Formula

km/hour to m/second

Arithmetic • Time, Speed and Distance

Formula

1 km/hour = \frac{5}{18} m/second

Since

1

= 1000

m and

1

hour

= 3600

s, a speed in km/hour becomes a speed in m/second on multiplying by

\frac{5}{18}

, and a speed in m/second becomes km/hour on multiplying by

\frac{18}{5}

How to use it

1Multiply by $\frac{5}{18}$ going from km/hour to m/second, and by $\frac{18}{5}$ coming back.
2Convert before combining two speeds, so that a relative speed is formed in one unit throughout.
3Match the unit to the time given: a time in seconds means the speed belongs in m/second.

Express

72

km/hour in metres per second.

Step-by-step

1
$72 \times \frac{5}{18}$
Why: Multiply by $\frac{5}{18}$ to turn km/hour into m/second.
2
$= 20$

Answer

20

m/second

Watch out

The two factors are reciprocals and are easy to interchange. The sanity check is that the figure in m/second is always the smaller of the two.

Also known as

km/h to m/s, 5/18 factor, speed unit conversion, metres per second