Mach Number Converter

Convert a speed into a Mach number, or the other way round. Mach is a ratio to the local speed of sound, not a fixed speed, so this asks for the air temperature: Mach 1 is about 340 m/s at 15 °C and about 295 m/s at -50 °C.

Convert speed and Mach number

Enter the details
°C

Related Calculators

Speed Unit Converter KPH to MPH Converter Knots Converter Metres per Second to Feet per Second Converter

Frequently Asked Questions

The ratio of a speed to the speed of sound in the air around it. Mach 2 means twice the local speed of sound.

Because the speed of sound depends on it, and on nothing else that matters here. It is about 340 m/s at 15 °C and about 295 m/s at -50 °C, which is roughly the temperature at cruising altitude. The same aircraft at the same ground speed has a higher Mach number up there.

Not directly. For an ideal gas the speed of sound depends on temperature alone. Altitude matters because it is colder up there, not because the air is thinner.

a = √(γRT), with γ = 1.4 for air, R = 287.05 J/(kg·K) and T in kelvin. At 15 °C that gives 340.3 m/s, the standard sea-level figure.