Case 1
- Object speed
- 343m/s
- Local speed of sound
- 343m/s
1.000
Open with these valuesMach Number Calculator
1.000
Result: 1.000The Mach number is one speed divided by another, so it has no units: Mach 2 is twice the local speed of sound in any unit system. What counts as Mach 1 changes with the medium and its temperature — 343 m/s in air at 20 °C, about 295 m/s at cruising altitude.
Worked examples
Case 2
- Object speed
- 250m/s
- Local speed of sound
- 295m/s
0.847
Open with these valuesCase 3
- Object speed
- 1715m/s
- Local speed of sound
- 343m/s
5.000
Open with these valuesHow it's calculated
M = u ÷ c
- StepEnter the object's speed.
- StepEnter the speed of sound where the object actually is, in the same unit.
- ResultRead the Mach number: below 1 subsonic, above 1 supersonic, above 5 hypersonic.
Reference table
| Speed, speed of sound | Regime | Mach |
|---|---|---|
| 171.5, 343 | Subsonic | 0.500 |
| 250, 295 | Airliner at cruising altitude | 0.847 |
| 343, 343 | Sonic — the sound barrier | 1.000 |
| 686, 343 | Supersonic | 2.000 |
| 600, 295 | Concorde at altitude | 2.034 |
| 1715, 343 | Hypersonic | 5.000 |
Questions
How do I calculate the Mach number?
Divide the object's speed by the local speed of sound: M = u ÷ c. Use the same units for both speeds so they cancel and the Mach number is dimensionless. For example, an object at 686 m/s where sound travels 343 m/s has 686 ÷ 343 = Mach 2.
What is the Mach number?
The Mach number is the ratio of an object's speed to the speed of sound in the medium around it, named after the physicist Ernst Mach. A Mach number of 1 means the object is moving at exactly the speed of sound. It is dimensionless, so it has no units.
What do subsonic, supersonic and hypersonic mean?
They are flight regimes set by the Mach number: subsonic is below Mach 1, sonic is exactly Mach 1, supersonic is above Mach 1 and hypersonic is above Mach 5. Each regime brings very different aerodynamic behaviour.
What value should I use for the speed of sound?
It depends on the medium and its temperature. In dry air at 20 °C the speed of sound is about 343 m/s, but it falls to roughly 295 m/s in the cold thin air at cruising altitude and to 331 m/s at 0 °C. Use the value that matches your actual conditions, or the Mach number will be wrong even though the division is right.
Does the Mach number have units?
No. Because the Mach number divides one speed by another, the units cancel and the result is dimensionless — Mach 2 means twice the speed of sound in any unit system. Just make sure you enter both speeds in the same unit.
Sources and last check
Information, not professional advice.