Enter a value in any box. This calculator uses 340.29 m/s (1,225.044 km/h) for Mach 1, corresponding to standard sea-level conditions at 15°C.
Mach 1 = 340.29 m/s = 1,225.044 km/h = 761.207 mph = 661.459 knots
Standard Sea-Level Examples
These examples use the same 15°C standard sea-level reference as the calculator. They are quick conversions, not flight-envelope limits: Mach 0.8 is about 980 km/h, Mach 2 is about 2,450 km/h, Mach 3 is about 3,675 km/h, and Mach 5 is about 6,125 km/h. At typical high-altitude temperatures, the corresponding true airspeeds are lower because the local speed of sound is lower.
Why Mach changes with altitude
The Mach number compares true airspeed with the local speed of sound. That speed is governed primarily by air temperature. In colder upper-air conditions, Mach 1 corresponds to fewer km/h than it does at warm sea level. For flight planning or engineering, use atmospheric temperature at the actual altitude rather than a single shortcut conversion.
After converting a speed, explore the complete aircraft speed comparison or use the aircraft comparison tool.