kilometre per hour
Unit whose name includes an SI unit and a non-SI unit accepted for use with SI
Name | Symbol | Quantity | Value in SI units | |
kilometre per hour | km/h | speed | 1000⁄3600 m s−1 | ![]() |
DefinitionThe kilometre per hour, symbol km/h, is a non-SI unit of speed, accepted for use with the SI. |
The kilometre per hour is derived from the metre (an SI base unit) and the hour (a non-SI unit accepted for use with the SI).
Distance | ÷ Time | = Speed | Expressed in SI units |
1 km | ÷ 1 h | = 1 km/h | = 1000⁄3600 m s-1 |
3.6 km | ÷ 1 h | = 3.6 km/h | = 3600⁄3600 m s-1 |
3600 m | ÷ 3600 s | = 3600⁄3600 m s-1 | = 1 m s-1 |
A speed of 3.6 km/h is equal to 1 m s-1.
The kilometre per hour is the unit of speed used on road signs and motor vehicle speedometers in most countries of the world.
90 km/h = 25 m s-1
Examples of motor vehicle speeds
Expressed in km/h | Expressed in SI base units |
18 km/h | 5 m s-1 |
36 km/h | 10 m s-1 |
54 km/h | 15 m s-1 |
72 km/h | 20 m s-1 |
90 km/h | 25 m s-1 |
108 km/h | 30 m s-1 |
Usage
Abreviations, such as kph and kmph, should not be used in place of the symbol km/h.