Unit Conversion

Convert numbers between two units quickly and precisely

Speed

Unit Conversion

Convert speed units: km/h, m/s, mph, and knots

Speed is stated in different units internationally: kilometers per hour (km/h) as the European standard, meters per second (m/s) as the SI unit, miles per hour (mph) in the US and UK, and knots (kn) in shipping and aviation. You can also convert to multiples of the speed of light (c).

Key conversion factors:

  • 1 meter per second (m/s) = 3.6 kilometers per hour
  • 1 mile per hour (mph) = 1.609 kilometers per hour
  • 1 knot (kn) = 1.852 kilometers per hour – equal to one nautical mile per hour
  • Speed of light (c) = 299,792,458 meters per second – the physical speed limit

Applications:

  • Road traffic: converting speed limits between km/h and mph
  • Sports: running, cycling, and swimming speeds in km/h or m/s
  • Aviation & shipping: flight and wind speeds in knots
  • Physics: equations of motion in m/s and relativistic considerations near the speed of light

The speed converter makes it easy to compare speed limits, evaluate sports performance, and do nautical calculations. To calculate change of speed over time, use the acceleration converter.

Frequently asked questions about converting speed

You divide the km/h value by 3.6 to convert it to m/s (or multiply by 3.6 for the reverse). For example, 108 km/h equals exactly 30 m/s.

1 knot (kn) equals 1.852 km/h – exactly one nautical mile per hour. Knots are used worldwide as the standard unit of speed in shipping and aviation.

No, according to the laws of physics, no object with mass can move faster than the speed of light (299,792,458 m/s). The converter therefore prevents inputs that would mathematically exceed the speed of light.