Air pressure falls with height because there is less air above you. At 5,500 m – roughly Everest base camp – it is half the sea-level value; at airliner cruise height about a quarter.
How to use the Air Pressure at Altitude Calculator
- Altitude h
- Sea-level pressure p₀
- Sea-level temperature T₀
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter the altitude, the sea-level pressure and the sea-level temperature (valid in the troposphere, up to 11 km).
Inputs explained
| Field | What to enter |
|---|---|
| Altitude h | Units: m, ft, km |
| Sea-level pressure p₀ | Units: hPa, kPa, inHg, mmHg, psi, atm |
| Sea-level temperature T₀ | Units: °C, °F, K |
What each result means
- Air pressure at altitude = [Sea-level pressure p₀]×(1 – 0.0065×[Altitude h]÷([Sea-level temperature T₀] + 273.15))^5.25588
- Fraction of sea-level pressure = [Air pressure at altitude]÷[Sea-level pressure p₀]×100
- Standard temperature at altitude = [Sea-level temperature T₀] – 0.0065×[Altitude h]
Example values
How the main result changes when Altitude h changes and everything else stays at the example values above:
| Altitude h (m) | Air pressure at altitude (hPa) |
|---|---|
| 750 | 926.3361 |
| 1,125 | 885.2022 |
| 1,500 | 845.5599 |
| 1,875 | 807.3677 |
| 2,250 | 770.5844 |
| 3,000 | 701.0853 |
Formula
p = p₀·(1 − L·h/T₀)^{g·M/(R·L)}, L = 0.0065 K/m, exponent ≈ 5.2559
Worked example
Inputs — Altitude h: 1,500 m; Sea-level pressure p₀: 1,013.25 hPa; Sea-level temperature T₀: 15 °C.
Results — Air pressure at altitude = 845.55994 hPa; Fraction of sea-level pressure = 83.4503 %; Standard temperature at altitude = 5.25 °C.
Key terms
- Barometric formula
- Pressure as a function of height in the atmosphere.
Frequently asked questions
At what altitude is pressure half of sea level?
About 5,500 m.
Why does water boil at a lower temperature on mountains?
Lower pressure lowers the boiling point.
Is the formula valid above 11 km?
No – the stratosphere has a different temperature profile.
What is the cabin pressure of an airliner?
Equivalent to about 1,800–2,400 m.