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Mach Number Calculator

Find an object's Mach number — its speed as a multiple of the local speed of sound — from its velocity and the air temperature, with the standard subsonic/transonic/supersonic/hypersonic classification.

Mach number
0.882
Flight regime
Transonic
Speed of sound at this temperature
340.3 m/s

Where this falls

0.9 falls in the "Transonic" range.

How it works

Mach number is just velocity divided by the local speed of sound: M = v / a. It's a ratio, not a speed — Mach 1 means 'exactly as fast as sound travels right now,' whatever that speed happens to be at the current air temperature.

The speed of sound in air depends on temperature through a = 331.3 × √(1 + T/273.15) m/s, where T is the air temperature in Celsius and 331.3 m/s is the speed of sound at 0°C — colder air is denser and transmits sound slightly slower, warmer air slightly faster. This calculator converts any entered velocity to meters per second, computes the speed of sound at the entered temperature, and divides.

The resulting Mach number is classified using the standard aerodynamic convention: below Mach 0.8 is subsonic, 0.8–1.2 is transonic (airflow over parts of a vehicle first reaches the speed of sound even though the vehicle itself hasn't), 1.2–5.0 is supersonic, and above Mach 5 is hypersonic.

FAQ

Why does the same speed give a different Mach number on a hot day versus a cold day?

Because Mach number is relative to the speed of sound, which itself depends on temperature. The same 300 m/s is a lower Mach number on a hot day (sound travels faster through warmer air) than on a cold day — this is why aircraft performance data is usually quoted in Mach number rather than raw airspeed, and why a jet's Mach limit corresponds to different ground speeds at different altitudes and temperatures.

Why isn't the temperature field affected by the metric/imperial toggle?

Because it's an absolute reading, not a difference — converting it correctly needs an offset (°F = °C × 1.8 + 32), and this site's unit toggle only supports a straight multiplicative scale factor. Velocity is a pure ratio between units, so it toggles normally; temperature stays in Celsius either way.

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