Mach Speed Calculator

About this calculator

The Mach number expresses speed as a ratio to the local speed of sound: M = v ÷ a, where a is roughly 343 m/s (1,235 km/h) at sea level and 15°C, but decreases with altitude as air temperature drops. Flight regimes are classified by Mach number: subsonic (below ~0.8), transonic (0.8–1.2, where shock waves start forming), supersonic (1.2–5), and hypersonic (above 5).

Aerospace engineers use Mach number because aerodynamic behavior — drag, shock wave formation, control surface response — changes fundamentally near and above the speed of sound, unlike behavior at fixed absolute speeds. Pilots, aviation enthusiasts, and engineering students use this calculator to convert a speed (in km/h, mph, or m/s) into its Mach number and see which flight regime it falls into. Enter the speed and altitude/temperature to get the result.