidth and temperature, the weakest signal it can decode from its noise figure and the SNR it needs, and the noise voltage across a resistor.
- ElectricityTotal Harmonic Distortion (THD) Calculator for Voltage and CurrentTHD from the fundamental and up to six harmonics, the same distortion against the total RMS value (THD-R), the total RMS and the largest single harmonic.
- ElectricityThree-Phase Voltage Unbalance Calculator (NEMA and IEC)Percentage voltage unbalance of a three-phase supply from the three line voltages, by the NEMA definition and by the IEC negative-sequence definition, with what it means for a motor.
- ElectricityUPS and Battery Backup Runtime CalculatorWork out how long a battery bank will carry a given load through a power cut.
- ElectricityAC Generator EMF Calculator (Faraday's Law)Peak, RMS and instantaneous voltage of a coil spinning in a magnetic field, with the sine wave drawn over two turns.
- ElectricityCapacitor Discharge Time CalculatorHow long a capacitor takes to discharge through a resistor to a safe voltage, the voltage left after any time, and the energy it held.
- ElectricityConduit Fill Calculator (Cables in a Conduit or Trunking)How full a conduit is with a given number of same-size cables, the fill the code allows for that number of cables, and the most cables that fit.
- ElectricityDish Antenna Gain Calculator (Parabolic Reflector, dBi)Gain in dBi, beamwidth and effective aperture of a parabolic dish from its diameter, the frequency and the aperture efficiency.
- ElectricityGround Rod Resistance Calculator (Earth Electrode, Dwight)Resistance to earth of a single vertical ground rod from the soil resistivity, rod length and diameter, and the voltage it rises to for a given current.
- ElectricityMaximum Power Transfer Calculator (Load Matching)Power, voltage, current and efficiency in a load fed from a source with internal resistance, and how close that load comes to the most the source could ever deliver.
- ElectricityNichrome Wire Calculator (Heating Element Length)Length of nichrome wire for a heating element of a given voltage and power, with the resistance, the current and the power per area of wire surface.
- ElectricityNTC Thermistor Calculator (Beta Equation)Temperature from the resistance of an NTC thermistor, and its resistance at any temperature, using the B (beta) value from the datasheet.
- ElectricityOp-Amp Slew Rate and Full-Power Bandwidth CalculatorThe highest frequency an op-amp can reproduce at a given output amplitude, the slew rate your signal needs, and the largest undistorted swing at your frequency.
- ElectricityParallel Plate Capacitor Calculator (Capacitance from Area, Gap and Dielectric)Capacitance, charge, stored energy and electric field of two parallel plates from their area, the gap, the insulator between them and the voltage.
- ElectricityRC Filter Frequency Response CalculatorGain in dB, output-to-input ratio and phase shift of a first-order RC low-pass or high-pass filter at any frequency, with its response curve drawn.
- ElectricityRectifier Ripple Calculator (Smoothing Capacitor)Peak-to-peak ripple voltage on the smoothing capacitor of a half-wave or full-wave rectifier, and the capacitance needed for a ripple you can accept.
- ElectricityRL Circuit Calculator (Inductor Current and Time Constant)Current in a coil a given time after a voltage is switched on, the final current, the time constant L ÷ R and the energy stored in the magnetic field.
- ElectricitySolar Panel Temperature Calculator (NOCT and Power Loss)Cell temperature of a solar panel from the air temperature and sunlight, using its NOCT, and the power the panel delivers after the heat loss.
- ElectricityThree-Phase Neutral Current Calculator (Unbalanced Loads)The current that flows in the neutral of a three-phase four-wire supply when the three phase currents are unequal, with the unbalance and the neutral as a share of the largest phase.
- ElectricityTransistor Base Resistor Calculator (Switching)Base resistor that drives a bipolar transistor fully on as a switch, from the drive voltage, the load current and the transistor's gain.
- ElectricityRectangular Waveguide Cut-Off Frequency Calculator (WR-90, TE10)Cut-off frequency of the TE10, TE20, TE01 and TE11 modes of a rectangular waveguide, with the guide wavelength and group velocity at your operating frequency.
- ElectricityZener Diode Resistor CalculatorSeries resistor for a zener voltage regulator, the power the resistor and the zener must handle, from the supply, zener voltage and load current.
- ElectricityBattery Internal Resistance CalculatorInternal resistance of a battery or cell from its voltage with and without a load, with the heat it loses and the current it could deliver into a short.
- ElectricityIlluminance from a Lamp Calculator (Inverse Square and Cosine Law)Light level in lux at any point on a floor, desk or wall below a lamp, from its luminous intensity, height and how far to the side the point is.
- ElectricityLinear Regulator Heat and Heatsink CalculatorHow much heat a linear voltage regulator such as a 7805 or LM317 produces, how hot it gets without a heatsink, and the heatsink rating it needs.
- ElectricityPeukert's Law Battery Runtime CalculatorHow long a battery really lasts at a given current, allowing for the capacity it loses when discharged faster than its rated time.
- ElectricityPT100 / PT1000 RTD Calculator (IEC 60751)Resistance of a platinum PT100 or PT1000 sensor at any temperature, and the temperature that a measured resistance means, using the IEC 60751 equation.
Mechanics
Force, torque, rotation, gear ratios, belt speed, stress and the mechanical calculations used on the shop floor.
- MechanicsTorque CalculatorTorque from a force applied at a distance, in N·m, kgf·m and lbf·ft.
- MechanicsForce Calculator (F = m·a)Force from mass and acceleration, plus the weight of that mass under standard gravity.
- MechanicsMechanical Power from Torque and SpeedShaft power in watts, kW and horsepower from torque and rotational speed.
- MechanicsGear Ratio CalculatorGear ratio, output speed and output torque from the number of teeth on each gear.
- MechanicsStress CalculatorDirect stress from a force acting on a cross-section, in MPa, psi and kgf/cm².
- MechanicsCutting Speed and RPM CalculatorConvert between surface cutting speed and spindle speed for a given tool or workpiece diameter.
- MechanicsPulley Speed CalculatorDriven pulley speed, drive ratio and belt linear speed from two pulley diameters.
- MechanicsBolt Tightening Torque CalculatorTightening torque needed to reach a target bolt preload, using the nut-factor method.
- MechanicsMaterial Weight CalculatorWeight of a rectangular bar or plate, with weight per metre and per square metre.
- MechanicsHydraulic Cylinder Force CalculatorPush and pull force of a hydraulic cylinder from bore, rod diameter and working pressure.
- MechanicsTapping Drill Size CalculatorDrill diameter for a metric thread at a chosen engagement, plus the clearance and pitch diameters.
- MechanicsBeam Deflection CalculatorSag of a simply supported beam with a central point load, and the span-to-deflection ratio.
- MechanicsBelt Length CalculatorApproximate belt length and wrap angle on the small pulley from two diameters and centre distance.
- MechanicsElastic Elongation CalculatorHow much a bar stretches under load, with the resulting strain and stress.
- MechanicsMachining Feed Rate CalculatorTable feed in mm/min from spindle speed, feed per tooth and number of teeth.
- MechanicsLever CalculatorOutput force and mechanical advantage of a lever from the two arm lengths.
- MechanicsBearing Life (L10) CalculatorBasic rating life of a rolling bearing in hours, revolutions and years of continuous running.
- MechanicsSling Angle Load CalculatorTension in each sling leg at a given angle from vertical, with the angle factor and the sideways pull.
- MechanicsSpring Rate CalculatorSpring stiffness in N/m and N/mm from a known force and deflection, with the stored energy.
- MechanicsShaft Torsion Stress CalculatorShear stress and section modulus of a solid round shaft under torque.
- MechanicsEuler Buckling Load CalculatorCritical buckling load of a column, with the stress at that load and the slenderness ratio.
- MechanicsGear Module and Centre Distance CalculatorPitch diameter, outside diameter, circular pitch and the centre distance of a gear pair.
- MechanicsPump and Fan Affinity Laws CalculatorFlow, head and power at a new speed, with the power saved and what that saves in a year.
- MechanicsSecond Moment of Area CalculatorI and W for a solid rectangular section and a solid round section.
- MechanicsCentrifugal Force CalculatorForce on a rotating mass, in newtons, kilogram-force and g.
- MechanicsHelical Compression Spring CalculatorSpring rate, deflection under load, spring index, Wahl factor and the corrected shear stress.
- MechanicsHydraulic Pump Flow CalculatorFlow delivered by a pump and the drive power it needs at a working pressure.
- MechanicsStepper Motor Steps per mm Calculator (3D Printers and CNC)Steps per millimetre for a belt or lead-screw axis, the distance per step and the top speed your controller's step rate allows.
- MechanicsSheet Metal Bend Allowance CalculatorBend allowance and total flat length for a sheet metal part before folding.
- MechanicsFillet Weld Size CalculatorThroat and leg size a fillet weld needs for a load, and the capacity of a weld you already have.
- MechanicsNPSH Available CalculatorNet positive suction head available at a pump, the margin over what it requires, and the highest suction lift it allows.
- MechanicsTolerance Stack-Up Calculator (Worst Case and RSS)Nominal gap and the smallest and largest gap of an assembly of up to five parts, by worst-case arithmetic and by the statistical root-sum-square method.
- MechanicsHydraulic Motor Torque CalculatorTorque, shaft speed and power of a hydraulic motor from pressure, displacement and flow.
- MechanicsPlanetary Gear Ratio CalculatorThe three ratios an epicyclic set can give depending on which member is held, and the planet tooth count.
- MechanicsBeam Natural Frequency CalculatorFirst and second natural frequencies of a simply supported beam, with the static deflection and the deflection-based estimate.
- MechanicsFlywheel Energy CalculatorStored energy, moment of inertia and rim speed of a solid disc flywheel.
- MechanicsLead Screw Torque CalculatorTorque to raise and to lower a load on a power screw, with the efficiency and the drive power.
- MechanicsOrifice Plate Flow CalculatorFlow rate through an orifice plate from the differential pressure, with the beta ratio and velocities.
- MechanicsFatigue Life Calculator (Basquin)Cycles and running hours to fatigue failure at a stress amplitude, with the stress giving a million cycles.
- MechanicsMachining Time CalculatorCutting time for a turning pass, with spindle speed, feed rate in mm/min and material removal rate.
- MechanicsMean Piston Speed CalculatorAverage piston speed at a given engine speed, and the rpm that reaches 20 m/s.
- MechanicsBolt Circle (PCD) CalculatorDistance between neighbouring holes and the X–Y coordinates of the holes on a pitch circle — flanges, wheel hubs, rotary tables — drawn to scale.
- MechanicsCapstan Equation Calculator (Rope Friction Round a Post)How much load a small hold force can restrain when a rope is wrapped round a post, bollard or drum, how much force a given load needs, and how many turns it takes.
- MechanicsMetric Thread Dimensions Calculator (M10×1.5, Tensile Stress Area)Pitch diameter, minor diameters, thread depth and tensile stress area of any ISO metric thread, plus the axial load at a stress you choose.
- MechanicsMilling Material Removal Rate and Spindle Power CalculatorCubic centimetres of metal removed per minute by a milling cut, the power at the cutting edge, and the power the spindle motor needs, from the cut sizes, the feed and the specific cutting force.
- MechanicsPump Power CalculatorShaft power a pump needs for a given flow, head and efficiency.
- MechanicsShaft Diameter from Power and Speed Calculator (Torsion, Solid and Hollow)The smallest solid shaft that carries a given power at a given speed without exceeding the allowable shear stress, and the hollow shaft that does the same job lighter.
- MechanicsSlider-Crank Calculator (Piston Position, Velocity and Acceleration)Piston travel, velocity and acceleration at any crank angle of an engine, compressor or pump, with mean piston speed and the peak acceleration at top dead centre.
- MechanicsTaper Calculator (Angle, Ratio, Taper per Foot, Tailstock Offset)Half angle for the compound slide, included angle, 1 : n ratio, taper per foot and tailstock offset for a taper turned between a large and a small diameter.
- MechanicsVibration Isolation Transmissibility Calculator (Machine on Rubber Mounts)Natural frequency, static deflection and the share of the vibration force that reaches the floor for a machine on springs or rubber mounts, with the transmissibility curve against speed.
- MechanicsWorm Gear Efficiency and Self-Locking CalculatorEfficiency, reverse efficiency, self-locking, output torque and speed, centre distance and heat loss of a worm and wheel from the starts, teeth, module, worm diameter and friction.
- MechanicsBall-End Mill Scallop (Cusp) Height CalculatorHeight of the ridges a ball-nose cutter leaves between passes on a 3D surface, and the largest stepover that keeps them under the finish you want.
- MechanicsRoller Chain Length Calculator (Number of Links)Number of links for a roller chain between two sprockets from the teeth, the centre distance and the pitch, rounded up to an even number, with the centre distance you really get.
- MechanicsRadial Chip Thinning Calculator (Feed Compensation for Light Radial Cuts)The real chip thickness when the radial depth of cut is less than half the cutter diameter, and the higher feed per tooth to program so the tooth still cuts the chip you intended.
- MechanicsConveyor Belt Capacity Calculator (Tonnes per Hour)Tonnes per hour carried by a belt conveyor from the belt speed, the cross-section of material on the belt and its bulk density, with the load on each metre of belt.
- MechanicsDamped Oscillator Calculator (Mass–Spring–Damper)Damping ratio, natural and damped frequency and the position at any moment of a mass on a spring with a damper, with the motion drawn over time.
- MechanicsDisc Clutch Torque Capacity Calculator (Uniform Wear and Uniform Pressure)The torque a plate clutch or disc brake can transmit from its friction coefficient, clamping force and lining diameters, for a worn-in and a new lining, with the power and pressures involved.
- MechanicsPascal Press Calculator (Hydraulic Jack Force Multiplication)Force on the large piston of a hydraulic press or jack from the force on the small piston and the two piston diameters, with the fluid pressure and the stroke.
- MechanicsPress Fit (Interference Fit) CalculatorContact pressure, pressing force, slipping torque and hub stress for a shaft pressed into a hub with a given diametral interference — Lamé thick-cylinder theory.
- MechanicsRotor Balance Grade Calculator (ISO 1940 / ISO 21940: Permissible Unbalance)The residual unbalance a rotor may keep for a chosen balance quality grade G, at its operating speed and mass — in g·mm, per plane, as an eccentricity, and as the force on the bearings.
- MechanicsSine Bar Calculator (Gauge Block Stack for an Angle)The gauge block stack that tilts a sine bar to a wanted angle, the angle a given stack produces, and how much a small error in the stack throws the angle off.
- MechanicsSpring Combination Calculator (Series and Parallel)Combined stiffness of two or three springs in parallel and in series, and the deflection each arrangement gives under a load.
- MechanicsThermal Stress Calculator (Restrained Bar)Stress and force in a bar that cannot expand or contract when its temperature changes, from the material's modulus, expansion coefficient and the temperature change.
- MechanicsThick-Walled Cylinder Stress Calculator (Lamé Equations)Hoop, radial and axial stress in a thick tube, pressure vessel or gun barrel under internal and external pressure, with the stress through the wall drawn as a chart.
- MechanicsThin-Wall Pressure Vessel Stress Calculator (Cylinder and Sphere)Hoop and longitudinal stress in a thin-walled cylinder or sphere under internal pressure, the wall thickness needed for an allowable stress, and the highest pressure a given wall can take.
- MechanicsTorque Wrench Extension Calculator (Setting with an Extension or Crow's Foot)Setting to dial on a torque wrench so the bolt gets the torque you want when an extension is fitted in line with the wrench.
- MechanicsPipe Pressure Rating Calculator (Barlow)Working or burst pressure of a pipe from outside diameter, wall thickness and allowable stress.
- MechanicsBolt Shear Capacity CalculatorDesign shear and tension capacity of a bolt from its stress area, grade and the number of shear planes.
- MechanicsPress Brake Tonnage CalculatorBending force in kN and tonnes for air bending, plus minimum flange and the natural inside radius for the die.
- MechanicsPunching Force Calculator (Sheet Metal)Force a press needs to punch round holes in sheet metal, from the hole diameter, sheet thickness and the material's shear strength.
- MechanicsTurning Surface Roughness CalculatorTheoretical Ra and Rz from feed and tool nose radius, and the feed needed to hit a target roughness.
- MechanicsThree-Wire Thread Measurement Calculator (Pitch Diameter)The measurement you should read over three wires for a thread of known pitch diameter, the best wire size, and the pitch diameter from a measurement you took.
Engineering
Industrial and process engineering: OEE, takt time, capacity, efficiency, tolerances and unit-heavy technical work.
- EngineeringOEE CalculatorOverall equipment effectiveness with its three factors: availability, performance and quality.
- EngineeringTakt Time CalculatorThe pace a line must run at to meet customer demand, in seconds per unit.
- EngineeringProduction Capacity CalculatorUnits per shift, per hour and per week from cycle time, efficiency and machine count.
- EngineeringCost Per Unit CalculatorUnit cost of a batch, showing how much of it is fixed cost spread over the quantity.
- EngineeringDowntime Cost CalculatorThe cost of a stoppage, counting lost margin and the fixed costs that keep running.
- EngineeringFirst Pass Yield CalculatorShare of units that pass without rework, alongside the final yield.
- EngineeringScrap Cost CalculatorWhat a scrap rate costs per period and per year.
- EngineeringLabour Productivity CalculatorUnits per person-hour, units per person and the labour minutes each unit consumes.
- EngineeringDPMO CalculatorDefects per million opportunities, with defects per unit and yield.
- EngineeringCp and Cpk CalculatorProcess capability indices from the specification limits, the mean and the standard deviation.
- EngineeringAir Changes Per Hour CalculatorAir changes per hour for a room, the flow a target rate needs, and the time for one complete change.
- EngineeringMTBF and Availability CalculatorMean time between failures, availability and total downtime from run hours and failure count.
- EngineeringAutomation ROI CalculatorHow many years a robot cell or automatic machine takes to pay back from the labour and other savings it brings, with and without the discount rate, its net present value and its return over its life.
- EngineeringLine Balancing and Takt Time CalculatorTakt time, theoretical number of workstations and balance efficiency of an assembly line.
- EngineeringElectricity CO₂ Emissions CalculatorCarbon dioxide from electricity use, with comparisons to trees and car kilometres.
- EngineeringCapacity Utilisation CalculatorUtilisation rate, spare capacity and how fixed costs per unit change when you fill the plant.
- EngineeringEconomic Order Quantity CalculatorThe order size that balances ordering costs against holding costs, with the order frequency.
- EngineeringStock Cover CalculatorDays of stock remaining, the reorder point for a lead time, and how many days of margin are left.
- EngineeringDuct Velocity and Sizing CalculatorAir velocity in a rectangular duct, its equivalent round diameter, and the size a target velocity needs.
- EngineeringEnergy Cost per Part CalculatorElectricity consumed and paid for by each part produced, and the yearly total.
- EngineeringPneumatic Cylinder Sizing CalculatorThe smallest bore that delivers a given force at your pressure, the standard bore to order, its usual rod and the real force out and back.
- EngineeringPrincipal Stress and Mohr's Circle Calculator (Plane Stress)Principal stresses, maximum shear, von Mises and Tresca equivalent stress, and the stress on any rotated plane, from σx, σy and τxy.
- EngineeringPsychrometric CalculatorHumidity ratio, enthalpy, saturation pressure and density of moist air at a given state.
- EngineeringWind Turbine Power CalculatorElectrical output of a wind turbine at a given wind speed, the power in the wind and the Betz limit, with the turbine's power curve drawn.
- EngineeringCompressed Air Pressure Drop CalculatorThe pressure lost along a compressed air pipe for a given flow, length and inner diameter, the air speed inside it and the smallest pipe that keeps the loss within your limit.
- EngineeringInventory Turnover CalculatorHow many times a year stock is sold and replaced, and how many days of stock that represents.
- EngineeringLMTD Heat Exchanger CalculatorLog mean temperature difference, the heat duty it gives, and the area a 100 kW duty would need.
- EngineeringStaffing Requirement CalculatorHeadcount needed for a workload, allowing for real efficiency and absence.
- EngineeringControl Chart Limits CalculatorUpper and lower control and warning limits for a control chart, from the process mean and standard deviation.
- EngineeringDegree Days CalculatorHeating and cooling degree days for a period, and the energy a building of a given fabric would need.
- EngineeringCompressed Air Leak Cost CalculatorHow much free air a set of leaks lets out at your network pressure, the compressor power it takes and what that costs in electricity per year.
- EngineeringMachine Hour Rate CalculatorWhat one productive hour of a machine costs, split into depreciation, interest, floor space, maintenance and energy, plus its total cost per year.
- EngineeringRoom CO₂ Level Calculator (Ventilation)How high carbon dioxide builds up in a room with a given number of people and amount of fresh air, and how much ventilation keeps it at 1000 ppm.
- EngineeringVacuum Suction Cup CalculatorThe holding force a vacuum gripper needs for a part, the force on each cup, the smallest cup diameter and whether the cups you have in mind hold it.
- EngineeringCorrosion Rate Calculator (Weight Loss, mm/year and mpy)Corrosion rate from the weight a test coupon loses, in mm per year, mils per year and µm per year, with the wall left after a number of years and the years until it reaches a minimum.
- EngineeringEvaporative Cooler Calculator (Outlet Air Temperature)Temperature of the air leaving a direct evaporative cooler from the outdoor temperature, humidity and the effectiveness of the wet media.
- EngineeringFan Power Calculator (Shaft Power from Airflow and Pressure)Power a fan or blower needs on its shaft from the airflow, the pressure it must add and its efficiency, together with the power that actually reaches the air.
- EngineeringHydraulic Accumulator Sizing Calculator (Bladder, Piston and Diaphragm)The size of accumulator needed to deliver a given volume of oil between a low and a high working pressure, from the gas precharge, with the gas volumes at both ends.
- EngineeringPick and Place Cycle Time CalculatorThe cycle time of a pick-and-place move — down, grip, up, across, down, release, up and back — from the distances, top speed, acceleration and gripper times, with the parts per minute and per hour.
- EngineeringDittus-Boelter Heat Transfer CalculatorNusselt number and convective heat transfer coefficient for turbulent flow inside a tube.
- EngineeringStack Effect Calculator (Chimney Effect in Buildings and Flues)The pressure difference and the airflow that warm air rising in a building, stairwell or chimney creates between a low and a high opening, from the height and the two temperatures.
- EngineeringWeibull Reliability CalculatorChance that a component is still working after a given time, the share failed, the failure rate and the B10 life, from the Weibull shape and scale parameters.
- EngineeringHeat Exchanger Effectiveness (NTU) CalculatorEffectiveness, NTU, capacity ratio and duty of a counterflow heat exchanger.
- EngineeringPneumatic Cylinder Air Consumption CalculatorFree air consumption of a pneumatic cylinder in NL/min and m³/h, plus the push force it develops.
- EngineeringFin Efficiency CalculatorEfficiency and heat output of a straight rectangular fin from its thickness, length, material and air-side coefficient.
- EngineeringAir Receiver Size CalculatorThe receiver volume needed to cover a given air demand for a given time within an allowed pressure drop.
Construction & DIY
Concrete, paint, tiles, flooring, slopes, excavation and material quantities for real building jobs.
- Construction & DIYConcrete Volume CalculatorCubic metres and tonnes of concrete needed for a slab, with a waste allowance.
- Construction & DIYPaint CalculatorLitres of paint needed for a given wall area, number of coats and coverage rate.
- Construction & DIYTile CalculatorHow many tiles you need for an area, with a cutting allowance.
- Construction & DIYSlope and Gradient CalculatorSlope as a percentage, an angle, a ratio and the sloping length.
- Construction & DIYFlooring CalculatorHow many packs of flooring to buy for a room, including waste.
- Construction & DIYRoom Wall Area CalculatorWall area, floor area, perimeter and volume of a rectangular room.
- Construction & DIYGravel and Aggregate CalculatorTonnes and cubic metres of gravel for a given area and depth, with the cost.
- Construction & DIYBrick CalculatorNumber of bricks or blocks for a wall area, counting the mortar joint.
- Construction & DIYRoof Pitch CalculatorRoof angle, pitch percentage, rafter length and roof area per metre of length.
- Construction & DIYDrywall CalculatorSheets, screws, joint tape and compound for a plasterboard job, from the area and the sheet size.
- Construction & DIYExcavation Volume CalculatorTrench volume in place, loose spoil volume after bulking, weight and truck loads.
- Construction & DIYConcrete Mix CalculatorCement bags, sand and gravel for a given volume and mix ratio.
- Construction & DIYStair CalculatorNumber of steps, exact riser height, total run and the Blondel comfort value.
- Construction & DIYLand Plot Area Calculator (four sides)Area of an irregular four-sided plot from its four sides and one diagonal, in square metres, hectares and acres.
- Construction & DIYHeat Loss Through a Wall CalculatorHeat lost through a surface, the daily energy it costs and the price of that energy.
- Construction & DIYSwimming Pool Volume CalculatorPool volume in cubic metres and litres, plus the filtration turnover time.
- Construction & DIYWallpaper CalculatorHow many rolls of wallpaper a room needs, counted in full drops.
- Construction & DIYDrawing Scale ConverterTurn a measurement taken off a scale drawing into the real-world size.
- Construction & DIYPipe Volume and Weight CalculatorLitres per metre, total volume, pipe weight and the weight of what is inside, from the outside diameter and the wall thickness.
- Construction & DIYPlaster and Render CalculatorBags of plaster or render for a wall area at a given thickness.
- Construction & DIYRainwater Harvesting CalculatorRainwater you can collect from a roof in a year, and the average per day.
- Construction & DIYSuspended Ceiling CalculatorPanels, grid runners, edge trim and hangers for a suspended ceiling, from the room size and the panel size.
- Construction & DIYColumn Concrete CalculatorConcrete volume and mass, formwork area, main bars and stirrups for rectangular columns.
- Construction & DIYRoof Tiles CalculatorNumber of tiles for a pitched roof, from the plan dimensions and the pitch angle.
- Construction & DIYU-Value and Insulation CalculatorThermal transmittance and resistance of an insulation layer, from thickness and conductivity.
- Construction & DIYBackfill CalculatorHow much fill a trench needs once the pipe or structure is in, in loose volume, tonnes and truck loads.
- Construction & DIYRebar Weight CalculatorWeight of reinforcement bars from diameter, length and quantity.
- Construction & DIYShelf Sag CalculatorSag of a loaded shelf, its stiffness ratio, the load for a 1:250 limit and the span that would halve the sag.
- Construction & DIYBoard Feet CalculatorBoard feet in a piece of timber, the total for a batch, the volume in cubic metres, cost and rough weight.
- Construction & DIYTile Grout CalculatorKilograms of grout for a tiled area, from tile size, joint width and tile thickness.
- Construction & DIYWaterproofing CalculatorMembrane area, rolls, primer and litres of liquid waterproofing, including the upstand at the walls.
- Construction & DIYDecking Boards CalculatorHow many deck boards a terrace needs, plus total linear metres and joist count.
- Construction & DIYRadiator Output CalculatorThe real heat output of a radiator at your actual flow and return temperatures, against its catalogue rating.
- Construction & DIYRamp Length CalculatorHorizontal run, sloping length and angle of a ramp for a given rise and gradient.
- Construction & DIYWelded Mesh CalculatorSheets, mass per square metre and total weight of reinforcement mesh, with the lap between sheets taken off.
- Construction & DIYWind Load CalculatorDynamic wind pressure and the force on a flat surface, with the overturning moment about its base.
- Construction & DIYDrainage Fall CalculatorTotal fall over a pipe run for a given gradient, in millimetres, percent and mm per metre.
- Construction & DIYUnderfloor Heating Pipe CalculatorMetres of pipe and number of loops for an underfloor heating circuit.
- Construction & DIYAsphalt Tonnage CalculatorTonnes of asphalt to order for a driveway, path or road from its size, compacted thickness and density, with the number of truckloads.
- Construction & DIYFence Posts CalculatorPosts, panels, the exact spacing that results and the concrete needed to set them.
- Construction & DIYGate CalculatorLeaf width, pickets, frame and brace lengths, weight and the load each hinge carries.
- Construction & DIYMulti-Layer Wall R-Value CalculatorTotal thermal resistance and U-value of a three-layer wall, and how much of it the insulation contributes.
- Construction & DIYSkirting Board CalculatorMetres of skirting and number of lengths needed for a room, allowing for doorways.
- Construction & DIYHorizontal Cylindrical Tank Volume CalculatorLitres in a horizontal round tank from the depth of liquid, plus the percentage full.
- Construction & DIYSimply Supported Beam Reactions and Bending Moment CalculatorSupport reactions, maximum bending moment and where it occurs, shear and moment at any point, and the bending stress, for a beam with a point load and a uniform load — with the moment diagram.
- Construction & DIYInsulation Thickness Calculator (for a Target U-Value)How thick a layer of insulation must be to bring an existing wall, roof or floor down to a target U-value.
- Construction & DIYPost Hole Concrete Calculator (Fence and Deck Posts)How much concrete and how many bags you need to set fence, deck or pergola posts, from the hole size, depth and post size.
- Construction & DIYManning Open Channel Flow CalculatorFlow and velocity in a rectangular open channel, with the hydraulic radius and wetted area.
- Construction & DIYWood Movement CalculatorHow much a board changes width as its moisture content changes, with the gap to allow.
- Construction & DIYBridged U-Value Calculator (Timber Stud or Joist Wall, ISO 6946 Combined Method)U-value of a wall, roof or floor where timber studs or joists interrupt the insulation, by the ISO 6946 combined method, with the heat loss the studs add — drawn against the stud share.
- Construction & DIYComposite Wall Sound Insulation Calculator (Wall with Window, Door or Gap)The sound reduction of a wall made of several parts — wall, window, door, vent or open gap — from their areas and their own dB ratings, and which part lets most of the sound through.
- Construction & DIYConcrete Block CalculatorHow many blocks a wall takes, from its area and the block size you are using.
- Construction & DIYFooting Bearing Pressure Calculator (Eccentric Load, Middle Third Rule)Largest and smallest pressure under a rectangular footing carrying a vertical load and a moment, the eccentricity, how much of the base stays in contact, and the area for a pressure you choose.
- Construction & DIYPipe Offset Calculator (Travel, Run and Multiplier for 45° and 30° Bends)The length of the diagonal piece between two bends that moves a pipe or conduit sideways by a given offset, with the run it uses, the take-up and the multiplier — drawn to scale.
- Construction & DIYTruncated Pyramid Volume Calculator (Footings, Hoppers)Volume and weight of a truncated pyramid with rectangular top and bottom — a tapered concrete footing, a hopper or a spoil heap — with the cross-section drawn to scale.
- Construction & DIYStud Wall Calculator (Timber or Metal Framing)Number of studs and length of plates and timber for a framed partition wall in wood or metal profiles, from its length, height and stud spacing.
- Construction & DIYSurface Condensation and Mould Risk CalculatorTemperature of the inside face of a wall, window or corner on a cold day, and whether it will get condensation or mould at the room's humidity.
- Construction & DIYBaluster Spacing Calculator (Balusters, Pickets and Slats)How many balusters a stair or balcony guard needs so no gap exceeds the limit, and the exact gap and centre spacing that results, so they look evenly spaced.
- Construction & DIYConcrete Strength Gain Calculator (Strength at 3, 7, 14 Days by Eurocode 2 or ACI 209)The strength a concrete has reached at a given age as a share of its 28-day value, and how many days it takes to reach a share you choose, such as 70 % for striking formwork.
- Construction & DIYGlass Weight Calculator (Panes and Double Glazing)Weight of a pane or a double-glazing unit from its size and glass thickness, per unit, in total and per square metre.
- Construction & DIYLadder Angle Calculator (1-in-4 Rule)How far to set the foot of a ladder from the wall for the safe 1-in-4 angle, and the ladder length needed to reach a given height.
- Construction & DIYRankine Earth Pressure Calculator (Retaining Wall Thrust)Active and passive earth pressure coefficients and the horizontal thrust on a retaining wall per metre, from the soil's friction angle, unit weight and the wall height.
- Construction & DIYRational Method Runoff Calculator (Peak Flow for Drains and Culverts)Peak stormwater flow from a small catchment — a roof, car park, yard or field — from its runoff coefficient, rainfall intensity and area, in m³/s and L/s.
- Construction & DIYScreed and Self-Levelling Compound Calculator (Bags for a Floor)Kilos and bags of self-levelling compound or screed for a floor, using the average thickness of a layer that is thin at one end and thick at the other.
- Construction & DIYSilicone and Sealant Cartridge Calculator (Caulk for a Joint)How many cartridges of silicone, caulk or sealant a joint takes, from its width, depth and total length, and how many metres one cartridge runs.
- Construction & DIYSnow Load Weight Calculator (Roof)Weight of the snow lying on a roof, per square metre and in total, from the depth of snow and its density.
- Construction & DIYSolar Panel Row Spacing Calculator (Avoid Shading)Distance between rows of tilted solar panels so that one row does not shade the next at noon on the winter solstice, with the ground coverage ratio.
- Construction & DIYSpherical Tank Volume Calculator (Partly Filled)How much liquid a spherical tank holds at a given level, its total capacity and the free space left, with the level-to-volume curve drawn.
- Construction & DIYConcrete Maturity Calculator (Nurse–Saul Equivalent Age)The maturity index and equivalent age of curing concrete from the temperatures it went through, so a cold week can be compared with a warm one.
- Construction & DIYCutting Stock Calculator with Saw Kerf (How Many Pieces per Board)How many pieces of a given length you get from a board, bar or pipe once the width of the saw cut is counted, how many boards to buy, and the waste.
- Construction & DIYMass Law Sound Insulation CalculatorHow much airborne sound a single solid wall or panel blocks at a given frequency, from its mass per square metre, by the mass law.
- Construction & DIYPolygon Frame Miter Angle Calculator (Hexagon, Octagon and Other Frames)The saw angle and the piece lengths for a frame, planter or table top with any number of equal sides, from the width across the flats and the board width.
- Construction & DIYSoil Swell and Shrinkage Calculator (Bank, Loose and Compacted Volume)Convert a volume of soil between in the ground, loose as dug and compacted in a fill, from the swell and shrinkage percentages, and count the truck loads.
- Construction & DIYWindow Overhang Shading Calculator (Eaves, Pergola, Awning Depth)How far an overhang, pergola or awning must project to keep a window or wall in shade at a given sun position, and how deep the shade of your existing one reaches.
- Construction & DIYCable Sag CalculatorSag, end tension and developed length of a cable or wire strung between two supports at the same height.
Finance
Interest, loans, savings, inflation, margin, markup and VAT. Informational calculators, not financial advice.
- FinanceCompound Interest CalculatorFuture value of savings with compound interest and optional monthly contributions.
- FinanceDiscount CalculatorFinal price after a percentage discount, and how much you save.
- FinanceLoan Payment CalculatorMonthly instalment, total paid and total interest on a loan repaid in equal payments.
- FinanceVAT CalculatorAdd VAT to a net price and remove VAT from a gross price, both at once.
- FinanceInflation CalculatorWhat an amount of money will be worth in real terms after years of inflation, and what it would cost.
- FinanceProfit Margin CalculatorGross margin, profit and the equivalent markup from cost and selling price.
- FinanceSimple Interest CalculatorInterest and final amount when interest is not compounded.
- FinanceROI CalculatorReturn on investment as a total percentage and as an annualised rate.
- FinanceSavings Goal CalculatorHow much to put aside each month to reach a target amount by a chosen date.
- FinanceAmortisation Schedule CalculatorThe payment, and a year-by-year table of how much goes to interest, how much to capital, and what is left owing.
- FinanceMarkup CalculatorSelling price from a cost price and a markup percentage, with the resulting margin.
- FinanceHow Much Can I Borrow CalculatorMaximum loan from an income, a share of income you accept as an instalment, a rate and a term.
- FinanceMonthly Budget CalculatorAdd up where the money goes, see what is left, and find out what share of your income you actually keep.
- FinanceBreak-Even Point CalculatorHow many units you must sell to cover fixed costs, and the revenue that represents.
- FinanceIRR CalculatorThe internal rate of return of any series of cash flows, with the net present value and a warning when the answer is not unique.
- FinanceCAGR CalculatorThe steady yearly rate that turns one figure into another over a number of years, which is not the total growth divided by the years.
- FinanceReal Return CalculatorWhat an investment actually earns once inflation is taken out, and why subtracting the two numbers is not the same thing.
- FinanceAnnuity CalculatorWhat a stream of equal payments is worth today and what it adds up to at the end, paid at the start or the end of each period.
- FinanceFIRE CalculatorThe capital that would cover a year of your spending indefinitely, how far off it is, and how long the current pace takes to get there.
- FinanceOutstanding Loan Balance CalculatorHow much of a loan is still owed after a number of instalments, and how much capital has been repaid.
- FinanceTravel Budget CalculatorWhat a trip will cost in total, per person, per day and per person per day, with a margin for what always comes up.
- FinancePortfolio Return CalculatorThe weighted return of a whole portfolio, with each holding's weight, its contribution, and how concentrated the whole thing is.
- FinanceYield to Maturity CalculatorWhat a bond really returns if held to the end, counting both the coupons and the gain or loss against face value.
- FinanceCredit Card Payoff CalculatorMonths to clear a credit card balance at a fixed monthly payment, and the interest it costs.
- FinanceInterest Rate Conversion CalculatorTurn a rate quoted for one period into the equivalent for any other — monthly, annual, nominal, effective or continuous.
- Finance50/30/20 Budget CalculatorMonthly budget split into needs, wants and savings, with the shares adjustable.
- FinanceMonte Carlo Investment SimulatorA thousand possible futures for the same savings plan, showing the range of outcomes rather than a single false-precise number.
- FinanceBeta CalculatorHow much an investment moves with the market, with alpha, correlation and the R² that says whether the beta means anything.
- FinanceDoubling Time Calculator (Rule of 72)How long money takes to double at a given rate, exactly and by the rule of 72.
- FinanceMortgage Overpayment CalculatorMonths cut from a mortgage and interest saved by paying extra each month.
- FinanceDollar Cost Averaging CalculatorThe price you really paid when you invested the same amount at different prices, against the plain average of those prices.
- FinanceSalary Increase CalculatorNew salary after a raise, the yearly gain and whether the raise beats inflation.
- FinanceDeclining Balance Depreciation CalculatorWhat something is worth after a number of years when it loses the same percentage of its remaining value every year.
- FinanceEffective Annual Rate CalculatorConvert a nominal annual rate with periodic compounding into the true effective annual rate.
- FinanceRetirement Capital CalculatorProjected capital from current savings plus monthly contributions, and what it could pay out.
- FinanceDiscounted Payback Period CalculatorHow long an investment takes to pay for itself once future money is discounted, next to the plain payback for comparison.
- FinanceNet Present Value (NPV) CalculatorNet present value of a constant annual cash flow against an upfront investment.
- FinancePrice Per Square Metre CalculatorPrice per square metre with and without purchase costs, and how it compares with a reference for the area.
- FinanceEmergency Fund CalculatorHow large an emergency fund should be, the gap to it and how long it takes to fill.
- FinanceRental Yield CalculatorGross, net and vacancy-adjusted rental yield, the income after costs and the payback period.
- FinanceStock Profit Calculator (After Fees and Tax)Profit or loss on a share trade after buying and selling fees and tax on the gain, the return on the money invested and the break-even sell price.
- FinanceBinomial Option Pricing CalculatorOption value from a Cox-Ross-Rubinstein tree, including American early exercise, with Black-Scholes alongside for comparison.
- FinanceCoast FIRE CalculatorHow much you need invested today so that, without adding another cent, it grows into your FIRE number by the age you want to retire.
- FinancePayback Period CalculatorHow long an investment takes to pay for itself, after yearly running costs.
- FinancePresent Value CalculatorWhat a future amount of money is worth today at a given discount rate.
- FinanceSavings Withdrawal CalculatorMonthly income a lump sum can pay out over a fixed number of years before it runs out.
- FinanceStraight-Line Depreciation CalculatorAnnual depreciation, book value after n years and the total written off.
- FinancePerpetuity CalculatorWhat an income that never stops is worth today, with or without growth, and what capital a given income needs.
- FinanceDividend Yield CalculatorDividend yield, annual income from a holding, and the payout ratio.
- FinanceLate Payment Interest CalculatorInterest on an overdue invoice, the daily rate and the total now due.
- FinanceBond Price CalculatorPrice of a bond from its yield, with the current yield, the price as a percentage of par and the effect of a 1 % yield rise.
- FinanceTax-Equivalent Yield CalculatorThe yield a taxable investment must pay to match a tax-free one at your tax rate, and which of two offers leaves you more after tax.
- FinanceReal Return After Tax and Inflation CalculatorWhat a nominal return is actually worth once tax and inflation have both taken their share.
- FinanceSharpe Ratio CalculatorSharpe ratio of a portfolio, annualised from any period, with the excess return and the return a ratio of 1 would need.
- FinanceBlack-Scholes Option Price CalculatorEuropean call option price, with d₁, d₂, the discounted strike and the intrinsic value.
- FinanceCurrency Converter (Your Own Rate)Convert an amount at a rate you enter, and see what the margin really costs you.
- FinanceDebt-to-Income (DTI) Ratio CalculatorShare of your monthly income that goes on debt repayments, and how much room is left for a new loan payment under a chosen limit.
- FinanceRefinance Break-Even Calculator (When Does a New Loan Pay Off?)Monthly payment on the current and the new loan, how much you save each month, and how many months it takes for that saving to repay the refinancing costs.
- FinanceSavings Rate to Financial Independence Calculator (Years to Retire)How many years of saving a given share of your income it takes before your savings can cover your spending, from the savings rate, the real return and the withdrawal rate.
- FinanceWACC CalculatorWeighted average cost of capital, with the equity weight, the after-tax cost of debt, gearing and the tax shield.
- FinanceCAPM Cost of Equity CalculatorRequired return on equity from the risk-free rate, beta and the market return.
- FinanceNPV Calculator for Uneven Cash FlowsDiscount a whole series of cash flows, one figure per period, and see what the project is worth today.
- FinanceAltman Z-Score Calculator (Bankruptcy Risk)Altman's Z-score for a listed manufacturing company from five balance-sheet and income figures, with the safe, grey or distress zone and the five ratios behind it.
- FinanceBalloon Loan Calculator (Monthly Payment With a Final Lump Sum)Monthly payment of a loan that leaves a balloon payment due at the end, the payment you would make with no balloon, and the total interest.
- FinanceCash Conversion Cycle Calculator (DIO, DSO, DPO)Days a business waits between paying for stock and collecting from customers: days of inventory, days of sales outstanding, days payable, and the net cycle.
- FinanceCash-on-Cash Return and Cap Rate Calculator (Rental Property)The cash-on-cash return, cap rate, net operating income, mortgage payments and debt service coverage of a rental property, from the price, deposit, loan, rent and costs.
- FinanceDebt Service Coverage Ratio (DSCR) and Interest Coverage CalculatorHow many times a business or property covers its loan payments: the DSCR, the interest coverage ratio and debt ÷ EBITDA, with the margin left before payments become a struggle.
- FinanceDiscount Break-Even Volume Calculator (How Much More Must You Sell?)How much extra volume a price cut must bring to leave your gross profit unchanged: d ÷ (m − d), with the units you would need to sell.
- FinanceDuPont Analysis Calculator (ROE Breakdown)Splits a company's return on equity into profit margin, asset turnover and leverage, so you can see where a high or low ROE really comes from.
- FinanceEarly Payment Discount Calculator (2/10 Net 30)The real annual interest rate you pay by not taking a prompt-payment discount such as 2/10 net 30, plus what the discount saves on an invoice.
- FinanceEnterprise Value (EV) Calculator and EV/EBITDA MultipleThe enterprise value of a company — what it would cost to buy the whole business, debt included, less the cash you would get — and the EV/EBITDA, EV/EBIT and EV/sales multiples.
- FinanceLiquidity Ratios Calculator (Current, Quick and Cash Ratio)Current ratio, quick (acid-test) ratio and cash ratio from a balance sheet, plus working capital, to see if short-term debts are covered.
- FinanceLoan-to-Value (LTV) CalculatorLoan-to-value ratio of a mortgage, the deposit it implies, and the largest loan a lender's maximum LTV allows on a property.
- FinanceLoss Recovery Calculator (Gain Needed After a Loss)The percentage gain needed to get back to where you started after a loss, and how many years that takes at a given return.
- FinanceMargin Call Price Calculator (Buying Shares on Margin)The share price at which a broker will demand more money when you buy on margin, how far that is from your purchase price, and what a price move does to your own money.
- FinanceNet Revenue Retention (NRR) Calculator — Subscription BusinessesNet and gross revenue retention of a group of customers from their starting recurring revenue, the expansion, the downgrades and the cancellations, plus the NRR over a year.
- FinanceOption Payoff Calculator (Call and Put, Long and Short)Profit or loss of a call or put option held to expiry, bought or sold, with its break-even price, from the strike, the premium and the share price at expiry.
- FinanceP/E Ratio Calculator (Price to Earnings, Earnings Yield, PEG)Price-to-earnings ratio, earnings yield and PEG ratio of a share from its price, earnings per share and expected growth.
- FinancePosition Size CalculatorHow many shares or units to buy so that, if the stop-loss is hit, you lose no more than a chosen percentage of the account.
- FinanceRights Issue TERP Calculator (Theoretical Ex-Rights Price)Theoretical share price after a rights issue, the value of each right, the factor that restates old prices, and what it costs to take up your entitlement.
- FinanceStartup Dilution Calculator (Funding Round, Pre- and Post-Money)How much of the company you own after a funding round, from your stake, the pre-money valuation, the new investment and any option pool created, with the value of what remains.
- FinanceAverage Cost Calculator (Average Price After a Second Purchase)Average price per share after buying more, the total invested, the gain or loss at the current price and the price needed to break even after fees.
- FinanceValue at Risk (VaR) Calculator (Parametric, With Expected Shortfall)The loss a portfolio is not expected to exceed over a few trading days at a chosen confidence level, and the average loss in the cases beyond it, assuming normal returns.
- FinanceKelly Criterion CalculatorThe fraction of a bankroll to stake for maximum long-run growth, with half-Kelly and the break-even probability.
- FinanceBond Accrued Interest Calculator (Clean and Dirty Price)Interest a bond has earned since its last coupon, the full-coupon amount, and the dirty price a buyer actually pays on top of the quoted clean price.
- FinanceEconomic Value Added (EVA) Calculator (NOPAT, ROIC and Capital Charge)Profit left after paying for all the capital a business uses, plus NOPAT, the return on invested capital and how far it sits above or below the cost of capital.
- FinanceEquivalent Annual Cost (EAC) Calculator — Compare Assets With Different LivesThe true yearly cost of two machines, vehicles or appliances with different prices, running costs and lifetimes, so the cheaper one over time is clear.
- FinanceForward Exchange Rate Calculator (Covered Interest Parity)The forward rate of a currency pair from the spot rate, the two interest rates and the number of days, with the forward points and the annualised premium or discount.
- FinancePrice Increase to Keep Your Margin CalculatorThe new selling price that keeps your margin percentage when costs go up, and the smaller price that only keeps the same profit in money per unit.
- FinanceMIRR Calculator (Modified Internal Rate of Return)The modified internal rate of return of a project with up to five years of cash flows, assuming inflows are reinvested at one rate and outflows are financed at another.
- FinancePrice Elasticity of Demand CalculatorHow strongly sales reacted to a price change, whether demand is elastic or inelastic, and what happened to revenue.
- FinanceSaaS Rule of 40, Magic Number and Burn Multiple CalculatorThree quick efficiency checks for a software or subscription company: the Rule of 40 score, the sales-efficiency magic number and the burn multiple.
- FinanceSortino Ratio and Calmar Ratio CalculatorTwo risk-adjusted performance ratios that only count the bad risk: Sortino divides the excess return by the downside deviation, Calmar divides the return by the worst peak-to-trough fall.
- FinanceTrading Expectancy Calculator (Win Rate, Payoff Ratio, Profit Factor)Average result per trade from the win rate and the average win and loss, with the profit factor, the break-even win rate and the expected total over many trades.
- FinanceTreasury Bill Yield Calculator (Discount Rate to Price and Yield)Price of a discount security such as a Treasury bill from its quoted discount rate, with the bond-equivalent, money-market and effective annual yields.
- FinanceTreynor Ratio, Jensen's Alpha and M² CalculatorThree ways to judge a portfolio's return against its risk: Jensen's alpha, the Treynor ratio and the Modigliani M², from the portfolio and market returns, beta and volatility.
- FinanceTwo-Stage Dividend Discount Model CalculatorWhat a share is worth today if its dividend grows fast for some years and then settles into slower, steady growth, with how much of that value sits beyond the fast years.
- FinanceBond Duration and Convexity CalculatorMacaulay and modified duration plus convexity, summed from the actual cash flows, with what a one-point rate move does to the price.
- FinanceMortgage Points Break-Even CalculatorWhether paying for discount points to lower a loan's rate is worth it: the payment with and without them, and how many months it takes to recover their cost.
- FinanceOverhead Absorption Rate Calculator (Predetermined Rate and Variances)Hourly overhead rate set from the budget, overhead charged to production at the actual hours, and the under- or over-absorption split into spending and volume variances.
- FinanceRule of 78 Calculator (Early Loan Payoff Interest Refund)How much of a precomputed loan's interest is refunded when you settle early under the Rule of 78, and how much more the lender keeps than with an even spread.
- FinanceStandard Cost Variance Calculator (Material and Labour Price, Usage and Efficiency)Material price and usage variances and labour rate and efficiency variances from standard and actual figures, with the total difference from the standard cost.
- FinanceSum-of-the-Years'-Digits Depreciation Calculator (Accelerated Method)Depreciation expense, accumulated depreciation and book value of an asset in any year using the sum-of-the-years'-digits method, next to the straight-line charge.
- FinanceSustainable Growth Rate Calculator (ROE, Retention and Internal Growth)The fastest a company can grow sales without issuing shares or changing its leverage, from its return on equity and the share of profit it keeps, plus the internal growth rate.
Physics
Motion, forces, energy, momentum, rotation, waves, light and radioactivity — the physics formulas used in school and at work.
- PhysicsSpeed, Distance and Time CalculatorFill in any two of speed, distance and time and get the third.
- PhysicsKinematics CalculatorGive any three of starting speed, final speed, acceleration, time and distance, and the other two come out.
- PhysicsAcceleration CalculatorAverage acceleration from a change in speed over a time, with the distance covered.
- PhysicsFriction Force CalculatorThe force friction is actually applying, what it takes to break an object free, and how far it slides to a stop.
- PhysicsInclined Plane CalculatorThe forces on a slope: what pulls down it, what presses into it, whether it slides, and the force to hold or raise it.
- PhysicsCollision CalculatorThe speeds after a collision, elastic, inelastic or anywhere in between, with the energy that survives and the energy that does not.
- PhysicsKinetic Energy CalculatorEnergy of a moving object, plus the height it would have to fall to gain the same energy.
- PhysicsRope Tension CalculatorThe tension in a rope for the four cases that come up: hanging, in a lift, over a pulley, and shared between two ropes.
- PhysicsMoment of Inertia CalculatorRotational inertia for the standard shapes, with the parallel axis theorem, radius of gyration and stored energy.
- PhysicsFree Fall CalculatorDistance fallen and speed reached after a given time of free fall.
- PhysicsCentre of Mass CalculatorThe balance point of several masses along a line or across a plane, with each one's share of the total.
- PhysicsWork and Power CalculatorWork done by a force over a distance, and the power that implies over a time.
- PhysicsSpherical Mirror CalculatorWhere a concave or convex mirror puts the image, how big it is, and whether it is real, virtual, upright or inverted.
- PhysicsPotential Energy CalculatorGravitational potential energy at a height, and the speed it converts into.
- PhysicsSound Level and Distance CalculatorSound level at a new distance, the intensity and pressure behind it, and the level from several identical sources.
- PhysicsTime Dilation and Length Contraction CalculatorLorentz factor at a given fraction of light speed, with the stretched time, the shortened length and the kinetic energy.
- PhysicsDrag Force Calculator (Air Resistance)Aerodynamic drag on a car, bike or any object at a given speed, the power needed to overcome it and the energy it costs per 100 km.
- PhysicsHalf-Life CalculatorQuantity remaining after radioactive decay, the number of half-lives elapsed and the decay constant.
- PhysicsHooke's Law Spring CalculatorForce in a spring at a given extension, the energy stored, the sag under a mass and the natural frequency.
- PhysicsWavelength CalculatorWavelength from frequency and wave speed, including the quarter-wave length.
- PhysicsMass-Energy Equivalence CalculatorEnergy locked in a given mass, expressed in joules, kilowatt-hours and tonnes of TNT.
- PhysicsMomentum and Impulse CalculatorMomentum of a moving mass, and the force needed to change it in a given time.
- PhysicsProjectile Range CalculatorHow far, how high and for how long a projectile travels, from launch speed and angle.
- PhysicsCoulomb's Law CalculatorElectrostatic force between two point charges, the field of the first, and their potential energy.
- PhysicsGravitational Force CalculatorAttraction between two masses and the acceleration the larger one produces.
- PhysicsPhotoelectric Effect CalculatorMaximum kinetic energy and speed of the electrons knocked out of a metal by light, the stopping voltage, and the threshold wavelength and frequency.
- PhysicsBanked Curve Speed CalculatorDesign speed of a banked curve with no friction, the maximum speed with grip, and the flat-road limit.
- PhysicsDoppler Effect CalculatorFrequency heard as a source approaches and as it recedes, with the shift in hertz and semitones.
- PhysicsThin Lens Equation CalculatorImage distance, magnification and image height for a thin lens, plus its optical power in dioptres.
- PhysicsMagnetic Field Around a Wire Calculator (Ampère's Law)Magnetic field at a given distance from a straight wire carrying a current, in microtesla and gauss, compared with the Earth's field.
- PhysicsEscape Velocity CalculatorSpeed needed to escape a body's gravity, and the speed needed to orbit it at the surface.
- PhysicsSnell's Law Refraction CalculatorAngle of refraction between two media, the critical angle and the speed of light in each.
- PhysicsLorentz Force CalculatorMagnetic force on a moving charge, the radius it curves through and its cyclotron frequency.
- PhysicsPhoton Energy CalculatorEnergy of a photon from its wavelength, in electronvolts, attojoules and kilojoules per mole.
- PhysicsSpeed of Sound CalculatorSpeed of sound in air at a given temperature, the travel time over a distance and the echo rule.
- PhysicsAngular Momentum CalculatorAngular momentum and rotational energy, and the new speed if the moment of inertia changes.
- PhysicsPendulum Period CalculatorSwing period and frequency of a simple pendulum, plus the length for a one-second period.
- PhysicsForce on a Current-Carrying Wire CalculatorForce a magnetic field exerts on a wire carrying current, in total and per metre.
- PhysicsStanding Wave and Harmonics CalculatorResonant frequency of a string or open pipe at a chosen harmonic, and the closed-pipe frequency alongside.
- PhysicsBeat Frequency and Tuning CalculatorBeat rate between two close frequencies, the time between beats, and the interval in cents.
- PhysicsBounce Height Calculator (Coefficient of Restitution)Height of a ball after any number of bounces, the total distance and time until it stops, and the coefficient of restitution from a drop test.
- PhysicsElectromagnetic Wave Speed Calculator (Maxwell)Speed of an electromagnetic wave in a material, its velocity factor, refractive index, wavelength and wave impedance from εr and µr.
- PhysicsGauss's Law Calculator (Charged Sphere)Electric field, potential and flux at any distance from a charged sphere, inside or outside it, with the field profile drawn.
- PhysicsLensmaker's Equation CalculatorFocal length and power of a lens from its glass, the two radii of curvature and the thickness, in air or in another medium.
- PhysicsGravitational Time Dilation Calculator (GPS Clocks)How many microseconds per day a clock gains at altitude from weaker gravity, how many it loses to orbital speed, and the net drift of a clock in that orbit.
- PhysicsClimbing Fall Factor and Impact Force CalculatorFall factor of a lead fall and an idealised estimate of the peak force on the climber, from the fall length, the rope out and the rope's rated impact force.
- PhysicsOptical Fibre Numerical Aperture CalculatorNumerical aperture, acceptance angle, V number and single-mode cut-off of a step-index optical fibre from its core and cladding indices.
- PhysicsApparent Depth Calculator (Why Pools Look Shallow)How deep water looks from above compared with how deep it really is, and the size of Snell's window — the circle of sky a diver or fish sees overhead.
- PhysicsDecibel Addition Calculator (Combining Sound Levels)Combined sound level of two, three or four sources of different loudness, and how much louder the total is than the loudest one.
- PhysicsDiffraction Grating Calculator (Angles of the Orders and Spot Positions)Angles at which a diffraction grating sends a given wavelength in the first three orders, the highest order that exists, and where the spots land on a screen.
- PhysicsDouble-Slit Interference Calculator (Young's Experiment)Fringe spacing, the angle of the first bright fringe and the brightness anywhere on the screen, with the whole interference pattern drawn.
- PhysicsFloating Draft Calculator (Barge, Pontoon, Flat-Bottom Boat)How deep a flat-bottomed box, pontoon or barge sits in the water for a given load, the freeboard left, and the most it can carry before the water reaches the deck.
- PhysicsMagnifier Calculator (Magnifying Glass Power from Focal Length)Magnification of a magnifying glass or loupe from its focal length, in both common conventions, with its power in dioptres — or the focal length for a stated magnification.
- PhysicsPlanck's Law Calculator (Black-Body Spectrum)Spectral radiance of a black body at any wavelength and temperature, its peak and total emission, with the whole spectrum drawn against a second temperature.
- PhysicsRolling Down an Incline Calculator (Sphere, Cylinder, Hoop Race)Acceleration, speed at the bottom and time for a sphere, cylinder or hoop rolling down a slope, and the friction needed so it does not slip.
- PhysicsDe Broglie Wavelength CalculatorThe matter wavelength of a particle from its mass and speed, in metres, nanometres and picometres.
- PhysicsAdiabatic Compression and Expansion Calculator (Ideal Gas)Final temperature, pressure and work when an ideal gas is compressed or expanded so quickly that no heat flows in or out, with the isothermal result for comparison.
- PhysicsBallistic Pendulum Calculator (Speed of a Projectile)Speed of a bullet or ball from how far a hanging block swings after catching it, with the height risen and the share of energy lost in the impact.
- PhysicsFresnel Equations Calculator (Reflectance and Brewster Angle)How much light a surface between two materials reflects at any angle, for each polarisation, with the Brewster and critical angles and the full curve drawn.
- PhysicsGravity at Latitude and Altitude Calculator (Local g)The acceleration of gravity at your latitude and height above sea level, how much a given mass weighs there and how fast the Earth's rotation carries you along.
- PhysicsHelmholtz Coil CalculatorMagnetic field along the axis of a pair of coaxial coils, how uniform it is around the middle, and the field profile of each coil drawn.
- PhysicsGas Molecule Speed and Mean Free Path Calculator (Kinetic Theory)How fast the molecules of a gas move at a given temperature, three ways of averaging it, and how far a molecule travels between collisions.
- PhysicsMalus's Law Calculator (Polarisers)Light intensity after one, two or three polarisers at any angles, with the classic three-polariser surprise shown on the chart.
- PhysicsNuclear Binding Energy Calculator (Mass Defect and Energy per Nucleon)The energy that holds a nucleus together, from its measured atomic mass: the mass defect, the total binding energy in MeV and the binding energy per nucleon.
- PhysicsPoiseuille Flow Calculator (Hagen–Poiseuille Law for Tubes and Blood Vessels)Flow rate of a thick liquid through a narrow tube from the pressure difference, tube size, length and viscosity, with a check that the flow is smooth enough for the law to hold.
- PhysicsRadiation Pressure and Solar Sail CalculatorForce, pressure and acceleration that sunlight produces on a sail at a given distance from the Sun, for any reflectivity and tilt.
- PhysicsRainbow and Halo Angle Calculator (Why 42° and 22°)The angle from the point opposite the Sun at which the primary and secondary rainbows appear for red and violet light, the dark band between them, and the 22° halo of ice crystals.
- PhysicsRelativistic Kinetic Energy CalculatorKinetic energy, Lorentz factor and momentum of an object moving at a sizeable fraction of the speed of light, compared with Newton's ½mv².
- PhysicsRelativistic Velocity Addition CalculatorCombined speed of an object moving inside a moving frame, by Einstein's formula, compared with the simple sum.
- PhysicsThin Film Interference Calculator (Soap Bubbles, Oil Slicks, Anti-Reflection Coatings)Wavelengths a thin film of a given thickness and refractive index reflects most strongly, the thinnest film that makes or cancels a reflection, and its brightness at one wavelength.
- PhysicsCapillary Rise Calculator (Jurin's Law)How high a liquid climbs, or is pushed down, in a narrow tube from its surface tension, the contact angle, the density and the tube radius.
- PhysicsCompton Scattering CalculatorEnergy and wavelength of a photon after bouncing off an electron, the energy the electron takes, and the Compton edge and backscatter peak of a gamma line.
Heat & Fluids
Pressure, buoyancy, pipe flow and head loss, specific and latent heat, conduction, convection, radiation and the gas laws — the two halves of thermofluids, each stating the law it comes from.
- Heat & FluidsDensity CalculatorFill in any two of mass, volume and density and get the third.
- Heat & FluidsHeat Conduction CalculatorHeat flow through a solid layer by Fourier's law, with the thermal resistance and what it costs over a day and a year.
- Heat & FluidsLatent Heat CalculatorThe energy needed to melt or boil something, and how long a given heater would take to do it.
- Heat & FluidsPipe Flow Velocity CalculatorFlow velocity inside a pipe from the flow rate and the internal diameter.
- Heat & FluidsHeat Energy CalculatorEnergy needed to change the temperature of a mass, in megajoules and kilowatt-hours.
- Heat & FluidsContinuity Equation CalculatorHow fast a fluid speeds up when the pipe narrows, with the flow rate, the areas and the pressure it trades away.
- Heat & FluidsConvection Heat Transfer CalculatorHeat carried away from a surface by air or water, from Newton's law of cooling, with the area or coefficient you would need.
- Heat & FluidsFirst Law of Thermodynamics CalculatorThe change in internal energy from the heat going in and the work coming out, with the temperature change it implies.
- Heat & FluidsHydrostatic Pressure CalculatorPressure at a depth in a liquid, as gauge pressure and as absolute pressure.
- Heat & FluidsReynolds Number CalculatorReynolds number for pipe flow, the critical speed and an estimated friction factor.
- Heat & FluidsThermal Expansion CalculatorHow much a bar, rail or pipe grows when its temperature rises.
- Heat & FluidsBernoulli Equation CalculatorDownstream pressure from upstream conditions, with the velocity and height contributions shown separately.
- Heat & FluidsDarcy-Weisbach Head Loss CalculatorFriction head loss and pressure drop along a pipe, with the flow rate and the power it costs.
- Heat & FluidsCarnot Efficiency CalculatorMaximum theoretical efficiency of a heat engine between two temperatures, plus the ideal COP of a fridge and a heat pump.
- Heat & FluidsTerminal Velocity CalculatorSteady falling speed at which air resistance exactly balances weight.
- Heat & FluidsBuoyancy CalculatorUpthrust on a submerged body, the net weight in the fluid and how much of it floats below the surface.
- Heat & FluidsHydronic Water Flow Rate Calculator (Heating and Chilled Water, kW to m³/h)The water flow a heating or cooling load needs for a chosen temperature difference, and the pipe diameter or the velocity that flow gives — drawn against ΔT.
- Heat & FluidsIdeal Gas Law CalculatorAmount of substance from pressure, volume and temperature, with the molar volume.
- Heat & FluidsWater Properties Calculator (Density, Viscosity, Surface Tension vs Temperature)Density, dynamic and kinematic viscosity, surface tension and specific weight of liquid water between 0 and 100 °C — the numbers you need for a Reynolds number or a pump calculation.
- Heat & FluidsStefan-Boltzmann Radiation CalculatorHeat radiated by a hot surface, the net loss to its surroundings and the wavelength it peaks at.
- Heat & FluidsWien's Displacement Law CalculatorWavelength at which a hot body radiates most strongly, with the matching frequency and photon energy.
- Heat & FluidsPipe Friction Factor CalculatorThe Darcy friction factor from pipe diameter, wall roughness and Reynolds number, using the Swamee-Jain equation.
- Heat & FluidsAir Compressor Power Calculator (Polytropic, Multistage with Intercooling)Shaft power, the isothermal minimum, isothermal efficiency and discharge temperature of an air compressor from inlet flow, pressures, polytropic exponent, efficiency and number of stages.
- Heat & FluidsHeating Expansion Vessel Sizing CalculatorVolume of the expansion vessel for a closed heating or chilled-water circuit, from the system water volume, the fill and maximum temperatures and the pressures — with the water's expansion worked out from its density.
- Heat & FluidsMixing Temperature Calculator (Final Temperature of Two Substances)The temperature two amounts of water, or any two substances, settle at when mixed or put in contact, and the heat that moves between them.
- Heat & FluidsPipe Insulation Heat Loss CalculatorHeat lost by a hot pipe with and without insulation, the saving, the energy wasted per day and the critical insulation radius, with the cross-section drawn to scale.
- Heat & FluidsPump Operating Point Calculator (Pump Curve Meets System Curve)The flow and head a pump will really deliver in a given pipe system, from its shut-off head and one rated point and the system's static head and friction loss, with both curves drawn.
- Heat & FluidsTank Draining Time Calculator (Torricelli)How long a vertical cylindrical tank takes to empty through a hole in its bottom, the level at any moment and the flow at the start, with the tank drawn to scale.
- Heat & FluidsValve Kv and Cv Calculator (Flow Coefficient, Valve Sizing)The Kv or Cv a valve needs for a given liquid flow and pressure drop, the flow a valve of known Kv passes, and the drop it gives at your flow — with the flow-against-pressure curve.
- Heat & FluidsHazen-Williams Head Loss CalculatorHead loss, pressure drop and velocity in a water pipe from flow rate, diameter, length and the C roughness coefficient.
- Heat & FluidsFroude Number Calculator (Open Channel Flow Regime)Froude number of flow in a channel, a river or a spillway from the speed and depth, with whether the flow is subcritical or supercritical and the critical depth.
- Heat & FluidsHeat Recovery Ventilation Calculator (Supply Temperature and Energy Saved)Temperature of the fresh air leaving a heat-recovery ventilation unit, the heat it recovers and the heating still needed, and the efficiency from a measured temperature.
- Heat & FluidsIsentropic Flow Calculator (Mach Number, Static and Stagnation Properties)Static pressure, temperature, density, speed and area ratio of a compressible gas flow at a given Mach number, from its stagnation conditions.
- Heat & FluidsOtto Cycle Calculator (Petrol Engine Efficiency, Temperatures and Mean Effective Pressure)Efficiency, peak temperature and pressure, net work and mean effective pressure of the ideal air-standard Otto cycle, from compression ratio, intake state and heat added.
- Heat & FluidsStokes Settling Velocity Calculator (Sedimentation of Particles)How fast a small sphere sinks (or rises) through a fluid by Stokes' law, with its Reynolds number, whether the law applies, and the time to settle a given height.
- Heat & FluidsV-Notch Weir Calculator (Triangular Weir Flow)Flow over a sharp-crested V-notch weir from the notch angle and the head of water above its vertex, in litres per second and cubic metres per hour.
- Heat & FluidsWater Hammer Calculator (Joukowsky Pressure Surge)Pressure rise when a flow is stopped suddenly in a pipe, from the change in speed, the pressure-wave speed and the density, with the critical closing time.
- Heat & FluidsCOP, EER and kW/ton ConverterConvert coefficient of performance, energy efficiency ratio and kilowatts per ton of refrigeration.
- Heat & FluidsCooling Tower Make-Up Water Calculator (Evaporation, Blowdown, Cycles of Concentration)Water a cooling tower evaporates, bleeds off and must be topped up with, from the circulating flow, the cooling range and the cycles of concentration.
- Heat & FluidsFlue Gas Loss Calculator (Siegert Formula, Boiler Combustion Efficiency)Heat lost up the chimney as a percentage of the fuel's energy, and the combustion efficiency, from the flue gas temperature, the oxygen reading and the fuel.
- Heat & FluidsRectangular Weir Flow Calculator (Francis Formula)Flow over a sharp-crested rectangular weir from the crest length and the head of water above it, with the effect of end contractions.
- Heat & FluidsThermal Conductivity ConverterConvert W/(m·K), BTU/(h·ft·°F), BTU·in/(h·ft²·°F) and kcal/(h·m·°C).
- Heat & FluidsCooling Time Calculator (Lumped Capacitance)Temperature of a part after a given time in air or a bath, plus its thermal time constant and Biot number.
- Heat & FluidsHeat Transfer Coefficient ConverterConvert W/(m²·K), BTU/(h·ft²·°F) and kcal/(h·m²·°C).
Chemistry
Concentrations, dilutions, gas laws, pH and buffers, reaction yields and rates, each one stating the law it comes from.
- ChemistrySolution Dilution Calculator (C₁V₁ = C₂V₂)Volume of stock solution needed to make a given volume at a lower concentration.
- ChemistryMolar Mass CalculatorType a chemical formula and get its molar mass, with a breakdown of what it is made of.
- ChemistryPercent Yield CalculatorReaction yield as a percentage of the theoretical maximum, with the loss and the moles involved.
- ChemistrySoap Lye Calculator (Sodium Hydroxide for Cold Process Soap)Grams of sodium hydroxide and water for a batch of cold-process soap from the weight and saponification value of each oil, the superfat and the water ratio.
- ChemistryTitration CalculatorUnknown concentration from a titration, plus the moles and the mass of analyte in the sample.
- ChemistryPPM Concentration CalculatorParts per million converted to mg/L, percent, ppb, total mass and molarity.
- ChemistryLimiting Reagent CalculatorWhich of two reagents runs out first, how much of the other is left over, and how far the reaction goes.
- ChemistryMass Percent Concentration CalculatorPercent by mass of a solution, converted to grams per litre, molarity and parts per million.
- ChemistryHenderson-Hasselbalch Buffer CalculatorpH of a buffer from its pKa and the ratio of conjugate base to weak acid.
- ChemistryPool Chemical Dosing Calculator (Alkalinity, Calcium Hardness, Stabiliser)How much sodium bicarbonate, calcium chloride or cyanuric acid to add to raise a pool's alkalinity, calcium hardness or stabiliser from today's reading to the one you want.
- ChemistryWater Hardness Calculator (mg/L, °dH, °f, °Clark, gpg)Total hardness of tap water from its calcium and magnesium, in mg/L of CaCO₃ and in German, French, English and American degrees, with its class.
- ChemistryCombined Gas Law CalculatorNew volume of a fixed amount of gas after a change of pressure and temperature, with the ratio and the moles present.
- ChemistryFreezing Point Depression CalculatorHow far a dissolved substance lowers the freezing point of a solvent.
- ChemistryMolality CalculatorMoles of solute per kilogram of solvent, with the mole fraction and mass percent.
- ChemistryBeer-Lambert Law CalculatorAbsorbance from concentration and path length, the transmittance it corresponds to, and the concentration giving A = 1.
- ChemistryMolarity CalculatorMolar concentration of a solution from the mass of solute, its molar mass and the volume.
- ChemistryOsmotic Pressure CalculatorOsmotic pressure of a solution in kilopascals, atmospheres and bar, with its osmolarity.
- ChemistryBoiling Point Elevation CalculatorHow far a dissolved substance raises the boiling point of a solvent.
- ChemistryFirst-Order Kinetics CalculatorConcentration remaining after a given time, the half-life and the time to reach 90 % conversion.
- ChemistryLangelier Saturation Index Calculator (Pool and Water Balance)Whether pool or tap water will dissolve metal and plaster or leave limescale, from pH, temperature, dissolved solids, calcium hardness and alkalinity.
- ChemistrypH CalculatorpH and pOH from the hydrogen ion concentration of a solution.
- ChemistryPriming Sugar Calculator (Bottle Carbonation for Beer and Cider)Grams of sugar to add to a batch before bottling to reach a target carbonation, from the volume, the fermentation temperature and the type of sugar.
- ChemistryArrhenius Equation CalculatorRate constant at two temperatures, how much faster the reaction gets, and the ten-degree factor.
- ChemistryFaraday Electrolysis CalculatorMass deposited or dissolved by a current over time, with the charge passed and the moles involved.
- ChemistryNernst Equation CalculatorCell potential away from standard conditions, the slope per decade, the Gibbs energy and the equilibrium constant.
- ChemistryAtom Economy CalculatorAtom economy of a reaction, the fraction lost to by-products, the reaction mass efficiency and the E factor.
- ChemistryCentrifuge RCF to RPM Calculator (g-Force)Relative centrifugal force in × g for a given rotor speed and radius, and the rpm needed to reach a protocol's g-force on your rotor.
- ChemistryGibbs Free Energy CalculatorGibbs free energy change, equilibrium constant and crossover temperature from enthalpy and entropy changes.
- ChemistryConcentrated Acid Molarity Calculator (HCl, H₂SO₄, HNO₃ Stock Solutions)Molarity of a concentrated acid or other stock solution from its percentage and density, and how much of it to measure out to make a dilute solution.
- ChemistryWeak Acid pH CalculatorpH of a solution of a weak acid such as acetic, citric or formic acid from its pKa and concentration, solved exactly rather than by the usual shortcut.
- ChemistryGraham's Law of Effusion CalculatorHow many times faster one gas escapes through a tiny hole than another, from their molar masses, and how long the second gas takes for the same amount.
- ChemistrySerial Dilution CalculatorFinal concentration after a series of equal dilution steps, with the dilution factor and log reduction.
- ChemistryBuffer Preparation Calculator (Henderson-Hasselbalch, Grams to Weigh Out)The ratio of conjugate base to acid for a target pH, and the moles and grams of each to weigh out for a given volume and total concentration.
- ChemistryClausius–Clapeyron Calculator (Vapour Pressure and Boiling Point)Vapour pressure of a liquid at another temperature, and its boiling point at another pressure, from one known point and the enthalpy of vaporisation.
- ChemistryHenry's Law Calculator (Dissolved Gas, Fizzy Drinks, Aquariums)Amount of gas dissolved in a liquid at a given pressure from Henry's constant, and how much comes out when the pressure drops, as when a bottle is opened.
- ChemistryReaction Order Calculator (Method of Initial Rates)Order of a reaction with respect to one reactant from two experiments with different starting concentrations, plus the rate constant and the predicted rate at another concentration.
- ChemistryChromatography Resolution Calculator (Rs, Plate Number, Retention Factor)Resolution between two chromatographic peaks, with the plate number, plate height, retention factor and selectivity, from retention times and base widths.
- ChemistryIonic Strength and Activity Coefficient Calculator (Debye–Hückel, Davies)Ionic strength of a solution from its ions' concentrations and charges, the activity coefficient of an ion by the limiting law and the Davies equation, and the Debye length.
- ChemistryKp to Kc Conversion Calculator (Equilibrium Constants of Gas Reactions)Converts the equilibrium constant of a gas reaction between concentration form Kc and pressure form Kp for a given temperature and change in moles of gas.
- ChemistryMolar Solubility from Ksp CalculatorMolar solubility and grams per litre of a sparingly soluble salt from its solubility product, for any formula AxBy.
- ChemistryRydberg Equation CalculatorWavelength, frequency and photon energy of a hydrogen emission line from the two energy levels involved.
- ChemistryMole and Particle ConverterConvert moles, millimoles, micromoles and numbers of atoms or molecules.
- ChemistryVan der Waals Equation CalculatorPressure of a real gas from the Van der Waals equation, compared with the ideal gas value.
- ChemistryBragg's Law CalculatorDiffraction angle from lattice spacing, wavelength and order, plus the 2-theta value read off a diffractometer.
- ChemistryDegree of Unsaturation Calculator (Double Bond Equivalents)Number of rings plus double bonds (and twice the triple bonds) in an organic molecule from its molecular formula.
- ChemistryRaoult's Law Calculator (Vapour Pressure of a Mixture)Vapour pressure of an ideal mixture of two liquids and the composition of the vapour above it, from the mole fraction and the pure vapour pressures.
- ChemistrySecond-Order Reaction Kinetics CalculatorConcentration left after a given time in a second-order reaction, its half-life and the time to reach 90 % conversion.
- ChemistryAntoine Equation Vapour Pressure CalculatorVapour pressure of a liquid at a given temperature from its Antoine constants, in mmHg, kPa and bar.
- ChemistryAtomic Energy Unit ConverterConvert hartree, electronvolt, rydberg, kJ/mol, kcal/mol and wavenumbers.
Science
Astronomy, earth science, biology and the environment: distances between stars, earthquake energy, population growth and air quality.
- ScienceEquivalent Exposure CalculatorChange the aperture or the ISO and get the shutter speed that keeps the exposure exactly the same, with the stops shown.
- ScienceEquivalent Focal Length CalculatorCrop factor, equivalent focal length, equivalent aperture and equivalent ISO for any sensor size.
- ScienceDistance Between Coordinates CalculatorGreat-circle distance between two points on Earth in kilometres, miles and nautical miles, with the initial bearing.
- ScienceSunrise and Sunset CalculatorClock times of sunrise and sunset and the length of the day for any place and day of the year, with how the day length changes through the year.
- ScienceAstrophotography Exposure CalculatorThe longest exposure before stars trail, by the 500 rule, the 600 rule and the NPF rule, with the trail length in pixels.
- ScienceDew Point CalculatorDew point from temperature and relative humidity, with the vapour pressure and absolute humidity.
- ScienceLight Travel Time CalculatorHow long light takes to cross a distance, in seconds, minutes, light years and astronomical units.
- ScienceHeat Index CalculatorApparent temperature in hot, humid weather, with how much above the real temperature it feels.
- ScienceReverberation Time CalculatorRT60 by Sabine and by Eyring, with the room volume, total absorption, Schroeder frequency and critical distance.
- ScienceDaylight Hours CalculatorLength of daylight at a latitude on a given day of the year, with the solar declination and noon sun height.
- ScienceRoom Modes CalculatorThe lowest standing-wave frequencies of a rectangular room, sorted, with each one marked axial, tangential or oblique.
- ScienceEarthquake Energy CalculatorEnergy released by an earthquake in joules and tonnes of TNT, and how it compares with another magnitude.
- ScienceTelescope Magnification CalculatorMagnification from an eyepiece, with the exit pupil, true field of view, useful maximum and limiting magnitude.
- ScienceAltitude Pressure CalculatorAir pressure, temperature, boiling point and oxygen partial pressure at altitude.
- ScienceDistance to the Horizon CalculatorHow far the horizon is from any height, with and without atmospheric refraction, and how far away a tall object stays visible.
- ScienceMoon Phase CalculatorPhase of the Moon, its age and how much of the disc is lit on any date, with the days to the next full and new moon.
- ScienceSun Position and Shadow Length CalculatorHeight and direction of the Sun at any clock time, place and day, the length of a shadow, and the Sun's path through the day drawn against the solstices.
- ScienceFlight Carbon Footprint CalculatorGreenhouse gas emissions of a flight per passenger, with and without the high-altitude multiplier.
- ScienceLight Meter CalculatorTurn a meter reading in cd/m² or lux into a shutter speed, for incident or reflected metering, using the ISO 2720 constants.
- ScienceMacro Magnification and Bellows CalculatorMagnification, bellows exposure factor, effective aperture and working distance from the focal length and the extension.
- SciencePopulation Growth CalculatorPopulation after a number of years at a continuous growth rate, with the doubling time.
- ScienceBacterial Growth CalculatorCell count after a period of exponential growth, the number of generations and the time to reach a million per millilitre.
- ScienceCrosswind Component CalculatorCrosswind and headwind components for a wind at an angle to the runway, with the margin to a stated limit.
- ScienceDiffraction Limit CalculatorAiry disk diameter, the f-number where diffraction reaches the pixel pitch, and whether it is visible yet.
- ScienceKepler's Third Law CalculatorOrbital period and speed of a body from its orbital radius and the mass it orbits.
- ScienceWeight on Other Planets Calculator (and Your Age There)What you would weigh on the Moon, Mars, Jupiter or any other planet, how high you could jump, and how old you would be in that world's years.
- ScienceCircle of Confusion CalculatorThe circle of confusion for a sensor, by the diagonal rule or from the print size and how sharp you want the print to look.
- ScienceRocket Equation Calculator (Delta-v)Delta-v from specific impulse and the wet and dry masses of a stage, with mass ratio and propellant load.
- ScienceStar Luminosity CalculatorLuminosity of a star in solar units and watts, its peak colour, absolute magnitude and the flux reaching us.
- ScienceStar Magnitude CalculatorBrightness ratio between two magnitudes, and the absolute magnitude of a star at a given distance.
- ScienceEarthquake Epicentre Distance CalculatorDistance to an earthquake from the delay between the P and S waves on a seismogram.
- ScienceReciprocity Failure CalculatorThe corrected exposure time for film at long exposures, by the Schwarzschild law, including any filter stops.
- ScienceApparent Temperature Calculator ('Feels Like', Steadman)How warm or cold it feels from the air temperature, humidity and wind together, with the formula used by the Australian Bureau of Meteorology.
- ScienceBeaufort Scale Converter (Wind Force)Beaufort wind force and its name from a wind speed, with the speed in metres per second, knots and miles per hour.
- ScienceLightning Distance Calculator (Flash to Thunder)How far away a lightning strike was from the seconds between the flash and the thunder, with the speed of sound corrected for temperature.
- ScienceLogistic Growth Calculator (S-Curve with a Carrying Capacity)Population, or any quantity with a ceiling, after a given time, how close it is to the limit, and how long it takes to reach half and 90 % of it.
- ScienceWet-Bulb Temperature Calculator (from Temperature and Humidity)Wet-bulb temperature from the air temperature and relative humidity with Stull's formula, and how far below the air temperature it sits.
- ScienceWind Speed at Height Calculator (Wind Shear, Power Law and Log Law)Wind speed at another height from a measurement at one height, by the power law and by the logarithmic law, for turbine hub heights, masts and anemometers.
- ScienceSchwarzschild Radius CalculatorThe event horizon radius for a given mass, in metres and kilometres, with the mean density inside it.
- ScienceAngular Size Calculator (Apparent Size of the Moon, a Building, a Star)How big an object looks, as an angle in degrees and arcminutes, from its real size and distance — or the real size from the angle it covers.
- ScienceCloud Base Calculator (from Temperature and Dew Point)Estimated height of the base of cumulus clouds from the air temperature and dew point at the ground.
- ScienceDarcy's Law Calculator (Groundwater Flow, Seepage Velocity, Travel Time)Flow of water through soil or rock from its hydraulic conductivity, the head difference and the path length, with the real seepage velocity and the time a tracer needs.
- ScienceLength of a Degree of Latitude and Longitude CalculatorHow many kilometres one degree of latitude and one degree of longitude span at your latitude, and how many degrees a given distance is, on the WGS84 ellipsoid.
- ScienceDensity Altitude CalculatorThe altitude your aircraft, engine or propeller 'feels' on a hot or low-pressure day, from field elevation, QNH and temperature.
- ScienceHargreaves Reference Evapotranspiration Calculator (ET₀ from Temperature)Daily water use of a well-watered reference grass in mm per day, from only the day's highest and lowest temperature, the latitude and the date.
- ScienceHumidex Calculator (Canadian Heat and Humidity Index)The humidex — how hot and humid weather feels — from the air temperature and the dew point, with the Canadian comfort category and the vapour pressure.
- ScienceOcean Wave Calculator (Wavelength, Speed and Power)Wavelength, speed, group speed and power of ocean waves from their period, the water depth and the wave height, solving the full dispersion relation.
- ScienceCO₂ Radiative Forcing and Climate Sensitivity CalculatorThe extra heating a change in carbon dioxide concentration puts on the climate, in W/m², and the warming it commits to once the climate settles, for a chosen climate sensitivity.
- ScienceRadiocarbon Age Calculator (Carbon-14 Dating)Conventional radiocarbon age from the share of carbon-14 left in a sample, and the age with the modern half-life.
- ScienceRedshift and Hubble's Law Distance CalculatorDistance of a galaxy from its redshift using Hubble's law, with the recession speed, the shifted wavelength of a spectral line and the Hubble time.
- ScienceReturn Period Calculator (100-Year Flood and Earthquake Risk)The chance of at least one flood, storm or earthquake of a given return period during the years you care about, and the return period a design needs to keep the risk acceptably low.
- ScienceRoche Limit Calculator (How Close a Moon Can Orbit Before Tides Tear It Apart)Distance inside which the tides of a planet or star would pull a moon, comet or spacecraft apart, for a fluid body and for a rigid one, from the two densities.
- ScienceSea-Level Pressure Calculator (Home Weather Station Pressure Correction)The sea-level pressure that matches the reading of a barometer at your altitude, so it can be compared with forecasts and weather maps, which always quote pressure reduced to sea level.
- ScienceStar Altitude and Azimuth Calculator (RA/Dec to Horizon Coordinates)Altitude and compass bearing of a star, planet or galaxy at a given moment from its right ascension and declination, your latitude and the local sidereal time.
- ScienceTree Height Calculator (Clinometer Method)The height of a tree, pole or building from your distance to it, the angle up to its top and your eye height.
- ScienceTsunami Speed and Arrival Time CalculatorHow fast a tsunami crosses the ocean for a given depth, how long it takes to arrive, its wavelength and how much taller it grows as it slows near the coast.
- ScienceVapor Pressure Deficit Calculator (VPD for Greenhouses and Grow Rooms)The vapour pressure deficit of the air, and at the leaf, from the air temperature and relative humidity — the number growers use to judge how hard plants are transpiring.
- ScienceHill Sphere CalculatorRadius of the region where a planet or moon, rather than the body it orbits, controls what circles around it.
- ScienceHohmann Transfer CalculatorThe two burns, total delta-v and travel time to move between two circular orbits.
- ScienceHardy-Weinberg Carrier Frequency CalculatorAllele frequencies, carrier frequency and genotype proportions from the frequency of the recessive phenotype.
- ScienceAirmass Calculator (Atmospheric Extinction of Stars and the Sun)How much atmosphere the light of a star or the Sun crosses at a given altitude above the horizon, and how much that dims it, using the Kasten–Young formula.
- ScienceCritical Distance Calculator (Room Acoustics)The distance from a loudspeaker or talker at which the direct sound and the room's reverberation are equally loud, from the room volume, RT60 and the source's directivity.
- ScienceDive Gas Consumption Calculator (SAC / RMV)How much gas a dive at a given depth and time uses, the cylinder pressure left, and the longest bottom time that keeps your reserve.
- ScienceElliptical Orbit Calculator (Period, Eccentricity and Speed at Any Point)Orbital period, eccentricity and the speed at the closest, farthest and any chosen point of an elliptical orbit around the Sun, Earth, the Moon, Mars or Jupiter.
- ScienceExoplanet Transit Calculator (Depth, Duration and Probability)How much a planet dims its star as it crosses the disc, how long the crossing lasts and how likely a random observer is to see it, from the sizes, the orbital period and the star's mass.
- ScienceGeostrophic Wind Calculator (Wind from Isobar Spacing and Coriolis)The wind speed that balances the pressure gradient against the Coriolis force, from the spacing of isobars on a weather chart, the latitude and the air density.
- ScienceNitrox MOD and EAD CalculatorMaximum operating depth of an enriched-air (nitrox) mix, its equivalent air depth for decompression, and the best mix for a planned depth.
- SciencePlanet Equilibrium Temperature CalculatorThe temperature a planet or moon settles at from the light of its star alone, from the star's luminosity, the distance and how much light the planet reflects.
- ScienceQ10 Temperature Coefficient CalculatorHow much faster a biological or chemical process runs when the temperature rises, using the Q10 coefficient — or the Q10 itself from two measured rates.
- ScienceRadioactive Activity Calculator (from Mass and Half-Life)Activity in becquerels and curies of a given mass of a radioactive isotope, its specific activity, and how the activity falls over time.
- ScienceRadiometric Age Calculator (Uranium–Lead, Potassium–Argon, Rubidium–Strontium)Age of a rock or mineral from the ratio of daughter to parent atoms for the uranium–lead, potassium–argon and rubidium–strontium clocks, with the share of the parent isotope left.
- ScienceSeawater Freezing Point CalculatorThe temperature at which seawater of a given salinity starts to freeze, at the surface or at depth, from the UNESCO equation.
- ScienceSeismic Moment and Moment Magnitude Calculator (Mw from Fault Size and Slip)The moment magnitude of an earthquake from the size of the fault that ruptured, the average slip and the rigidity of the rock, with the seismic moment.
- ScienceSeismic Refraction Depth Calculator (Crossover Distance and Intercept Time)Depth to a faster layer, such as bedrock or the water table, from the wave speeds of the two layers and the crossover distance or intercept time on a travel-time graph.
- ScienceSpecific Gravity Calculator for Minerals and Gemstones (Hydrostatic Weighing)Specific gravity, density and volume of a mineral, rock or gemstone from its weight in air and its weight hanging in water, plus its weight in carats.
- ScienceStrike and Dip from Three Points Calculator (Three-Point Problem)Dip, dip direction and strike of a plane — a bed, a fault or a contact — from the coordinates and elevations of three points on it, such as boreholes or outcrops.
- ScienceSynodic Period Calculator (Time Between Oppositions and Conjunctions)How often two bodies line up again as seen from the star or planet they orbit — the time between Mars oppositions, Venus conjunctions or two full moons — from their two orbital periods.
- ScienceSpeed of Sound in Seawater Calculator (Mackenzie Equation, Echo Sounders and Sonar)How fast sound travels in water of a given temperature, salinity and depth, the water depth that an echo time corresponds to and the error of a sounder fixed at 1500 m/s.
- ScienceUnderwater Sound Transmission Loss Calculator (Spreading and Thorp Absorption)How much an underwater sound weakens over a distance, split into geometric spreading and absorption by seawater (Thorp), and the level that reaches the listener.
- ScienceMichaelis-Menten Enzyme Kinetics CalculatorReaction rate, fraction of Vmax and catalytic efficiency from Vmax, Km and substrate concentration.
- ScienceAstronomical Distance ConverterConvert astronomical units, light-years, parsecs, kilometres and solar radii.
- ScienceAiry Isostasy Calculator (Mountain Roots)How deep the crust extends into the mantle under a mountain, and how thick it is in total, if the mountain floats in balance like an iceberg.
- ScienceApparent Dip Calculator (and True Thickness of a Dipping Bed)The dip of beds seen in a cross-section that is not at right angles to the strike, and the true thickness of a dipping layer from a vertical borehole or from its outcrop width.
- ScienceHalf-Value Layer Calculator (Radiation Shielding)How much X-ray or gamma radiation gets through a shield of a given thickness, and how thick it must be to cut it to a target, from the half-value layer.
- ScienceSidereal Time Calculator (Local Sidereal Time)Local and Greenwich sidereal time for any date, time and longitude — the right ascension crossing your meridian, for pointing a telescope.
- ScienceRadiation Dose Converter (Sievert and Rem)Convert sievert, millisievert, microsievert, rem and millirem.
- ScienceRadioactivity ConverterConvert becquerel, curie, disintegrations per minute and rutherford.
- ScienceAbsorbed Dose Converter (Gray and Rad)Convert gray, milligray, kilogray, rad and erg per gram.
Time & Dates
Date differences, age, working days, time arithmetic, deadlines and duration conversions.
- Time & DatesAge CalculatorExact age in years, months and days, plus the days, hours and minutes lived and when the next birthday falls.
- Time & DatesDays Between Dates CalculatorExact number of days, weeks, months and hours between two dates.
- Time & DatesHours Between Two TimesWorked hours from a start time, an end time and a break, in decimal and in hours and minutes.
- Time & DatesStopwatchA stopwatch with lap times, showing the elapsed time in seconds, minutes and hours at once.
- Time & DatesWorking Days CalculatorNumber of weekdays between two dates, both dates included.
- Time & DatesCountdown TimerCounts down to a moment, in days, hours, minutes and seconds, and keeps counting past it.
- Time & DatesPregnancy Due Date CalculatorThe estimated due date from the first day of the last menstrual period, by Naegele's rule.
- Time & DatesAdd or Subtract Days from a DateThe date a given number of days before or after a start date.
- Time & DatesWorld ClockFour clocks side by side, each on its own UTC offset, ticking together with UTC itself.
- Time & DatesFlight Arrival Time CalculatorWhat time you land in local time, and whether it is still the same day, from the departure time, the two time zones and the flight length.
- Time & DatesHours and Minutes to DecimalConvert a duration in hours, minutes and seconds into decimal hours.
- Time & DatesTime Zone Difference CalculatorThe local time somewhere else from a time here and the two UTC offsets, with the day shift.
- Time & DatesAdd Hours and MinutesSum of two durations in hours and minutes, in decimal hours, and the difference between them.
- Time & DatesAdd Working Days CalculatorThe date a given number of working days from a start date, skipping weekends.
- Time & DatesWeek Number and Date InfoISO week number, weekday, day of the year and quarter for any date.
- Time & DatesFlight Duration CalculatorThe real time in the air between two local clock times in two different time zones, with the day change accounted for.
- Time & DatesCalendar GeneratorAny month laid out as a grid, starting on Monday or on Sunday, with the working days and weekend days counted.
- Time & DatesWeek Number to DatesWhich Monday to Sunday a given ISO week number covers, and how many weeks that year holds.
- Time & DatesEaster Date Calculator (and Carnival, Good Friday, Corpus Christi)Date of Easter Sunday in any year from 1583, with the movable holidays that depend on it and the Orthodox Easter date.
- Time & DatesDaylight Saving Time Dates Calculator (When Do the Clocks Change?)The dates when daylight saving (summer) time starts and ends in a given year in the United States and Canada, or in the European Union and the United Kingdom.
- Time & DatesGregorian to Hijri Date Converter (Islamic Calendar)The Hijri (Islamic) year, month and day for a Gregorian date, using the standard arithmetical (tabular) Islamic calendar.
- Time & DatesNth Weekday of the Month Calculator (4th Thursday of November, Last Monday of May)The date of the first, second, third, fourth or last given weekday of a month in any year — the way many holidays and deadlines are defined.
- Time & DatesOrthodox Easter Date Calculator (Pascha) for Any YearThe Gregorian date of Orthodox Easter in a given year, how many days after Western Easter it falls, and the same day in the Julian calendar the Church uses to compute it.
- Time & DatesInternational Meeting Time PlannerFind the hours that suit two or three time zones at once, using the UTC offsets you enter.
- Time & DatesJulian Day ConverterTurn a calendar date into a Julian day number, Julian date or Modified Julian date, and back again.
Work & Productivity
Text counting, case conversion, timesheets, hourly rates, random data and small office utilities.
- Work & ProductivityWord and Character CounterCount words, characters, sentences, paragraphs and reading time as you type.
- Work & ProductivityPassword GeneratorGenerates random passwords from the character sets you choose, with the entropy in bits.
- Work & ProductivityHourly Pay CalculatorGross pay from hours worked, hourly rate and overtime at a premium.
- Work & ProductivitySalary ConverterTurn an annual salary into monthly, weekly, daily and hourly figures.
- Work & ProductivityColour PickerPick a colour and get it back as five tints and shades, ready to paste into a stylesheet.
- Work & ProductivityLorem Ipsum GeneratorPlaceholder paragraphs of any length, with the classic opening if you want it.
- Work & ProductivityColour Palette GeneratorBuilds a five-colour palette from one base colour using the classic harmony schemes.
- Work & ProductivityText Case ConverterSwitch text between upper, lower, title, sentence, snake and kebab case.
- Work & ProductivityUUID GeneratorVersion 4 UUIDs in the standard 8-4-4-4-12 form, ready to paste.
- Work & ProductivityAspect Ratio CalculatorResize an image or video while keeping its proportions, with the simplified ratio.
- Work & ProductivityColour ConverterHex, RGB and HSL for a colour, with its complementary and the contrast against black and white.
- Work & ProductivityColour Contrast CheckerThe WCAG contrast ratio between two colours, and whether it passes AA or AAA at the text size you are using.
- Work & ProductivityGrade Needed CalculatorThe mark you need on the final assessment to reach a target average.
- Work & ProductivityInvoice Line Total CalculatorLine total with quantity, unit price, a discount and VAT, showing each step.
- Work & ProductivityText Difference CheckerPut two versions of a text side by side and see exactly which lines were added, removed or left alone.
- Work & ProductivityUsername GeneratorReadable usernames made from two word lists, with or without a trailing number.
- Work & ProductivityFind and ReplaceSwap one piece of text for another everywhere it appears, with control over capitals and whole words.
- Work & ProductivityFreelance Rate CalculatorThe hourly and day rate you need to charge to reach a target income.
- Work & ProductivityTime Card CalculatorHours worked between two clock times, less the break, with the pay and the weekly total.
- Work & ProductivityDecision Matrix CalculatorScore several options against several criteria, weight the criteria by how much each one matters, and get a ranking instead of an argument.
- Work & ProductivityDaily Target CalculatorHow much you have to do each day to finish on time, how long your current pace would actually take, and how far the two are apart.
- Work & ProductivityExtract from TextPull every email address, link, number, hashtag or mention out of a block of text, with the duplicates removed.
- Work & ProductivityPIN GeneratorRandom numeric PINs of any length, with how many combinations exist and the entropy.
- Work & ProductivityEisenhower Matrix GeneratorSort a list of tasks into do now, give it a date, hand it over and let it go, from an urgency mark and an importance mark.
- Work & ProductivityTrue Cost of an EmployeeYearly and monthly cost of a salary once employer contributions and extras are included.
- Work & ProductivityReadability CalculatorThe Flesch Reading Ease score and the school grade it corresponds to, with the sentence and syllable measurements behind them.
- Work & ProductivityText CleanerTidies pasted text in one go: extra spaces, ragged ends and blank lines all removed.
- Work & ProductivityTest Score CalculatorExam percentage from correct answers, the mark on any scale, and how many answers a pass needs.
- Work & ProductivitySales Commission CalculatorCommission above a sales threshold, total pay with the base, and the effective rate on all sales.
- Work & ProductivityOvertime Pay CalculatorTotal pay across normal hours and two overtime bands, with the effective average rate.
- Work & ProductivityText Similarity CheckerHow alike two texts are, letter by letter and by the words they share, with the exact number of edits between them.
- Work & ProductivityTime Allocation CalculatorDivide the hours you actually have between the things you want to do, in proportion to how much each one matters.
- Work & ProductivityWord Frequency CounterHow many times each word appears in a text, from the most common down, with its share of the whole.
- Work & ProductivityHoliday Entitlement CalculatorHow many days off you have earned so far this year, how many you have left, and what a full year would give you.
- Work & ProductivityRemove Empty LinesTake the blank lines out of a block of text and leave everything else exactly as it was.
- Work & ProductivitySort Text LinesPuts a list of lines in alphabetical order, reverse order, or from shortest to longest.
- Work & ProductivityTyping Speed CalculatorGross and net words per minute from a timed passage, with accuracy and characters per minute.
- Work & ProductivityMeeting Cost CalculatorWhat a meeting costs in salary terms, per occurrence and per year.
- Work & ProductivityRemove Duplicate LinesStrips repeated lines from a list and tells you how many went.
- Work & ProductivityPassword Entropy CalculatorEntropy in bits for a random password of a given length and alphabet, with a brute-force time estimate.
- Work & ProductivitySubnet Mask CalculatorUsable hosts, total addresses and the four octets of the subnet mask for a CIDR prefix.
- Work & ProductivityRemove Duplicate WordsKeep the first appearance of every word and throw the repeats away, ignoring capitals and punctuation.
- Work & ProductivityRemove Extra SpacesCollapses runs of spaces and tabs to one and trims the ends of every line.
- Work & ProductivityFile Transfer Time CalculatorTime to send or receive a file over a connection, allowing for real-world overhead.
- Work & ProductivityVideo File Size CalculatorFile size of a video from its bitrate and length, the recording time on a card, and the bitrate that would fill it exactly.
- Work & ProductivityConversion Rate and ROAS CalculatorConversion rate, revenue, cost per conversion and return on ad spend from one set of numbers.
- Work & ProductivityRemove Line BreaksJoins a text broken across many lines back into one flowing paragraph.
- Work & ProductivityBurn Rate and Runway CalculatorMonths of cash remaining, the net monthly burn and how much of costs revenue already covers.
- Work & ProductivityPomodoro PlannerHow many focus blocks a task needs, the real time it takes with breaks, and the share of that time spent working.
- Work & ProductivityRender Time CalculatorHow long a render will take on a given number of machines, with the total frames, the cost and the real speedup.
- Work & ProductivityBillable Utilisation Rate CalculatorShare of hours that are billable, and the effective rate once unbillable time is included.
- Work & ProductivityPERT Three-Point Estimate CalculatorExpected duration from optimistic, likely and pessimistic estimates, with confidence ranges.
- Work & ProductivityCPM, CPC and CTR Calculator (Advertising)Cost per thousand impressions, cost per click and click-through rate of an ad campaign from its spend, impressions and clicks.
- Work & ProductivityDimensional (Volumetric) Weight Calculator for ShippingVolumetric weight of a parcel from its size and the carrier's divisor, the chargeable weight (the greater of that and the real weight), the total volume, and which one you will be billed on.
- Work & ProductivityFTE Calculator (Full-Time Equivalent, Pro-Rata Pay and Headcount)Full-time equivalent of a part-time schedule, the pro-rata pay, the FTE of a group, and how many people or FTEs are needed to cover a weekly workload.
- Work & ProductivityNPS Calculator (Net Promoter Score)Net Promoter Score from the counts of promoters, passives and detractors, with each group's share and the margin of error of the score.
- Work & ProductivityPaper Weight (GSM) CalculatorWeight of a sheet and of a whole ream, from the sheet size and grammage.
- Work & ProductivityReverse TextWrites a text backwards, character by character.
- Work & ProductivityRoll Length CalculatorLength of material on a roll from its outside and core diameters, with the number of turns, area and weight.
- Work & ProductivityBreak-Even ROAS Calculator (Maximum Ad Cost per Order)The return on ad spend you need just to break even on an order, the most you can pay to win one, and the ROAS and cost per order that leave a target profit.
- Work & ProductivityCustomer Lifetime Value (LTV) CalculatorHow much gross profit an average subscriber brings in before leaving, how long they stay, and how that compares with what it costs to acquire them.
- Work & ProductivityBoxes per Pallet Calculator (Layers, Height and Weight Limits)How many boxes of a given size fit on a pallet, from boxes per layer, layers under the height limit and the weight limit, with the load weight and surface covered.
- Work & ProductivityQueue Waiting Time Calculator (M/M/1)Average wait, queue length and time in the system for a single counter, checkout or server with random arrivals, from the arrival and service rates.
- Work & ProductivityEarned Value Calculator (CPI, SPI, EAC)Cost and schedule performance of a project from its budget, planned value, earned value and actual cost, with the forecast cost at completion.
- Work & ProductivityEmployee Turnover Rate CalculatorStaff turnover for any period and annualised, from the number of leavers and the headcount at the start and end.
- Work & ProductivityErlang C Calculator (Call Centre Staffing and Service Level)How well a given number of agents will answer incoming calls: the service level, the chance a caller waits, the average wait and the occupancy, from call volume and handling time.
- Work & ProductivityFree Space Path Loss CalculatorPath loss and received signal level for a radio link, from distance, frequency, power and antenna gains.
- Work & ProductivityGMROI Calculator (Gross Margin Return on Inventory Investment)How much gross margin each unit of money tied up in stock earns in a period, with the gross margin, its percentage of sales and the stock turns behind it.
- Work & ProductivityLittle's Law Calculator (WIP, Throughput, Lead Time)Lead time, work in progress or throughput of any process from the other two, by Little's law — fill in the two you know.
- Work & ProductivityMarketing Funnel Calculator (How Many Visitors Do I Need?)Works backwards from the number of customers you want through each conversion step to the visitors, leads and budget required, with the cost per customer and the return on spend.
- Work & ProductivityOperating Leverage Calculator (DOL and Margin of Safety)How sensitive profit is to sales: the degree of operating leverage, the break-even point and the margin of safety from units, price, variable cost and fixed costs.
- Work & ProductivityRICE Score Calculator (Prioritise Features and Projects)Scores and compares two ideas with the RICE method — reach, impact, confidence and effort — so you can see which to do first.
- Work & ProductivityBreak-Even Calculator for Several Products (Sales Mix)The number of units to sell to cover fixed costs when you sell up to three products in a fixed proportion, using the average contribution of the mix.
- Work & ProductivitySprint Forecast Calculator (Agile Velocity and Delivery Date)How many sprints and weeks the rest of a backlog will take from your team's velocity, allowing for scope that keeps being added, with best and worst cases.
- Work & ProductivityStandard Time Calculator (Time Study: Normal Time, Rating and Allowances)Normal and standard time per cycle from the observed time, the operator's performance rating and the allowance, with the output per hour that standard allows.
- Work & ProductivityWSJF Calculator (Weighted Shortest Job First Prioritisation)Weighted Shortest Job First score for two backlog items from their value, time criticality, risk reduction and size, showing which one to do first.
- Work & ProductivityReorder Point and Safety Stock CalculatorThe stock level at which to order again, and how much buffer to hold against a bad week.
- Work & ProductivityShannon Channel Capacity CalculatorThe theoretical maximum error-free data rate of a channel from its bandwidth and signal-to-noise ratio.
- Work & ProductivityEconomic Production Quantity (EPQ) CalculatorThe best batch size for items you make yourself — balancing set-up cost against holding cost while stock builds up gradually — with the cycle, run length and yearly cost.
- Work & ProductivityKanban Card Calculator (How Many Kanbans for a Loop)Number of kanban cards or containers needed to keep a production line supplied, from the demand, the replenishment lead time, a safety allowance and the container size.
- Work & ProductivityLearning Curve Calculator (Wright's Law, Time per Unit)How the average time per unit falls as repetitive work is repeated, from the first-unit time and the learning rate, with the total time and the number of units to reach a target.
- Work & ProductivityNewsvendor Model Calculator (How Much to Order for Uncertain Demand)The best quantity to order for a product you can only buy once before demand is known, from the price, cost, leftover value and the average and spread of demand.
- Work & ProductivityViral Coefficient (K-Factor) CalculatorThe viral coefficient of a product or referral scheme from invitations sent and the share that convert, with the users it brings in over a number of cycles.
- Work & ProductivityFresnel Zone CalculatorRadius of the first Fresnel zone at any point along a radio path, and the 60% clearance normally required.
- Work & ProductivityBradford Factor Calculator (Absence)The Bradford factor used by many employers to measure short, frequent absences, from the number of separate absences and the total days.
Developers
JSON, CSV, XML, Base64, URL and HTML tools, minifiers, regular expressions and timestamps. Everything runs in your browser.
- DevelopersQR Code GeneratorMakes a QR code from any text or link, entirely in your browser.
- DevelopersJSON FormatterIndents, sorts or minifies JSON, keeping every number exactly as you wrote it.
- DevelopersUnix Timestamp ConverterConverts between Unix time and a readable UTC date, in both directions.
- DevelopersBase64 EncoderEncodes text to Base64, handling accents and any other UTF-8 correctly.
- DevelopersRegex TesterRuns a regular expression against text and shows every match and capture group.
- DevelopersBase64 DecoderDecodes Base64 back to text, with or without padding, plain or URL-safe.
- DevelopersJSON ValidatorSays whether a JSON document is valid and, if not, exactly where it breaks.
- DevelopersURL EncoderPercent-encodes text so it can be dropped safely into a URL or a query string.
- DevelopersJSON to CSV ConverterTurns a JSON array of objects into a comma-separated table you can open in a spreadsheet.
- DevelopersURL DecoderTurns a percent-encoded link back into readable text, UTF-8 included.
- DevelopersCSV to JSON ConverterTurns a CSV table into a JSON array of objects, guessing numbers and booleans.
- DevelopersMarkdown to HTML ConverterTurns Markdown into clean HTML, with everything escaped safely first.
- DevelopersCSS MinifierStrips comments and needless whitespace from a stylesheet, safely.
- DevelopersQR Code CustomizerThe same QR code with your own colours, module size and quiet zone, as a downloadable SVG.
- DevelopersHTML EncoderEscapes the five characters that would otherwise be read as markup.
- DevelopersBarcode GeneratorCode 128 and EAN-13 barcodes as SVG, with the check digit worked out for you.
- DevelopersURL ParserBreaks a link into scheme, host, port, path, query parameters and fragment.
- DevelopersHTML DecoderTurns HTML entities back into the characters they stand for.
- DevelopersImage ResizerChange the pixel size of a picture without leaving the page — fit it in a box, cover one, or scale it by a percentage.
- DevelopersXML FormatterIndents XML so the structure is visible, or strips the whitespace back out again.
- DevelopersHTML MinifierCollapses whitespace and removes comments, leaving pre and script blocks alone.
- DevelopersImage CompressorSqueeze a photo down to a smaller file at the same pixel size, and see exactly how many bytes you saved.
- DevelopersJavaScript MinifierRemoves comments and spare whitespace from JavaScript, conservatively.
- DevelopersExcel to CSV Converter (XLSX)Turn any sheet of an Excel .xlsx workbook into a CSV file, with dates written as dates and the separator you choose, in your browser.
- DevelopersCSV to Excel Converter (XLSX)Turn a CSV or TSV file into a real Excel .xlsx workbook, with numbers stored as numbers and text kept as text, in your browser.
- DevelopersHash GeneratorThe SHA-256, SHA-512, SHA-1 or MD5 hash of any text, in hex, capitals and Base64, worked out in your browser.
- DevelopersXML ValidatorChecks that an XML document is well formed and says which tag broke it.
- DevelopersImage ConverterTurn a picture into PNG, JPEG or WebP in your browser, and see what the change does to the file size.
- DevelopersJSON to Excel Converter (XLSX)Turn a JSON list of records, such as an API response or an export, into an Excel .xlsx sheet with one column per field, in your browser.
- DevelopersText to Binary Converter (and Hex, Decimal)Turn text into the bytes a computer stores, written in binary, hexadecimal, decimal or octal, and turn bytes back into text.
- DevelopersImage to PDF ConverterPut a picture on an A4 or Letter page and save it as a PDF, with the margin and orientation you choose.
- DevelopersPNG to WebP ConverterTurn a PNG into a much smaller WebP that keeps its transparent background, in your browser, with nothing uploaded.
- DevelopersXML to JSON ConverterConvert an XML document, RSS feed, GPX track or any XML file into JSON, with attributes, repeated elements and text mapped the usual way.
- DevelopersYAML to JSON ConverterConvert YAML from Docker Compose, Kubernetes, GitHub Actions or any config file into JSON, with clear error messages that give the line number.
- DevelopersCSS Gradient GeneratorBuild a linear, radial or conic gradient and get the CSS line, with the contrast between the two ends.
- DevelopersWebP to PNG ConverterSave a WebP image as a PNG, transparency included, so it opens in any editor, document or older app.
- DevelopersImage CropperKeep a rectangle of a picture and throw the rest away, with the exact pixel numbers rather than a rough drag.
- DevelopersJPG to WebP ConverterConvert JPEG photos to WebP, usually 25 to 35 % smaller at the same visual quality, in your browser.
- DevelopersJSON to YAML ConverterConvert JSON into clean, readable YAML for Kubernetes, Docker Compose, GitHub Actions or any configuration file.
- DevelopersPassphrase GeneratorA password made of random common words, with the exact entropy stated so you can judge it rather than trust it.
- DevelopersSVG to PNG ConverterTurn an SVG drawing into a PNG at 1×, 2×, 4× or 8× its size, keeping the transparent background, in your browser.
- DevelopersBox Shadow GeneratorBuild a CSS box shadow or text shadow from the offsets, blur, spread and colour, and see how much room it needs.
- DevelopersPNG to ICO Converter (Favicon Maker)Turn a PNG, JPG, WebP or SVG into a .ico file with several sizes inside, ready to use as a favicon or a Windows icon.
- DevelopersPNG to JPG ConverterSave a PNG as a JPEG at the quality you choose, and see how many bytes that costs or saves.
- DevelopersRandom Token GeneratorRandom strings in hex, Base58, Base64 or digits, with the exact number of bits of entropy they carry.
- DevelopersURL Slug GeneratorTurn titles into clean, readable web addresses: lowercase, accents removed, words joined by hyphens, one slug per line.
- DevelopersVideo Bitrate CalculatorBitrate from resolution, frame rate and bits per pixel, with the file size, the raw uncompressed rate and the compression ratio.
- DevelopersScreen Resolution CheckerThe size of the screen you are on, in the pixels pages are told about and in the pixels the panel really has.
- DevelopersBase64 to Image ConverterPaste Base64 text or a data URI and see the picture, find out what kind of file it really is, and save it with the right extension.
- DevelopersBorder Radius GeneratorSet four corners and get the shortest CSS that produces them, with a warning when the box is too small to hold them.
- DevelopersImage to Base64 Converter (Data URI)Turn an image into Base64 text you can paste straight into HTML, CSS or JSON, as a data URI, an <img> tag or a CSS background.
- DevelopersJPG to PNG ConverterSave a JPEG photograph as a PNG file, in your browser, without sending it anywhere.
- DevelopersHTML PreviewPaste HTML and see it drawn straight away, with a count of the elements and a list of any tags left open.
- DevelopersAudio File Size CalculatorHow much space uncompressed audio takes, from the sample rate, bit depth, channels and length — and how much a compressed version would take.
- DevelopersBrowser CheckerWhat browser you are using, which version, which engine and which system — read from the line your browser announces.
- DevelopersSRT to VTT Converter (Subtitles)Convert SubRip (.srt) subtitles into WebVTT (.vtt) for HTML5 video and most web players, with an optional time shift.
- DevelopersStreaming Bandwidth CalculatorPeak bandwidth for a number of concurrent viewers, and the monthly data transfer and cost that follow from it.
- DevelopersWebP to JPG ConverterTurn a WebP picture into an ordinary JPEG that any program will open.
- DevelopersVTT to SRT Converter (Subtitles)Convert WebVTT (.vtt) subtitles into SubRip (.srt) for VLC, video editors, TVs and media players, with an optional time shift.
- DevelopersDevice CheckerWhat your browser is willing to say about the machine underneath: platform, processor cores, memory and touch.
- DevelopersAudio Latency CalculatorBuffer latency in milliseconds, round-trip delay, and the distance you would have to stand back to feel the same thing.
- DevelopersPX to REM Converter (CSS Units)Convert a CSS pixel size to rem, em, points, percent and viewport units, for any root font size.
- DevelopersColour Depth CalculatorLevels per channel, total colours, raw bitrate and the size of one banding step, for any bit depth.
- DevelopersFFT Resolution CalculatorFrequency bin width, window length, usable bins and hop size, from the sample rate and the FFT size.
- DevelopersChroma Subsampling CalculatorData rate and frame size for 4:4:4, 4:2:2, 4:2:0 and 4:1:1, with the chroma resolution and what each one saves.
- DevelopersEthernet Goodput Calculator (Real Throughput and Frames per Second)The real data rate you can expect on an Ethernet link once preamble, headers, checksum, inter-frame gap and IP/TCP headers are paid for, and how many frames per second the line carries.
- DevelopersPixel Density (PPI) CalculatorPixels per inch of a screen from its resolution and diagonal, the size of each pixel, and the viewing distance beyond which individual pixels disappear.
- DevelopersSLA Uptime and Downtime CalculatorHow much downtime an availability target such as 99.9 % allows per year, month, week and day.
- DevelopersGOP and Keyframe Interval CalculatorGOP duration in seconds, keyframes per minute, the I, P and B counts inside a GOP, and whether it lines up with the segment length.
- DevelopersAmdahl's Law Calculator (Parallel Speed-up Limit)Speed-up of a program on n processors from the share that can run in parallel, the ceiling it can never pass, and how efficiently the cores are used.
- DevelopersBloom Filter Calculator (Size, Hash Functions, False-Positive Rate)How many bits, how much memory and how many hash functions a Bloom filter needs to hold a number of items at a false-positive rate you accept.
- DevelopersCCTV Storage Calculator (NVR / DVR)How many terabytes a video surveillance recorder needs for a number of cameras, a bitrate and a retention period.
- DevelopersCOCOMO Software Effort Estimator (Basic COCOMO)Effort in person-months, development time, average team size, productivity and cost of a software project from its size in thousands of lines of code, using Boehm's Basic COCOMO.
- DevelopersFloating-Point Precision Calculator (IEEE 754 Float, Double, Half, bfloat16)How coarse the number line is around any value in half, bfloat16, single or double precision: the gap to the next number, machine epsilon, reliable digits and the largest integer that is still exact.
- DevelopersHalstead Complexity Metrics Calculator (Volume, Difficulty, Effort)Halstead volume, difficulty, effort, estimated writing time and delivered bugs of a program from its counts of operators and operands.
- DevelopersMaintainability Index Calculator (Halstead, Cyclomatic Complexity, Lines of Code)The maintainability index of a function, class or file from its Halstead volume, cyclomatic complexity and lines of code, on the original scale and on the 0–100 scale used by Visual Studio.
- DevelopersRAID Capacity CalculatorUsable space, storage efficiency and how many disks can fail for RAID 0, 1, 5, 6 and 10, with the capacity your computer will actually report.
- DevelopersRAID IOPS Calculator (Write Penalty)Random IOPS an array can sustain for a given mix of reads and writes, after the RAID write penalty, and the throughput that represents.
- DevelopersTCP Throughput Calculator (Mathis Formula: Loss and Round-Trip Time)The most one standard TCP connection can carry for a given round-trip time, segment size and packet loss rate — and the loss rate you would need for a target speed.
- DevelopersTimer and PWM Frequency Calculator (Prescaler, TOP and Resolution for Arduino, AVR, STM32)PWM or overflow frequency from the timer clock, prescaler and counter top value, with the period, the duty-cycle resolution and the TOP you would need for a wanted frequency.
- DevelopersUniversal Scalability Law Calculator (Gunther, Amdahl and Beyond)Relative capacity and throughput of a system with N processors or nodes, from its contention and coherency coefficients, with the number of nodes at which adding more starts to hurt.
- DevelopersVoIP Bandwidth Calculator (Codec, Packet Size and Headers)Real network bandwidth of a voice call from the codec bit rate, packet interval, IP version and link layer, and the total for several calls — in each direction.
- DevelopersFibre Latency Calculator (Minimum Ping by Distance)The physical minimum round-trip time over an optical fibre route, from its length, compared with light in vacuum.
- DevelopersCache Latency Calculator (Average Memory Access Time)Average access time of a cache or any fast-store-in-front-of-a-slow-one from the hit rate, hit time and miss penalty, and the speed-up it gives.
- DevelopersError Budget and Burn Rate Calculator (SLO)Error budget, burn rate and time until the budget runs out, from an SLO, the error rate you are seeing and the SLO window.
- DevelopersHash Table Load Factor Calculator (Expected Probes: Linear Probing, Double Hashing, Chaining)The load factor of a hash table and the average number of probes a lookup needs — for linear probing, double hashing and chaining — plus the table size that keeps you under a chosen load.
- DevelopersBandwidth-Delay Product Calculator (TCP Window)How much data must be in flight to fill a network link, and the throughput a single TCP connection can reach with a given window size.
- DevelopersID Collision Probability Calculator (UUID, Random Tokens)Chance that two randomly generated identifiers — UUIDs, tokens, short codes — come out the same, and how many you can make before that becomes likely.
- DevelopersGustafson's Law Calculator (Scaled Speedup)Speedup when the problem grows with the number of processors, by Gustafson's law, set beside Amdahl's fixed-size speedup.
- DevelopersPUE Calculator (Data Centre Energy Efficiency)Power usage effectiveness and DCiE of a data centre or server room, with how much power and energy go to cooling and losses instead of computing.
Everyday
Tips, discounts, splitting bills, cooking measures, travel and the small calculations that come up every week.
- EverydayTip CalculatorTip amount, total bill and the share per person, all at once.
- EverydayRandom PickerPicks one or several entries at random from a list you paste in, with a seed you can publish.
- EverydayUnit Price ComparisonCompare two package sizes by price per 1000 units of quantity.
- EverydayFeet and Inches to CentimetresConvert a height in feet and inches to centimetres, or back again.
- EverydayCooking Measurement ConverterConvert cooking volumes into grams and ounces for common ingredients.
- EverydayCoin FlipFlips one coin or a thousand, with the count of heads and tails and the longest run.
- EverydayDice RollerRolls any number of dice with any number of sides, with a modifier, total, highest and lowest.
- EverydayLottery Number GeneratorDraws a line of lottery numbers for any format, and shows how many combinations exist.
- EverydayRandom WheelSpins a list and gives you a winner, a runner-up and the full running order.
- EverydaySplit the Bill CalculatorEqual share per person, with a rounded-up amount and the small surplus it creates.
- EverydayShoe Size ConverterEuropean, UK, US and Mondopoint shoe sizes from the length of the foot in centimetres.
- EverydayTeam GeneratorSplits a list of names into balanced teams at random, with the seed recorded.
- EverydayFancy Text Generator (Bold, Italic and Script Unicode Letters)Write your text in bold, italic, script, gothic, double-struck or monospace Unicode letters that you can paste where formatting is not allowed, such as Instagram, LinkedIn or X.
- EverydayOven Temperature ConverterCelsius, Fahrenheit, gas mark and the fan-oven equivalent, all at once.
- EverydayNumber to Words Converter (English, Portuguese, Spanish, French)Write any number or amount of money in words, in English, European Portuguese, Spanish or French, for cheques, invoices and contracts.
- EverydayRecipe ScalerRescale any ingredient quantity from one number of servings to another.
- EverydayEgg Boiling Time CalculatorHow long to boil an egg for a chosen yolk temperature, from its weight and starting temperature.
- EverydayPros and Cons CalculatorA for-and-against list where each reason carries the weight you give it, so the answer reflects what matters and not just how many things you thought of.
- EverydayHeat Pump Running Cost CalculatorAnnual heating cost of a heat pump against a gas boiler, with the SCOP needed to break even.
- EverydayWeighted Decision MakerLet chance choose between your options, but give the ones you lean towards a better chance of coming up.
- EverydayDefrosting Time CalculatorHow long frozen food takes to thaw in the fridge or in cold water, with the number of water changes needed.
- EverydayAir Conditioner Size CalculatorAdd up the heat a room gains and turn it into watts and BTU per hour, so you can match a unit to the room rather than guess.
- EverydayCat Age Calculator (Cat Years to Human Years)Your cat's age in human years, using the veterinary life-stage chart, and which life stage it is in.
- EverydayReading Time CalculatorHow long a text takes to read silently, to read aloud, and how many pages it fills.
- EverydayBingo Card GeneratorA standard 75-ball bingo card, five by five, with the free centre square.
- EverydayHousehold Water Usage CalculatorAdd up what your home actually uses — showers, flushes, washing, everything else — in litres a day and money a month.
- EverydayAir Fryer Conversion CalculatorAir fryer temperature and time from an oven recipe, with the point to shake or turn the food.
- EverydayCoffee to Water Ratio CalculatorGrams of coffee for a volume of water, and how much brewed coffee you actually end up with.
- EverydayMorse Code TranslatorTranslate text into Morse code and Morse back into text, using the international ITU table, with letters, digits and punctuation.
- EverydayScreen Size CalculatorActual width and height of a screen from its diagonal and aspect ratio.
- EverydaySous Vide Time Calculator (Cooking Time by Thickness)How long a steak, fillet, sausage or meatball needs in a water bath before its centre reaches the temperature you want, from its thickness and starting temperature.
- EverydayRandom Card GeneratorDraws cards from a shuffled 52-card deck, without ever repeating one.
- EverydayDog Age CalculatorA dog's age in human-equivalent years by the epigenetic formula, with the old seven-year rule for comparison.
- EverydayRaised Bed Soil CalculatorLitres of soil or compost needed to fill a raised bed or planter, with the number of bags and the cost.
- EverydayTV Viewing Distance CalculatorIdeal seating distance for a screen size, based on the horizontal angle it fills.
- EverydayAlcohol Units CalculatorGrams of pure alcohol in a drink, in UK units, US standard drinks and calories.
- EverydayBread Hydration CalculatorWater, salt and starter weights for a given flour weight, using baker's percentages.
- EverydayBaggage Allowance CalculatorHow far over the weight limit your case is, what the excess will cost across all your bags, and whether it is within the size rule.
- EverydayPizza Value CalculatorWhich pizza gives more area for the money, and by how much.
- EverydayRoast Cooking Time CalculatorOven time for a joint from its weight, plus resting time and the finish time in hours and minutes.
- EverydayShower Cost CalculatorCost and energy of one shower, the water used, and the yearly cost for a household.
- EverydaySubscription Cost CalculatorYearly and monthly total of your subscriptions, what share of income they take and what five years costs.
- EverydayBicycle Spoke Length Calculator (Wheel Building)Length of the spokes for a wheel you are building, from the rim's effective diameter, the hub flange, the spoke count and the lacing pattern.
- EverydayDilution Ratio CalculatorConcentrate and water needed for a final volume at a given dilution ratio.
- EverydayElo Rating Calculator (Chess and Game Rating Change)Your expected score against an opponent, and your new rating after a win, draw or loss, using the Elo system with a K-factor of your choice.
- EverydayRandom Emoji GeneratorDraws random emoji from a chosen category, or from all of them at once.
- EverydayEpoxy Resin Calculator (How Much Resin for a Pour)Millilitres of mixed epoxy, split into resin and hardener, for a table, tray, coaster or mould of a given size and depth, with a margin for waste.
- EverydayParty Food Quantity CalculatorHow much main course, sides and bread to buy for a number of guests, with a margin.
- EverydayPhone Charging Time CalculatorTime to charge a phone from its current level, with the battery's energy in watt-hours.
- EverydayPlant Spacing CalculatorHow many plants fit a plot at a given spacing, in rows and in total, with the density per square metre.
- EverydayTobler's Hiking Function Calculator (Walking Speed on Slopes)Walking speed and time for a stretch of path from its gradient, using Tobler's hiking function, which makes you fastest on a gentle downhill, with a correction for off-path ground.
- EverydayBaking Pan Conversion CalculatorFactor to scale a recipe when your tin is a different size or shape from the one in the book.
- EverydayWill This Bed Fit CalculatorHow much floor is left on each side and at the foot once a given bed is in a given room, and the widest bed the room takes.
- EverydayBike Saddle Height Calculator (LeMond and Hamley–Thomas Methods)A starting saddle height for your bike from your inseam, by the LeMond and the Hamley–Thomas formulas, measured from the pedal axis and from the bottom bracket.
- EverydayParty Drinks CalculatorDrinks, wine bottles, soft drinks, ice and glasses for a party of a given size and length.
- EverydaySafe Listening Time Calculator (Noise Exposure, NIOSH and OSHA)How long you can listen or work at a sound level each day before reaching the noise exposure limit, and what dose your day adds up to.
- EverydayWashing Machine Cost CalculatorCost of one wash cycle and of a year of washing, with the electricity and water it uses.
- EverydayMobile Data Usage CalculatorMonthly data use from video, music and browsing hours, with the share video takes.
- EverydayPool Chlorine Dose CalculatorProduct needed to raise pool chlorine to a target level, in grams and kilograms, with the pure chlorine equivalent.
- EverydayPet Food Portion CalculatorDaily and per-meal food quantity for a dog or cat, from its weight and activity level.
- EverydayPhoto Print Size and DPI CalculatorPrint size at a chosen resolution, and the resolution you would get at 30 cm wide.
- EverydayDepth of Field CalculatorNear and far limits of sharpness, the total depth of field and the hyperfocal distance.
- EverydayRing Size CalculatorInner diameter of a ring from the finger circumference, in millimetres, centimetres and inches.
- EverydayWater Tank Fill Time CalculatorTime to fill a tank from its current level at a given flow rate.
- EverydayWind Chill CalculatorHow cold the air feels on exposed skin once the wind is taken into account.
- EverydayBaseball Batting Stats Calculator (AVG, OBP, SLG, OPS)Batting average, on-base percentage, slugging, OPS, isolated power and total bases from a hitter's counting stats.
- EverydayCandle Wax Calculator (Wax and Fragrance Oil per Container)Grams of wax and fragrance oil to pour a container candle, and the total for a batch, from the capacity of the jar, how full it is poured and the fragrance load.
- EverydayGolf Handicap Calculator (World Handicap System Differential and Course Handicap)The score differential of a round and the course handicap for a tee, using the World Handicap System formulas with the course rating and slope.
- EverydayPicture Hanging CalculatorEven spacing for a row of pictures and the nail height for eye-level hanging.
- EverydayPower Bank Charges CalculatorHow many times a power bank can really charge your phone, its energy in watt-hours and whether you can take it on a plane.
- EverydayProjector Throw Distance CalculatorHow far the projector must be from the screen for a given image size and throw ratio, and the largest picture your room allows.
- EverydaySourdough Starter Feeding CalculatorFlour and water to feed a starter at a chosen ratio, how much you end up with, and how much to keep back.
- EverydayStandby Power Cost CalculatorYearly cost and energy of devices left on standby, per device and in total, with the carbon behind it.
- EverydayTide Height Calculator (Rule of Twelfths)Height of the water at any time between low and high tide, by the rule of twelfths and by a sine curve, from the two tide heights and the time elapsed.
- EverydayWater Heating Time Calculator (Boiler, Kettle, Tank)How long an electric water heater, kettle or immersion heater takes to bring water to temperature, the energy it uses and what it costs.
- EverydayAquarium Water Change CalculatorUsable litres in a tank and the volume of a partial water change, with the dose of conditioner needed.
- EverydayGarden Watering CalculatorLitres a garden needs each week, how long to run the hose, and what it costs over a year.
- EverydayMoving Boxes CalculatorRough number of packing boxes for a house move, split by box size.
- EverydayMusical Note Frequency CalculatorFrequency of a note a number of semitones from A4, with its MIDI number, wavelength and the octave above.
- EverydayBicycle Gear CalculatorDevelopment, gear ratio, gear inches and road speed for a chainring and sprocket combination.
- EverydayBrine Salt CalculatorSalt needed for a brine at a chosen strength, in grams and tablespoons, with the strength counting the food as well.
- EverydayExposure Value CalculatorExposure value from aperture, shutter and ISO, with the EV at ISO 100 and the light level it corresponds to.
- EverydayFirewood Stack Volume CalculatorStacked volume of a woodpile and the solid wood it actually contains.
- EverydayNFL Passer Rating Calculator (QB Rating)The official NFL passer rating, from 0 to 158.3, plus the NCAA passing efficiency, completion percentage and yards per attempt.
- EverydayField of View CalculatorHorizontal, vertical and diagonal angles of view, the frame size at a distance, and the crop factor.
- EverydayGrass Seed CalculatorSeed needed for a new lawn, bags and cost, with the lighter rate for overseeding an existing one.
- EverydayPrinting Cost Per Page CalculatorCost of a printed page including paper, with the monthly and yearly total and when the cartridge runs out.
- EverydayCricket Run Rate Calculator (Current and Required)Current run rate, required run rate, runs and balls left and the projected total for a limited-overs innings.
- EverydayLawn Fertiliser CalculatorHow much product to spread for a target nitrogen dose, the rate per square metre, bags needed and cost.
- EverydayTempo to Delay Time CalculatorDelay times in milliseconds for a tempo, from quarter notes down to sixteenths, with dotted and triplet values.
- EverydayABV Calculator for Homebrew (Beer, Wine, Cider)Alcohol content of a home-brewed beer, wine or cider from its original and final gravity readings, with the attenuation and original extract.
- EverydayHorse Weight Calculator (Girth and Length)Estimated weight of an adult horse from heart girth and body length, by the formula used by agricultural extension services, plus a daily forage figure.
- EverydayDripping Tap Water Loss Calculator (What a Leak Costs)Litres a dripping tap or running toilet wastes per day, month and year, and what that costs at your water price.
- EverydayPanorama Shots Calculator (How Many Photos and How Far to Turn)How many photos to take for a panorama of a given width, how far to turn the camera between shots, and the overlap you end up with, from lens, sensor and overlap.
- EverydaySailboat Hull Speed Calculator (Displacement-Length and Sail Area Ratios)The speed a displacement sailboat struggles to exceed, from its waterline length, plus the two classic ratios that tell a light, fast boat from a heavy, slow one.
- EverydayBaseball ERA and WHIP CalculatorEarned run average, WHIP, strikeouts and walks per nine innings and strikeout-to-walk ratio from a pitcher's line.
- EverydayBasketball True Shooting Percentage Calculator (TS% and eFG%)True shooting percentage, effective field goal percentage, plain field goal percentage and points per shooting attempt from a player's box score.
- EverydayBeer IBU Calculator (Tinseth Formula)Bitterness in International Bitterness Units from two hop additions, by Glenn Tinseth's formula, with the utilisation and the BU:GU balance.
- EverydayCurtain Fabric CalculatorHow much fabric a pair of curtains needs, counted in whole fabric widths.
- EverydayCompost C:N Ratio CalculatorThe carbon to nitrogen ratio of a compost mix from the weights and analyses of two materials.
- EverydayHow Many Boxes Fit in a Space Calculator (Van, Boot, Shelf, Pallet)How many identical boxes fit in a van, car boot, cupboard, shelf or pallet, trying every way of turning them, with how full the space ends up and the total weight.
- EverydayGas Meter Reading to kWh Calculator (m³ or 100 ft³ to Energy)The kWh and the cost of the gas you used between two meter readings, from the volume on the meter, the calorific value on your bill and the correction factor.
- EverydayHeating Fuel Cost Comparison Calculator (Pellets, Oil, Gas, Wood, Electricity)The true cost of one kWh of heat from two fuels sold in different units, the yearly bill for each, the saving and the price at which they would break even.
- EverydayND Filter Exposure Calculator (Long Exposure)Shutter speed with a neutral density filter from the speed without it and the filter's strength in stops, with the ND factor and optical density.
- EverydayPassport Validity Checker (3-Month and 6-Month Rule for Travel)Whether your passport has enough validity left for a trip, given its expiry date, the day you leave the destination and the validity the country requires.
- EverydayPizza Dough Calculator (Flour, Water, Salt and Yeast for Any Number of Pizzas)Grams of flour, water, salt and yeast for a number of pizzas of a chosen size, using baker's percentages, with the weight of each dough ball.
- EverydayPythagorean Expectation Calculator (Expected Wins)The winning percentage and number of wins a team 'should' have from the runs or points it scored and allowed, and how many it gained or lost to luck.
- EverydayString Tension Calculator (Guitar and Plain Strings)Tension of a plain string tuned to a given note on a given scale length, in newtons, kilograms-force and pounds, with how it changes around the note.
- EverydayBowling Handicap CalculatorYour ten-pin bowling handicap per game and per series from the league's basis and percentage and your average, plus the game score with handicap.
- EverydayBeer Colour Calculator (SRM and EBC, Morey Equation)Colour of a beer in SRM and EBC from the weight and colour of up to three malts and the batch volume, by Morey's equation.
- EverydayAlcohol Proof Converter (ABV, US Proof, UK Proof)Convert alcohol by volume to US proof and British proof, or either proof back to ABV, with how far over or under proof a spirit is on the old UK scale.
- EverydayAquarium Volume and Weight Calculator (Litres, Gallons and Full Weight)How much water an aquarium really holds once the glass and the gap at the top are taken out, and how much the full tank weighs with glass, substrate and decor.
- EverydayBass Reflex Port Length CalculatorLength of the port tube that tunes a bass-reflex loudspeaker box to a chosen frequency, from the box volume and the port diameter.
- EverydayCircle Skirt Calculator (Waist Radius and Fabric)Radius of the waist cut-out and the fabric you need for a full, half or quarter circle skirt from your waist measurement and the length you want.
- EverydayCocktail ABV Calculator (Strength of a Mixed Drink)The alcohol percentage of a cocktail or mixed drink from up to four ingredients and the water that ice adds, with the pure alcohol it holds and the UK units.
- EverydayCoffee Extraction Yield Calculator (TDS)Share of the ground coffee that ended up dissolved in your cup, from the dose, the brewed weight and a refractometer TDS reading.
- EverydayCrowd Size Calculator (People per Square Metre)How many people fit in, or were at, a square, hall or field from its area and how packed the crowd is.
- EverydayDrone Flight Time Calculator (From Battery and Power Draw)Estimated flight time of a drone from its battery capacity and voltage, the share of it you use and the average power it draws, plus the distance at a given speed.
- Everyday3D Printer Filament Length Calculator (Metres From Grams)Length of filament in a spool from its weight, material and diameter, plus the weight and cost of each metre.
- EverydayHelium Balloon Lift Calculator (How Many Balloons to Lift a Load)The lifting power of helium per litre at your temperature and pressure, the lift of one balloon after its own weight, and how many balloons it takes to lift a given mass.
- EverydayHot Water Wait Time Calculator (Pipe Length and Water Wasted)How long you wait for hot water at the tap and how much water goes down the drain meanwhile, from the pipe's bore and length and the tap's flow.
- EverydayKnitting Gauge Calculator (Stitches and Rows for Your Tension)How many stitches to cast on and rows to knit for a given size from your own gauge, and how to adapt a pattern written for a different gauge.
- EverydayPower from Electricity Meter Pulses Calculator (LED Blinks or Disc Turns)The power in watts that an appliance or a whole home is drawing, from the blinks of the meter's LED or the turns of its disc, with the yearly energy and cost that implies.
- EverydayMicrowave Time Converter (Adjust for Your Wattage)Convert a cooking time written for one microwave power to the time for yours, in total seconds and in minutes and seconds.
- EverydayPet Food Bag Duration Calculator (How Long a Bag of Kibble Lasts)How many days a bag of dry food lasts for one or more pets, and what that costs per day, per month and per year, from the bag size and the daily ration.
- EverydayPicture Frame Mat Calculator (Window Size and Border Widths)The size to cut the window of a picture mat, and the widths of the side, top and bottom borders, from the frame opening, the picture size and how much the mat overlaps it.
- EverydayPond Liner Calculator (Liner Size and Volume of a Garden Pond)The size of liner to buy for a garden pond from its length, width and depth, with the underlay area, the surface and a volume estimate.
- EverydaySulphite (SO₂) Addition Calculator for Wine, Cider and MeadGrams of potassium metabisulphite to add to reach a target free SO₂ in a given volume, after allowing for the free SO₂ already present.
- EverydaySpeaker SPL Calculator (Loudness from Sensitivity, Power and Distance)Sound level in dB at the listening position from the speaker's sensitivity, the power, the distance and the number of speakers — or the power needed for a level you want.
- EverydayTime-Lapse Calculator (Interval, Photos and Storage)The interval to set on your camera, the number of photos and the storage you need for a time-lapse of a given event length and finished clip.
- EverydayYeast Converter (Fresh, Active Dry and Instant)Convert between fresh, active dry and instant yeast in a recipe, using the common baking ratio of about 1 : 0.4 : 0.33.
- EverydayHockey Goalie Stats Calculator (SV%, GAA, GSAA)Save percentage, goals-against average and goals saved above average for an ice hockey goaltender.
- EverydayAquarium CO₂ Calculator (CO₂ ppm from pH and KH)The dissolved CO₂ in a planted aquarium from its pH and carbonate hardness, and the pH you would need to hold for a target CO₂ level.
- EverydayBrix to Specific Gravity ConverterSpecific gravity and dissolved sugar of a juice, must or wort from a refractometer reading in degrees Brix.
- EverydayEven Increases and Decreases Calculator (Knitting and Crochet)How to space a number of increases or decreases evenly across a row or round: the plain stitches between them, and how many gaps are one stitch longer.
- EverydayFlash Guide Number Calculator (Distance and Aperture)How far a flash reaches at a given aperture and ISO, or the aperture to use for a subject at a given distance, from its guide number.
- EverydayFood Drying Yield Calculator (Dehydrator: Dried Weight from Fresh)How much a batch weighs once dried, how much water has to go, the share of the weight that remains, and how much fresh food makes a given amount of dried.
- EverydayFret Position Calculator (Guitar and Bass Fret Spacing)Distance from the nut to any fret of a guitar, bass, ukulele or banjo from its scale length, and the gap to the previous fret.
- EverydayGrowing Degree Days Calculator (GDD for Crops, Garden and Insects)The growing degree days a day adds, how many days of that weather a crop stage needs, and the total after a run of such days.
- EverydayLawn Mowing Time Calculator (How Long to Cut the Grass)How long a lawn takes to mow, how far you walk, the area you get through per hour and the hours a season costs, from the lawn's area, the mower's width and your pace.
- EverydayPearson Square Calculator (Mixing Two Strengths)How much of a strong and a weak ingredient to mix to reach a target strength: the parts of each, and the amounts for a total quantity.
- EverydayPool Salt Calculator (Kilos of Salt for a Saltwater Pool)Kilograms of salt to add to a swimming pool to go from its current salt level to the one your chlorinator needs, and how many bags that is.
- EverydayQuilt Backing and Binding Calculator (Fabric Needed)How much fabric the backing and the binding of a quilt need, how many pieces of backing to join, and how many binding strips to cut, from the size of the quilt top.
- EverydaySpeaker Delay Calculator (Delay Towers and Fill Speakers)The delay to give a closer fill or delay speaker so its sound arrives together with the main speakers, from the two distances and the air temperature.
- EverydayFrame Rate and Frame Count CalculatorFrames in a clip, how long one frame lasts, and what happens when you change the rate.
Automotive
Fuel consumption, trip cost, speed and distance, engine figures and tyre or wheel calculations.
- AutomotiveFuel Consumption CalculatorReal consumption from a tankful, in L/100 km, km/L and both kinds of mpg.
- AutomotiveTrip Cost CalculatorWhat a journey really costs: fuel, tolls and parking, with the total split per person and per kilometre.
- AutomotiveEV Charging Cost CalculatorCost of a charge, energy drawn from the socket, range added and cost per kilometre.
- AutomotiveFuel Cost Comparison CalculatorCompare two cars on what they cost per 100 km, whatever they run on, and see how far you drive before a higher purchase price pays for itself.
- AutomotiveTyre Size CalculatorOverall diameter, rolling circumference and sidewall height from a tyre code.
- AutomotiveEV Range CalculatorHow far an electric car actually goes once you take off the unusable part of the battery, the reserve you keep and the cold or the motorway.
- AutomotiveBraking Distance CalculatorStopping distance split into reaction distance and braking distance, plus the total time.
- AutomotiveFuel Savings CalculatorYearly fuel and money saved by switching to a car with lower consumption.
- AutomotiveCar Lease CalculatorWork a lease payment out from the price, the residual value and the rate, and see how much of it is the car losing value and how much is interest.
- AutomotiveAnnual Car Cost CalculatorTotal yearly cost of running a car, per month and per kilometre.
- AutomotiveCarpool Cost CalculatorFair share per passenger for fuel and tolls on a shared journey.
- AutomotiveTwo-Stroke Fuel Mix Calculator (Petrol and Oil Ratio)Millilitres of two-stroke oil to add to a given amount of petrol for a 50:1, 40:1 or any other ratio, and the ratio you really have if you already added the oil.
- AutomotiveMileage Allowance CalculatorYearly mileage reimbursement, what the fuel alone costs, and the margin between the two.
- AutomotivePower-to-Weight Ratio CalculatorPower per tonne and kilograms per horsepower, including passengers and luggage.
- AutomotiveEngine Displacement CalculatorEngine capacity in cubic centimetres and litres from bore, stroke and cylinder count.
- AutomotiveCar CO₂ Emissions Calculator (L/100 km to g/km and Yearly CO₂)Grams of CO₂ per kilometre from fuel consumption, the CO₂ of a year's driving, and the consumption that a CO₂ figure on a car label implies.
- AutomotiveGear Speed CalculatorRoad speed at a given engine speed in a chosen gear, plus the wheel speed and overall ratio.
- AutomotiveCompression Ratio CalculatorStatic compression ratio from bore, stroke and combustion chamber volume, with the swept volume.
- AutomotiveSpeedometer Error from Tyre SizeHow much a change of tyre size shifts the indicated speed and the odometer reading.
- AutomotiveTyre Pressure Temperature CalculatorHow tyre pressure changes with temperature, in bar, psi and as a percentage.
- AutomotiveTrailer Tongue Weight CalculatorDownload on the towball for a loaded trailer, against the limit of your towbar.
- AutomotiveDyno Correction Factor Calculator (DIN 70020 and SAE J1349)The factor that converts power measured on a dyno on the day to standard atmospheric conditions, by DIN 70020 or SAE J1349, and the corrected power.
- AutomotiveEngine Airflow Calculator (CFM for Carburettor, Throttle Body or Turbo Sizing)How much air a four-stroke engine swallows at a given speed, in CFM, litres per second and grams per second, from its displacement, volumetric efficiency and boost.
- AutomotiveWheel Offset and Backspacing CalculatorBackspacing from wheel width and ET offset, and the change when swapping to a different offset.
- AutomotiveAir-Fuel Ratio to Lambda Converter (Petrol, Diesel, E85, Ethanol, LPG)Convert an air-fuel ratio to lambda (λ) and back for the fuel you burn, with the equivalence ratio and how far the mixture is from ideal.
- AutomotiveAltitude Power Loss Calculator (Naturally Aspirated Engines)How much power a naturally aspirated engine loses at altitude and in warm air, from the standard atmosphere and your air temperature.
- AutomotiveApparent Wind Calculator (Sailing and Cycling)The wind you actually feel on a moving boat or bike — its speed and the angle it comes from — given the true wind and your own speed.
- AutomotiveBraking Weight Transfer Calculator (Axle Loads When Braking, Stoppie and Wheelie Limits)Load on the front and rear axles under hard braking, from the weight, wheelbase, height of the centre of gravity and how hard you brake — plus the point where the rear wheels would lift.
- AutomotiveSpeeding Time Saved Calculator (How Much Time Does Driving Faster Save?)Minutes saved on a trip by driving at a higher speed, and the average speed you would need to arrive a given number of minutes earlier.
- AutomotiveWheel Torque Calculator (Gearing, Tractive Force and Road Speed)Torque at the wheels, the pushing force at the road and the road speed at a given engine speed, from the engine torque, the gear and final-drive ratios and the tyre radius.
- AutomotiveWind Correction Angle Calculator (Wind Triangle: Heading and Ground Speed)The heading to fly or steer to hold a desired course in a crosswind, the drift correction angle and the resulting ground speed.
- AutomotiveAircraft Weight and Balance Calculator (Centre of Gravity of a Light Aircraft)Total weight and centre of gravity of a light aircraft loaded with people, baggage and fuel, checked against your weight and CG limits.
- AutomotiveAnchor Scope Calculator (How Much Chain and Rope to Let Out)Length of anchor rode to let out for a given depth, tide and scope ratio, with the horizontal reach of the rode and the radius of the circle your boat can swing through.
- AutomotiveBank Angle, Load Factor and Stall Speed in a Turn CalculatorLoad factor, raised stall speed, turn radius and rate of turn for an aircraft in a banked level turn, plus the bank angle that gives a standard-rate turn.
- AutomotiveBike Chain Wear Calculator (Chain Stretch Percentage)How worn a bicycle chain is, from the measured length of a number of links, with the length at which common wear limits are reached.
- AutomotiveCPA and TCPA Calculator (Closest Point of Approach Between Two Vessels)How close another vessel will pass and how many minutes until then, from its bearing, range, course and speed and your own — the numbers a radar or AIS shows.
- AutomotiveEthanol Fuel Blend Calculator (E10 + E85 Mix, Flex-Fuel)Ethanol content of a tank after topping up with a different blend, and how much E85 (or E10) to add to land on the percentage you want.
- AutomotiveGear Shift RPM Drop Calculator (Where the Revs Land After an Upshift)Engine speed just after you change up (or down) a gear, how much the revs fall, and the road speed at which it happens, from the two gear ratios.
- AutomotiveGlide Distance Calculator (How Far Can I Glide After an Engine Failure?)How far an aircraft, glider or paraglider can glide from a given height, from its glide ratio, with the effect of headwind or tailwind and the time in the air.
- AutomotiveHydroplaning Speed Calculator (Aquaplaning Speed from Tyre Pressure)Rough speed at which tyres can start to ride up on standing water, from the tyre pressure, with the margin to the speed you drive at.
- AutomotiveQuarter-Mile Horsepower CalculatorEstimated engine power of a car from a quarter-mile run, using both the trap speed and the elapsed time, as drag racers have done for decades.
- AutomotiveRoad Trip Planner Calculator (Days, Breaks and Fuel Stops)How many days a road trip takes, how many breaks and fuel stops it needs, and the total time on the road, from the distance, speed and how long you want to drive each day.
- AutomotiveSuspension Sag Calculator (Mountain Bike and Motorcycle Fork and Shock Setup)How much a fork or shock compresses under your weight, as millimetres and as a share of its travel, compared with the sag you are aiming for.
- AutomotiveTop of Descent Calculator (Where to Start Descending, Rate of Descent)How far from your destination to start descending, and the rate of descent you need, for a given altitude to lose, path angle and ground speed.
- AutomotiveTrue Airspeed Calculator (TAS from Indicated or Calibrated Airspeed)True airspeed from calibrated airspeed, pressure altitude and outside air temperature — how fast the aircraft really moves through the air.
- AutomotiveTurning Radius Calculator (Ackermann Steering)Turning circle of a car, van or trailer from its wheelbase, track width and maximum steering angle, with how tight the inner rear wheel cuts in.
- AutomotiveTyre Tread Life Calculator (How Many Kilometres Until the Legal Limit)Distance and time left before your tyres — or brake pads — reach the legal minimum or the depth where you want to change them, from two measurements.
- AutomotiveTurbo Boost Pressure Ratio CalculatorPressure ratio, absolute pressure and air density gain of a turbocharged or supercharged engine from its boost, the atmospheric pressure and the intake temperature.
- AutomotiveBMEP Calculator (Brake Mean Effective Pressure from Torque and Displacement)The average pressure an engine would need to hold on its pistons throughout the cycle to produce its torque, plus power and output per litre.
- AutomotiveFuel Injector Size CalculatorInjector flow an engine needs for a target power, in cc/min and lb/h, from the number of injectors, the fuel consumption per horsepower and the maximum duty cycle.
- AutomotivePropeller Slip Calculator (Boat Prop Pitch, RPM and Speed)How much a boat propeller slips, from the engine rpm, gear ratio, propeller pitch and the speed through the water, plus the theoretical top speed with no slip.
- AutomotiveRegenerative Braking Energy CalculatorWork out how much energy braking releases and how much of it a car can put back in the battery.
Health & Fitness
Informational body and activity calculators. They never replace a qualified health professional.
- Health & FitnessBMI CalculatorBody mass index, its standard category and the weight range for a BMI of 18.5 to 24.9.
- Health & FitnessBMR and Daily Calorie CalculatorBasal metabolic rate by the Mifflin-St Jeor equation, and daily needs at your activity level.
- Health & FitnessRunning Pace CalculatorPace per kilometre and per mile from a distance and a finishing time, with average speed.
- Health & FitnessWater Intake Reference CalculatorA rough daily water reference from body weight and exercise time.
- Health & FitnessCalories Burned CalculatorEnergy used during an activity from its MET intensity, your weight and the duration.
- Health & FitnessHeart Rate Zones CalculatorEstimated maximum heart rate and the 60, 70, 80 and 90 percent training thresholds.
- Health & FitnessBody Fat Calculator (US Navy Method)Estimated body fat percentage, fat mass and lean mass from neck, waist, hip and height measurements.
- Health & FitnessSleep Cycle CalculatorTime in bed needed for a number of sleep cycles, including the time it takes to fall asleep.
- Health & FitnessCalorie Deficit CalculatorTime to reach a target weight at a chosen daily calorie deficit, and the intake it implies.
- Health & FitnessVDOT Calculator (Jack Daniels' Running Formula)A running-fitness score from any race result, with the oxygen cost of your pace and the share of VO₂max you held, using the published Daniels and Gilbert equations.
- Health & FitnessIdeal Body Weight CalculatorDevine and Robinson ideal weights for both sexes, alongside the healthy BMI weight range.
- Health & FitnessRace Finish Time CalculatorFinish time for any distance from a target pace per kilometre, with the average speed.
- Health & FitnessSteps to Distance CalculatorDistance walked from a step count, with stride length estimated from your height.
- Health & FitnessBlood Alcohol Calculator (Widmark Formula Estimate)A rough estimate of blood alcohol concentration after a number of drinks, from your weight and sex, and how long until it reaches zero.
- Health & FitnessHbA1c to Average Glucose Calculator (eAG, % and mmol/mol)Estimated average blood glucose from an HbA1c result, with the value in both % and mmol/mol and the ADA category.
- Health & FitnessOvulation and Fertile Window Calculator (Cycle-Day Method)The expected day of ovulation and the six-day fertile window from your cycle length, with the days left until each.
- Health & FitnessMacronutrient CalculatorDaily grams of protein, carbohydrate and fat from a calorie target and a percentage split.
- Health & FitnessOne Rep Max CalculatorEstimated maximum single lift from a set, by two published formulas, with common training percentages.
- Health & FitnessGlycemic Load Calculator (Meal GL and Average Glycemic Index)Glycemic load, carbohydrate-weighted glycemic index and total carbohydrate for a meal of up to three foods.
- Health & FitnessLDL Cholesterol Calculator (Friedewald Equation)Estimated LDL cholesterol from total cholesterol, HDL and triglycerides in mg/dL or mmol/L, with non-HDL cholesterol and the NCEP band.
- Health & FitnessMean Arterial Pressure Calculator (MAP and Pulse Pressure)Mean arterial pressure and pulse pressure from a blood pressure reading, with the American blood pressure category.
- Health & FitnessPregnancy Weight Gain Calculator (IOM Recommendations)The recommended weight gain for a single pregnancy from your pre-pregnancy BMI, the range for the week you are at, and where your gain so far falls.
- Health & FitnessBarbell Plate Calculator (Which Plates to Load)How many of each plate to put on each side of a barbell to reach a target weight, for kilogram or pound plates, with what is left over if the target cannot be made.
- Health & FitnessCaffeine Half-Life Calculator (How Much Is Still in Your Body?)How much caffeine is left in your body hours after a coffee, and how long until it falls to a level that will not get in the way of sleep.
- Health & FitnessCycling Speed from Power Calculator (Watts to km/h on Hills and Flat)How fast you will ride on a given gradient for the power you can hold, from your weight, rolling resistance and aerodynamics, and how long a climb will take.
- Health & FitnessGrade Adjusted Pace Calculator (Running Uphill and Downhill)The flat-ground pace that costs the same energy as your pace on a slope, so hill runs can be compared with flat ones, from Minetti's measured cost of running.
- Health & FitnessWaist-to-Height Ratio CalculatorWaist measurement divided by height, with the half-height reference value.
- Health & FitnessWilks and DOTS Score Calculator (Powerlifting Coefficients)Your powerlifting total scaled by bodyweight, as a Wilks score and as a DOTS score, so lifters of different sizes can be compared.
- Health & FitnessMid-Parental Height Calculator (How Tall Will My Child Be?)A prediction of your child's adult height from both parents' heights, using Tanner's mid-parental formula, with a likely range.
- Health & FitnessCycling Power CalculatorThe watts needed to hold a speed, split between air resistance, rolling resistance and the gradient.
- Health & FitnesseGFR Calculator (CKD-EPI 2021 Creatinine Equation)Estimated glomerular filtration rate from serum creatinine, age and sex by the 2021 race-free CKD-EPI equation, with its KDIGO category.
- Health & FitnessHOMA-IR Calculator (Insulin Resistance, HOMA-%B and QUICKI)Insulin resistance by HOMA-IR, beta-cell function by HOMA-%B and the QUICKI sensitivity index from fasting glucose and fasting insulin.
- Health & FitnessSunscreen Amount Calculator (How Much for Your Body?)The amount of sunscreen to cover the skin you leave exposed, using the 2 mg per cm² of the SPF test, plus how many applications a bottle gives.
- Health & FitnessTreadmill Oxygen Cost Calculator (ACSM Walking and Running Equations)Oxygen cost in mL/kg/min, METs and calories for walking or running on a treadmill at a given speed and incline, from the ACSM metabolic equations.
- Health & FitnessKarvonen Target Heart Rate CalculatorTraining heart rate zone from the heart rate reserve method, using your resting pulse.
- Health & FitnessAthlete Carbohydrate Needs Calculator (Grams per Day by Training Load)A daily carbohydrate range in grams from your body weight and how much you train, plus the carbohydrate-loading amount before a long event.
- Health & FitnessCreatinine Clearance Calculator (Cockcroft–Gault)Estimated creatinine clearance in mL/min from age, weight, sex and serum creatinine, the equation behind many drug-dosing tables.
- Health & FitnessCritical Power Calculator (CP and W′ from Two Efforts)Your critical power and W′ from two maximal efforts of different lengths, with the time you can hold a chosen power and predicted 5- and 20-minute powers.
- Health & FitnessFFMI Calculator (Fat-Free Mass Index, Normalised)Fat-free mass index and its height-normalised version from your weight, height and body fat percentage, with lean and fat mass.
- Health & FitnessRace Time Predictor (Riegel Formula)Predicted finish time and pace for a half marathon, marathon or any distance from a recent race result, using Riegel's formula.
- Health & FitnessRucking Calories Calculator (Pandolf Equation)Energy you spend walking with a backpack or weighted vest, from body weight, load, speed, slope and terrain, by the Pandolf equation used by the US Army.
- Health & FitnessSkinfold Body Fat Calculator (Jackson–Pollock 3-Site, Siri Equation)Body fat percentage, body density and fat and lean mass from three skinfold caliper readings, by the Jackson–Pollock 3-site method.
- Health & FitnessSleep Efficiency Calculator (Time Asleep ÷ Time in Bed)Sleep efficiency as a percentage, and total sleep time, from your time in bed, how long you took to fall asleep and how long you were awake.
- Health & FitnessWaist to Hip Ratio CalculatorWaist-to-hip ratio, with the waist measurement that would meet the commonly cited thresholds.
- Health & FitnessAcute:Chronic Workload Ratio Calculator (ACWR for Training Load)Your acute:chronic workload ratio from four weeks of training load, with its zone, the largest sensible load for next week and the week-on-week change.
- Health & FitnessAerobic Decoupling Calculator (Pa:Hr Cardiac Drift)How much your pace-to-heart-rate efficiency fell from the first half of a steady run or ride to the second, from the average speed or power and heart rate of each half.
- Health & FitnessSWOLF and Stroke Index Calculator (Swimming Efficiency)SWOLF, distance per stroke, stroke rate and Costill's stroke index from your time and stroke count for one pool length.
- Health & FitnessVO2max Calculator from Heart Rate (Uth Method)Estimated maximal oxygen uptake from the ratio between your maximum and resting heart rate, with no running or cycling test.
- Health & FitnessABSI and Body Roundness Index Calculator (Waist-Based Risk Indices)A Body Shape Index and Body Roundness Index from waist, height and weight, two measures that use the waist to say more than BMI does.
- Health & FitnessBody Surface Area CalculatorBody surface area by the Mosteller, Du Bois and Haycock formulas, with the BMI alongside.
- Health & FitnessRelative Fat Mass (RFM) CalculatorEstimated body fat percentage from height and waist circumference, by the RFM equation, with the fat and fat-free mass for your weight.
- Health & FitnessSwimming Pace CalculatorPace per 100 metres, speed, number of lengths and the average time per length.
- Health & FitnessCooper Test VO₂ Max CalculatorEstimated VO₂ max from the distance covered in a 12-minute run, with the MET equivalent.
- Health & FitnessLean Body Mass Calculator (Boer Formula)Lean mass, fat mass and implied body fat percentage from height, weight and sex.
- Health & FitnessHiking Time Calculator (Naismith's Rule)How long a hill walk will take from its distance and total climb, using Naismith's rule, with your own pace if you know it.
- Health & FitnessWBGT Calculator (Wet-Bulb Globe Temperature)Heat stress index from the natural wet-bulb, black globe and air temperatures, outdoors or indoors, with the US Army heat category flag.
- Health & FitnessBody Adiposity Index (BAI) CalculatorEstimated body fat percentage from hip circumference and height alone, and the fat and fat-free mass it implies for your weight.
- Health & FitnessTotal Body Water Calculator (Watson Formula)Litres of water in your body from sex, age, height and weight, by the Watson equations, and the fat-free and fat mass that implies.
- Health & FitnessTRIMP Calculator (Banister Training Impulse)A single number for how hard a session was, from its length and your average heart rate, using the Banister exponential weighting of the heart rate reserve.
- Health & FitnessTSS Calculator (Training Stress Score for Cycling)Training Stress Score and intensity factor of a ride from its duration, normalized power and your FTP, with the equivalent minutes at threshold.
- Health & FitnessCritical Swim Speed (CSS) CalculatorYour critical swim speed and the matching pace per 100 m from just a 400 m and a 200 m time trial, plus the anaerobic distance capacity.
- Health & FitnessFTP and Cycling Power Zones CalculatorFunctional threshold power from a 20-minute test, watts per kilogram, and the training zones built on it.
- Health & FitnessRowing Pace and Watts Calculator (Concept2 Ergometer)Convert a rowing split per 500 m into watts, speed and a 2000 m time, or turn a power in watts back into the split it corresponds to.
- Health & FitnessStride Length Calculator (Running Step Length from Speed and Cadence)Step length, stride length and steps per kilometre or mile from your running or walking speed and your cadence.
- Health & FitnessSweat Rate CalculatorHow much fluid you lose per hour of exercise, from your weight before and after, what you drank and the duration.
- Health & FitnessVAM Calculator (Climbing Speed and Estimated W/kg)Average climbing speed in vertical metres per hour, the gradient, and a rough estimate of the watts per kilogram that it takes.
- Health & FitnessRockport Walk Test Calculator (VO₂max)Estimated aerobic fitness (VO₂max) from the Rockport one-mile walk test: walk 1609 m as fast as you can and note the time and your heart rate at the finish.