88 tools
Science
Astronomy, earth science, biology and the environment: distances between stars, earthquake energy, population growth and air quality.
Tools in this category
- 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.