How thin is the air up there? The International Standard Atmosphere is the reference every altimeter, airspeed indicator, and engine is calibrated against.
Standard Atmosphere (ISA)Live
temperature, pressure, density
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The International Standard Atmosphere is the reference model all aircraft and instruments are calibrated against. Temperature falls steadily through the troposphere at 6.5 °C/km, then holds constant in the stratosphere above the tropopause. Pressure and density decay roughly exponentially — at airliner altitude the air is only a quarter as dense as at sea level.
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How it works
The ISA models temperature falling at 6.5 °C/km through the troposphere, then holding constant in the stratosphere above the 11 km tropopause. Pressure and density decay nearly exponentially — at airliner cruise the air is only a quarter as dense as at sea level, which sets true airspeed, lift, and engine performance.
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The math, the assumptions, real-world uses, or a code translation — explained for this exact simulation.
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Yes. Standard Atmosphere (ISA) runs entirely in your browser using your device's own compute, so local use is free forever. You only pay Compute Tokens if you scale a job to the cloud.
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The solver uses established numerical methods, but results are for research and educational purposes and should be validated against experiment or professional review before you rely on them.