Convert speed and velocity between km/h, mph, m/s, ft/s, knots and Mach.
How to use the Speed Converter
- Enter a value.
- Choose the unit you are converting from.
- See the equivalent in every other unit.
Common speed conversions
1 mph = 1.609344 km/h. 1 m/s = 3.6 km/h. 1 knot = 1.852 km/h (one nautical mile per hour). Mach 1 is taken as 343 m/s, the speed of sound in dry air at 20 °C.
Frequently asked questions
How do I convert km/h to mph?
Multiply by 0.621371.
Why is Mach approximate?
The speed of sound depends on air temperature, so Mach 1 varies with altitude.