km/h to Mach Converter
Convert kilometres per hour to Mach number, at the sea-level speed of sound. Results update as you type; exact factors shown.
One kilometre per hour is 0.0008 Mach (sea level, 15 °C) — see the exact factor, not a rounded rule of thumb.
How the km/h to mach converter works
Speeds convert through metres per second. 1 km/h is 1000/3600 m/s; 1 mph is 1609.344/3600 m/s; a knot is one nautical mile (1,852 m) per hour. Mach is shown against the standard sea-level speed of sound of 340.29 m/s and varies with altitude and temperature.
The UK is metric for most trade and science but keeps miles, pints, stone and mpg (with the imperial gallon) in daily life.
Common speed conversions
| From | To | Units |
|---|---|---|
| 100 km/h | 0.0816 Ma | kilometres per hour to Mach (sea level, 15 °C) |
| 300 km/h | 0.2449 Ma | kilometres per hour to Mach (sea level, 15 °C) |
| 500 km/h | 0.4081 Ma | kilometres per hour to Mach (sea level, 15 °C) |
| 800 km/h | 0.653 Ma | kilometres per hour to Mach (sea level, 15 °C) |
| 900 km/h | 0.7347 Ma | kilometres per hour to Mach (sea level, 15 °C) |
| 1,000 km/h | 0.8163 Ma | kilometres per hour to Mach (sea level, 15 °C) |
| 1,225 km/h | 1 Ma | kilometres per hour to Mach (sea level, 15 °C) |
| 1,500 km/h | 1.2244 Ma | kilometres per hour to Mach (sea level, 15 °C) |
| 2,000 km/h | 1.6326 Ma | kilometres per hour to Mach (sea level, 15 °C) |
| 2,500 km/h | 2.0407 Ma | kilometres per hour to Mach (sea level, 15 °C) |
| 3,000 km/h | 2.4489 Ma | kilometres per hour to Mach (sea level, 15 °C) |
| 5,000 km/h | 4.0815 Ma | kilometres per hour to Mach (sea level, 15 °C) |
Units in this converter and their exact factors
| Unit | Symbol | One unit in metre per seconds |
|---|---|---|
| metre per second | m/s | 1 metre per second |
| kilometre per hour | km/h | 0.2777777778 metre per second |
| mile per hour | mph | 0.44704 metre per second |
| knot | kn | 0.5144444444 metre per second |
| foot per second | ft/s | 0.3048 metre per second |
| Mach (sea level, 15 °C) | Ma | 340.29 metre per second |
FAQFrequently asked questions about speed conversion
What is 1,000 km/h in Mach?
About Mach 0.82 at sea level.
Why does altitude matter?
The speed of sound depends on temperature, and temperature falls with altitude — so the same true airspeed is a higher Mach number up high.
What Mach is an airliner?
Around 0.78 to 0.85 in cruise.
What is the sound barrier?
Mach 1 — 1,225 km/h at sea level.
Is Mach a speed?
No, a ratio. It is speed divided by the local speed of sound.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Physical Laboratory (NPL) — United Kingdom's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.