Temperature at Altitude Calculator

How Does Temperature Change with Altitude?

In the lower atmosphere (troposphere), temperature generally falls with height. The International Standard Atmosphere (ISA) uses a constant lapse rate of 6.5 °C per kilometer below 11 km.

Altitude Temperature Formula

$$T = T_0 - L \cdot h$$

where $T_0 = 15$ °C is ISA sea-level temperature, $L = 6.5$ °C/km is the lapse rate, and $h$ is altitude in kilometers. At 3000 m (3 km), temperature drops by 19.5 °C to about −4.5 °C.

Pilots and engineers use ISA as a reference atmosphere. Real weather deviates, but the lapse rate gives a useful baseline for performance calculations.

Frequently Asked Questions

What is the ISA lapse rate?

6.5 °C per kilometer (3.57 °F per 1000 ft) in the troposphere. It means air cools as it rises and expands adiabatically in the standard model.

Does temperature always drop with altitude?

In the troposphere, generally yes. Above ~11 km (stratosphere), temperature can rise due to ozone absorption of UV radiation.

Can I change sea-level temperature?

Yes. ISA uses 15 °C, but enter your local surface temperature to estimate temperature at altitude relative to current conditions.

Why is this important for aviation?

Aircraft performance, icing risk, and engine power depend on air temperature. ISA deviations (ISA+10, ISA−10) are standard in flight planning.

How cold is it at cruising altitude?

At 10 km (~33,000 ft), ISA temperature is about −50 °C. Commercial jets cruise near the tropopause where temperatures are coldest.

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Altitude Temperature Calculator

How Does Temperature Change with Altitude?

Altitude Temperature Formula

Frequently Asked Questions

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