How the Speed Converter Works
This tool instantly converts between the main speed units used in road, nautical, aeronautical, and scientific contexts.
Supported Speed Units
- km/h (kilometers per hour): standard in most of the world for road speed
- mph (miles per hour): used in the US and UK for speed limits
- m/s (meters per second): SI unit of speed, used in physics and engineering
- knots (kn): international standard for maritime and aviation navigation. 1 knot = 1 nautical mile/hour
- ft/s (feet per second): used in ballistics and engineering
- Mach: ratio of object speed to speed of sound. Mach 1 = 343 m/s at 20 degrees C
Key Conversion Factors
| From | To | Factor |
|---|---|---|
| 1 km/h | mph | 0.6214 |
| 1 mph | km/h | 1.6093 |
| 1 m/s | km/h | 3.6000 |
| 1 knot | km/h | 1.8520 |
| Mach 1 | km/h | 1,235.0 |
Speed of Sound and Mach Number
Mach 1 corresponds to about 343 m/s (1,235 km/h or 767 mph) in air at 20 degrees C at sea level, per the ICAO Standard Atmosphere. The speed of sound varies with temperature: at cruising altitude (about -50 degrees C) it drops to about 295 m/s (660 mph).