Speed Converter
Convert between 9 units of speed and velocity — common, nautical, and scientific.
What is Speed?
Speed is the rate of change of distance over time — how far something moves per second, hour, or any other time interval. It's a scalar (magnitude only); velocity adds a direction. The SI unit is metres per second (m/s), but real-world speed is measured in many systems by convention: km/h on roads in most of the world, mph in the US and UK, knots at sea and in the cockpit (one nautical mile per hour), Mach numbers for supersonic flight (multiples of the local speed of sound), and the speed of light c (299,792,458 m/s exactly) for relativistic physics. Converting between systems is a one-line factor — but get the factor right: 1 mph = 1.609344 km/h exactly. This Speed Converter handles 9 units at once. Need related units? Use the Length Converter for distance or the Temperature Converter for the conditions that affect Mach.
From
Kilometers per Hour (km/h)
To
Miles per Hour (mph)
Result
0.6213717mph
1 km/h = 0.6213717 mph
Formula: 1 km/h x 0.277778 / 0.44704 = 0.6213717 mph
Popular Conversions
| From | To |
|---|---|
| 1 km/h | 0.621371 mph |
| 1 mph | 1.60934 km/h |
| 1 m/s | 3.6 km/h |
| 1 knot | 1.852 km/h |
| 1 m/s | 2.23694 mph |
| Mach 1 | 1234.8 km/h |
Speed References
Walking~5 km/h
City driving~50 km/h
Highway~120 km/h
Commercial jet~900 km/h
Speed of sound1234.8 km/h
How to use this tool
- 1Type a value into any unit fieldEnter your number in the unit you have — m/s, km/h, mph, knots, anything.
- 2Read the live conversionsAll 8 other unit fields update instantly with the equivalent speed.
- 3Copy the value you needClick the copy icon next to any field to grab the converted number.