Calculates how many times the local speed of sound an object is traveling.
How it works
The object’s velocity is divided by the local speed of sound to give the Mach number.
What this does not include
This does not include computing the speed of sound itself from temperature — for that, use this site’s speed of sound calculator first, then enter the result here.
How to use this calculator
- Enter the object’s velocity and the local speed of sound.
A worked example
An object traveling 686 m/s where the speed of sound is 343 m/s → 686 ÷ 343 = Mach 2 — twice the speed of sound.
1,000 m/s against a speed of sound of 340 m/s → Mach 2.9412.
What the variables mean
| Variable | Meaning |
|---|---|
| Velocity | The object’s actual speed |
| Speed of sound | The local speed of sound, which varies with air temperature and altitude |
Edge cases worth knowing
The speed of sound isn’t a fixed constant — it changes with temperature and altitude, which is why this calculator takes it as an input rather than assuming a single sea-level value.
Mach 1 is the speed of sound itself, not a fixed velocity. The same aircraft speed can be a different Mach number at different altitudes, since the speed of sound itself changes.
Frequently asked questions
What does “Mach 1” mean?
Traveling at exactly the local speed of sound — Mach 2 means twice the speed of sound, and so on.
Why does “the” speed of sound vary?
The speed of sound depends on air temperature (and to a lesser extent, humidity and altitude), so the same aircraft speed corresponds to a different Mach number depending on conditions.
What’s the difference between subsonic and supersonic?
Subsonic means traveling slower than the speed of sound (Mach number under 1); supersonic means faster (Mach number over 1).
