Speed Converter
Convert speed between km/h, m/s, mph and knots — see all four units at once.
How to use the speed converter
- Enter the speed value.
- Choose the unit you're converting from and to.
- All four units update automatically as you type.
Common speed units
Kilometers per hour (km/h) is the standard road-speed unit in most of the world. Meters per second (m/s) is the SI unit, used in physics and engineering. Miles per hour (mph) is used for road speeds in the US and UK. Knots (nautical miles per hour) are used in aviation and maritime navigation, where 1 knot equals exactly 1.852 km/h.
Worked example: 100 km/h is 100 ÷ 3.6 = 27.78 m/s. The factor 3.6 comes from an hour being 3,600 seconds and a kilometre being 1,000 metres. The same speed is 100 ÷ 1.609344 = 62.14 mph and 100 ÷ 1.852 = 54.00 knots. That 100 km/h lands on almost exactly 54 knots is a coincidence worth noting, given that a nautical mile is defined as one arcminute of the earth's circumference.
Frequently asked questions
How do I convert km/h to m/s?
Divide by 3.6 — for example 100 km/h ÷ 3.6 ≈ 27.78 m/s. This works because there are 3,600 seconds in an hour and 1,000 meters in a kilometer.
What exactly is a knot?
A knot is one nautical mile per hour, defined as exactly 1.852 km/h. It's used in aviation, shipping and meteorology because a nautical mile is directly tied to a minute of latitude on the globe, which is convenient for navigation.
Why do aviation and maritime navigation use knots instead of km/h or mph?
Because a nautical mile corresponds to one minute of arc of latitude, distances measured on nautical charts (which use latitude/longitude) translate directly into speed and distance without extra conversion — a major practical advantage for navigation.