Climb a mountain and it gets colder – on average 6.5 °C for every kilometre. Above about 11 km, in the stratosphere, temperature stops falling. That is why airliners cruise in air around −55 °C.
How to use the Temperature at Altitude Calculator
- Temperature at the ground
- Ground elevation
- Target altitude
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter the ground temperature, the ground elevation and the target altitude.
Inputs explained
| Field | What to enter |
|---|---|
| Temperature at the ground | Units: °C, °F, K |
| Ground elevation | Units: m, ft |
| Target altitude | Units: m, ft, km |
What each result means
- Temperature at altitude = [Temperature at the ground] – 0.0065×(min([Target altitude], 11000) – [Ground elevation])
- Temperature change = -0.0065×(min([Target altitude], 11000) – [Ground elevation])
Example values
How the main result changes when Temperature at the ground changes and everything else stays at the example values above:
| Temperature at the ground (°C) | Temperature at altitude (°C) |
|---|---|
| 10 | -9.5 |
| 15 | -4.5 |
| 20 | 0.5 |
| 25 | 5.5 |
| 30 | 10.5 |
| 40 | 20.5 |
Formula
T(h) = T₀ − 6.5 °C/km × (h − h₀) (up to 11 km), then constant at T₀ − 71.5 °C
Worked example
Inputs — Temperature at the ground: 20 °C; Ground elevation: 0 m; Target altitude: 3,000 m.
Results — Temperature at altitude = 0.5 °C; Temperature change = -19.5 K.
Key terms
- Lapse rate
- Rate of temperature decrease with height.
Frequently asked questions
Why does air cool with height?
Rising air expands at lower pressure and cools.
Is the lapse rate always 6.5 °C/km?
No – it varies; temperature inversions can even reverse it.
How cold is it at 10 km?
About −50 °C in the standard atmosphere.
What is the tropopause?
The boundary at ~11 km where temperature stops falling.