How do you convert Mach to MPH?

To convert Mach to miles per hour, multiply the Mach number by the local speed of sound in mph. For example, at sea level Mach 1 ≈ 761.2 mph, so Mach 2 ≈ 1522.4 mph.

Why does the result depend on altitude?

Mach is a ratio to the speed of sound, and the speed of sound changes with temperature. At higher altitudes the air is colder, the speed of sound is lower, so the same Mach corresponds to a lower mph value.

Can I use a custom speed of sound?

Yes. If you know the speed of sound for your conditions (mph), you can enter it and the tool will do Mach × speed_of_sound.

Mach to MPH Converter

Convert a Mach number (ratio to speed of sound) into miles per hour. Choose altitude/atmosphere or specify a custom speed of sound for more accurate aerospace calculations.

Convert speed

Mach number unitless

Atmosphere / condition

Result

Speed: –

Speed of sound used: –

This assumes dry air and ISA temperature profile. Real aircraft performance may differ.

Need the opposite? Try MPH to Mach.

Formula used

Mach is a ratio, so to go from Mach to a real-world speed you multiply:

speed (mph) = Mach × speed_of_sound (mph)

The only thing to decide is what speed of sound to use. That depends on temperature, which depends on altitude.

Typical speed of sound values (mph)

Sea level: ~761.2 mph
10,000 ft: ~734 mph
20,000 ft: ~707 mph
30,000 ft: ~679 mph
36,000 ft: ~661 mph

So, for example, Mach 2 at sea level ≈ 2 × 761.2 = 1522.4 mph.

FAQ

Is Mach 1 always 761 mph?

No. 761 mph is a good sea-level ISA reference. At altitude the speed of sound is lower, so Mach 1 is lower in mph.

Can I use km/h instead?

Yes, but then you must use speed of sound in km/h. In this tool we stay in mph for consistency with your input.

Why does aviation care about Mach?

Because aerodynamic effects (compressibility, shock waves) depend on speed relative to the speed of sound, not just absolute mph or knots.