Altitude Temperature Calculator
The International Standard Atmosphere cools by about 6.5 °C per 1,000 m of climb. Enter a known temperature and altitude, then a target altitude.
Result
- Temperature change
- 8.1 °F
How the calculation works
One line of atmospheric physics, applied to your two altitudes:
The 6.5 °C/km figure is the International Standard Atmosphere's environmental lapse rate, an average over the lower troposphere. The calculator works in both directions - climbing cools, descending warms - and in °C or °F.
Where the number fits into trip planning: pair the estimated camp temperature with the warmth calculator to check your sleep system, and with the wind chill calculator for exposed travel. The altitude cooking guide covers what the same altitude does to your stove and your pasta.
Planning estimate only - not safety advice.
Frequently asked questions
Why does temperature fall with altitude?
Rising air expands and cools - roughly 6.5 °C per 1,000 m on average in the troposphere (the environmental lapse rate the International Standard Atmosphere uses). The air is not "closer to space" in any meaningful way at hiking altitudes; it is mostly an expansion effect.
How reliable is the 6.5 °C per 1,000 m number?
As an average, very; as a forecast, sometimes not. Inversions make valleys colder than ridges, especially on clear calm nights - the opposite sign of the model. Frontal weather and foehn winds break it too. Use the estimate for trip planning, not for a specific hour.
Can I use it to convert a summit forecast?
Yes - that is the classic use. If the valley forecast says 18 °C at 500 m and your camp is at 2,500 m, expect roughly 18 − 6.5 × 2 = 5 °C. Combine with the <a href="/wind-chill-calculator/">wind chill calculator</a> for what it will feel like above treeline.
Does the lapse rate change at night?
The surface layer does: clear nights cool the ground fast, and the coldest air drains downhill. That is why valley bottoms frost first. The standard rate describes the free atmosphere better than the last few hundred meters above the ground.