Temperature at Altitude Calculator

In the troposphere (0–11 km), temperature decreases with altitude at roughly 6.5°C per 1,000 meters. Above that, in the stratosphere, temperature actually increases with altitude due to ozone absorbing solar radiation. The relationship becomes complex in higher layers, making the ISA model a useful standard approximation.

Yes. In the troposphere the standard formula is T = T₀ + L × h, where T₀ is sea-level temperature, L is the lapse rate (−6.5 °C/km), and h is altitude in km. Different atmospheric layers have different lapse rates — some positive, some zero (isothermal), some negative — which the ISA model defines precisely.

The Earth's surface absorbs solar radiation and warms the air nearest to it. As you rise, you move farther from this heat source, and the air pressure drops, causing air to expand and cool adiabatically. This results in the standard lapse rate of about 6.5°C per 1,000 meters.

The stratosphere (11–47 km) contains the ozone layer, which absorbs ultraviolet radiation from the sun. This absorption generates heat, causing temperatures to rise with altitude rather than fall. At the stratopause (~47 km), temperatures can reach around 0°C despite the extreme height.

The ISA is a standardized model adopted by aviation and meteorology that defines how temperature, pressure, and density vary with altitude under idealized conditions. It divides the atmosphere into layers, each with a specific lapse rate, providing a consistent reference for aircraft performance calculations and weather analysis.

At 35,000 feet (~10,668 m), which is in the upper troposphere near the tropopause, the standard ISA temperature is approximately −56.5°C (−69.7°F). This is why aircraft cabins are pressurized and insulated — the outside air is extremely cold and thin.

In the mesosphere (51–86 km), temperature decreases again with altitude, reaching the coldest temperatures in Earth's atmosphere — around −90°C at the mesopause (~86 km). This is the highest point modeled in the standard ISA tables.

Geopotential altitude accounts for the slight decrease in gravitational acceleration as you move away from Earth's surface. At low to moderate altitudes, the difference is negligible, but for precision calculations above ~20 km, geopotential altitude gives a more physically accurate representation for pressure and temperature modeling.