About the Altitude and Air Pressure Calculator
Air gets thinner as you climb, so the pressure falls. This calculator uses the international standard atmosphere to give the air pressure at a height above sea level, the standard temperature and the temperature at which water boils. In reverse, it finds the height for a given pressure, as a barometric altimeter does. Type a height above sea level, or an air pressure and the air pressure at altitude appears at once, with a few related figures underneath, and you can copy the result with one tap. The sums run in your browser, so nothing you enter is uploaded.
Updated October 2026
How to use the Altitude and Air Pressure Calculator
- 1Enter a height above sea level, or an air pressure.
- 2Pick the units or options from the menus if the air pressure at altitude tool offers them.
- 3Read the air pressure at altitude in the large result box.
- 4Look at the extra rows for related figures.
- 5Press Copy result to keep the answer.
When you need the air pressure at altitude
Hikers, pilots, cooks at altitude and weather enthusiasts use it. Cooks learn why boiling takes longer in the mountains.
The model is valid up to about 11,000 m, the end of the lowest layer. Real pressure at a given height changes with the weather by up to about 30 hPa.
How the air pressure at altitude is worked out
p = 101,325 Pa × (1 − 2.25577 × 10⁻⁵ × h)^5.25588, with h in metres. The standard temperature falls 6.5 °C per kilometre from 15 °C. At 3,000 m the pressure is about 701 hPa, the standard temperature is −4.5 °C and water boils at roughly 90 °C. A pressure of 700 hPa corresponds to about 3,010 m.
Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.
- Two directions
- Boiling point at altitude
- Standard temperature
Mistakes to avoid with air pressure at altitude
Do not confuse pressure at your height with sea-level pressure, which weather reports use. A weather report's pressure has already been adjusted to sea level.
On phone and computer
On a phone, type into the boxes one after another and read the air pressure at altitude underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the air pressure at altitude move. The altitude and air pressure calculator works the same on both.
Checking your air pressure at altitude by hand
A good habit is to test the altitude and air pressure calculator with a case you already know. At 3,000 m the pressure is about 701 hPa, the standard temperature is −4.5 °C and water boils at roughly 90 °C. A pressure of 700 hPa corresponds to about 3,010 m.
If your own figures give a surprising answer, repeat the working yourself: p = 101,325 Pa × (1 − 2.25577 × 10⁻⁵ × h)^5.25588, with h in metres. The standard temperature falls 6.5 °C per kilometre from 15 °C. Small differences usually come from rounding, from mixing units, or from a typing slip in one of the inputs. Pressure is only one half of a weather or hiking plan. Switch units afterwards with the Pressure Converter, and use the Temperature Converter when a source quotes degrees in a different scale. If you work with gases, the Ideal Gas Law Calculator shows how pressure, volume and temperature relate.
Features
- Valid to 11,000 m
- Weather shifts real pressure
- Sea level vs station pressure
- Clear messages when the air pressure at altitude inputs make no sense
- Copy the result with one tap
- Private: nothing is uploaded
Frequently asked questions
How do I calculate air pressure at altitude?
p = 101,325 Pa × (1 − 2.25577 × 10⁻⁵ × h)^5.25588, with h in metres. The standard temperature falls 6.5 °C per kilometre from 15 °C. At 3,000 m the pressure is about 701 hPa, the standard temperature is −4.5 °C and water boils at roughly 90 °C. A pressure of 700 hPa corresponds to about 3,010 m.
What is the formula for air pressure at altitude?
p = 101,325 Pa × (1 − 2.25577 × 10⁻⁵ × h)^5.25588, with h in metres. The standard temperature falls 6.5 °C per kilometre from 15 °C. The altitude and air pressure calculator applies it exactly and rounds only the displayed answer to six significant figures.
Why does water boil at a lower temperature at altitude?
The air pressure is lower, so less heat is needed to form vapour.
How fast does pressure fall?
About 12 hPa per 100 m near sea level.
Is this exact?
It is the standard atmosphere, so real weather causes small differences.
Is this altitude and air pressure calculator free and private?
Yes. It is free, needs no account and runs in your browser, so the numbers you type are not uploaded or stored.