kilometre per hour

Unit whose name includes an SI unit and a non-SI unit accepted for use with SI

Name	Symbol	Quantity	SI units
kilometre per hour	km/h	speed	1000⁄3600 m s-1
The kilometre per hour, symbol km/h, is a non-SI unit of speed, accepted for use with the SI.   One kilometre per hour is equal to 1000⁄3600 metres per second.
Definition			c

An object with a constant speed of one kilometre per hour moves a distance of one kilometre in one hour, or ¹⁰⁰⁰⁄₃₆₀₀ metres in one second.

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	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	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

Abbreviations, such as kph and kmph, should not be used in place of the symbol km/h.