Sea-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.
Results
The dashed line marks the value you entered.
What this tool does
A barometer at 500 m reads about 58 hPa less than one at the coast in the same weather, since you are under less air, so station pressure cannot be compared directly with a forecast. Meteorologists reduce it to what the pressure would be at sea level, using the elevation and temperature — about 12 hPa per 100 m near the ground. Many home weather stations ask for the altitude for exactly this reason, and a reading that looks low on a hill is usually just uncorrected.
Formula
P₀ = P × [1 − 0.0065 h ÷ (T + 0.0065 h + 273.15)]^−5.257 (h in m, T in °C)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
pr | Pressure read at your station | hPa |
he | Elevation of the place | m |
te | Air temperature | °C |
P0 | Pressure reduced to sea level | hPa |
DP | Correction added to your reading | hPa |
IH | Sea-level pressure in inches of mercury | inHg |
MM | Sea-level pressure in mmHg | mmHg |
Worked example
- Pressure read at your station950 hPa
- Elevation of the place500 m
- Air temperature15 °C
- Pressure reduced to sea level1007.7 hPa
- Correction added to your reading57.7 hPa
- Sea-level pressure in inches of mercury29.76 inHg
- Sea-level pressure in mmHg755.8 mmHg
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- Mixing units is the most common source of error. Convert every input to the units shown next to each field before calculating.