MAXScanner physics & engineering calculator
Mach Number Calculator — Speed, Temperature & Speed of Sound
Calculate Mach number from object speed and air temperature, or convert a target Mach number back to speed using the ideal-gas speed of sound.
Last updated: September 17, 2026
Results
Enter non-negative speed and temperature above absolute zero
Formula, example and assumptions
a=√(γRT); M=v/a, using γ=1.4 and R=287.05 J/(kg·K) for dry air.
At 15°C, the ideal dry-air speed of sound is about 340 m/s, so 170 m/s is roughly Mach 0.5.
- The dry-air ideal-gas approximation ignores humidity and detailed atmospheric composition.
- Local speed of sound depends mainly on absolute temperature; altitude matters indirectly through atmospheric temperature.
Frequently asked questions
Is Mach 1 always the same speed?
No. Mach 1 equals the local speed of sound, which changes with temperature and gas composition.
Does pressure appear in this formula?
For an ideal gas the common speed-of-sound expression can be written using temperature, γ and the specific gas constant without an explicit pressure term.