# Air Pressure at Altitude Calculator

URL: https://speedycalculator.com/calculators/physics/air-pressure-at-altitude/
Last updated: 2026-10-30

> The air pressure at altitude calculator finds atmospheric pressure at a given height using the barometric formula of the standard atmosphere, from the sea-level pressure and temperature.

## Inputs

- Altitude h (m, ft, km)
- Sea-level pressure p₀ (hPa, kPa, inHg, mmHg, psi, atm)
- Sea-level temperature T₀ (°C, °F, K)

## Results

- Air pressure at altitude
- Fraction of sea-level pressure
- Standard temperature at altitude

## Formula

```
p = p₀·(1 − L·h/T₀)^{g·M/(R·L)},  L = 0.0065 K/m,  exponent ≈ 5.2559
```

## Explanation

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

FieldWhat to enterAltitude hUnits: m, ft, kmSea-level pressure p₀Units: hPa, kPa, inHg, mmHg, psi, atmSea-level temperature T₀Units: °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)750926.33611,125885.20221,500845.55991,875807.36772,250770.58443,000701.0853

## 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.

## FAQ

**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.


## Sources

- [U.S. Standard Atmosphere 1976 (NOAA/NASA/USAF)](https://ntrs.nasa.gov/citations/19770009539)
- [NOAA / National Weather Service – Weather calculators](https://www.weather.gov/epz/wxcalc)