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Air Pressure Altitude Calculator

Calculate air pressure, density and boiling point at a given altitude.

About Air Pressure Altitude Calculator

Pressure falls roughly exponentially with altitude, reaching about three quarters of sea level at 2,500 metres. Water boils lower as a direct consequence, which is why cooking times lengthen in the mountains. Oxygen remains 21 per cent of the air at any altitude; it is the falling pressure rather than the composition that causes altitude sickness.

Formula

Air Pressure Altitude

Pressure = sea level pressure × (1 − 2.25577×10⁻⁵ × altitude)^5.25588

barometric formula
The standard atmosphere pressure model
boiling point
Falls about one degree per 285 metres of altitude

Worked example

With the default values below, Air Pressure Altitude Calculator returns Air Pressure of 746.825. Change any input above and every figure here is recalculated in your browser.

Inputs used

Altitudeaccepts -500–11,000 m
2,500 m
Sea level pressureaccepts 800–1,100 hPa
1,013.25 hPa
Air temperatureaccepts -60–50 C
8 C

Results

Air Pressure
746.825 hPa
Pressure as a Share of Sea Level
73.706%
Air Density
0.92539 kg/m3
Water Boiling Point
91.23 C
Oxygen Partial Pressure
156.460 hPa

Step by step

  1. 1Values used
  2. 2Air Pressure Altitude
  3. 3Air Pressure= 746.825 hPa
  4. 4Pressure as a Share of Sea Level= 73.706
  5. 5Air Density= 0.92539 kg/m3
  6. 6Water Boiling Point= 91.23 C
  7. 7Oxygen Partial Pressure= 156.460 hPa

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Air Pressure Altitude calculated?

Pressure = sea level pressure × (1 − 2.25577×10⁻⁵ × altitude)^5.25588 Pressure falls roughly exponentially with altitude, reaching about three quarters of sea level at 2,500 metres. Water boils lower as a direct consequence, which is why cooking times lengthen in the mountains.

Why does Air Pressure Altitude matter?

Oxygen remains 21 per cent of the air at any altitude; it is the falling pressure rather than the composition that causes altitude sickness.

What values do I need to enter?

This calculator takes 3 inputs: Altitude, Sea level pressure, Air temperature. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.

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