km/h to Mach Converter
Convert kilometers per hour to Mach number, at the sea-level speed of sound. Results update as you type; exact factors shown.
One kilometer 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 meters 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 US uses customary units (US gallon, short ton, °F) in daily life; NIST SP 811 gives the exact SI factors.
Common speed conversions
| From | To | Units |
|---|---|---|
| 100 km/h | 0.0816 Ma | kilometer per hour to Mach (sea level, 15 °C) |
| 300 km/h | 0.2449 Ma | kilometer per hour to Mach (sea level, 15 °C) |
| 500 km/h | 0.4081 Ma | kilometer per hour to Mach (sea level, 15 °C) |
| 800 km/h | 0.653 Ma | kilometer per hour to Mach (sea level, 15 °C) |
| 900 km/h | 0.7347 Ma | kilometer per hour to Mach (sea level, 15 °C) |
| 1,000 km/h | 0.8163 Ma | kilometer per hour to Mach (sea level, 15 °C) |
| 1,225 km/h | 1 Ma | kilometer per hour to Mach (sea level, 15 °C) |
| 1,500 km/h | 1.2244 Ma | kilometer per hour to Mach (sea level, 15 °C) |
| 2,000 km/h | 1.6326 Ma | kilometer per hour to Mach (sea level, 15 °C) |
| 2,500 km/h | 2.0407 Ma | kilometer per hour to Mach (sea level, 15 °C) |
| 3,000 km/h | 2.4489 Ma | kilometer per hour to Mach (sea level, 15 °C) |
| 5,000 km/h | 4.0815 Ma | kilometer per hour to Mach (sea level, 15 °C) |
Units in this converter and their exact factors
| Unit | Symbol | One unit in meter per seconds |
|---|---|---|
| meter per second | m/s | 1 meter per second |
| kilometer per hour | km/h | 0.2777777778 meter per second |
| mile per hour | mph | 0.44704 meter per second |
| knot | kn | 0.5144444444 meter per second |
| foot per second | ft/s | 0.3048 meter per second |
| Mach (sea level, 15 °C) | Ma | 340.29 meter 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 Institute of Standards and Technology (NIST) — United States's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.