When is it useful?
Mach number compares speed with the speed of sound in the surrounding medium. It is useful in aircraft, nozzles, and other high-speed gas flows when judging whether compressibility matters.
Formula and inputs
Enter relative object or flow speed v and local sound speed c, both in m/s. The sound speed depends on the gas and its temperature, so 340 m/s is not a universal constant.
Open this calculatorWorked example
If v = 170 m/s and c = 340 m/s under the stated conditions, Ma = 170 ÷ 340 = 0.5. This means the speed is half the local sound speed; it is not a fixed absolute speed for all conditions.
Interpreting the result
Ma below 1 is broadly subsonic; near 1, transonic effects may need attention. The calculator gives convenient regime labels, while local flow around an object may differ from the free-stream Mach number.
Limits and cautions
A change in altitude, temperature, or medium may change c even if v remains the same. This ratio alone cannot predict shock position, pressure, drag, or safety.
Formula and concept reference: NASA Glenn — Role of the Mach Number. We created the sample inputs and calculations for this guide.