Speed Unit Converter (km/h, m/s, mph, knots)

Converts a speed into metres per second, kilometres per hour, metres per minute, miles per hour and knots. Dividing km/h by 3.6 gives m/s, since a kilometre is 1000 metres and an hour is 3600 seconds.

Explanation

Enter a speed and choose its unit, and every other unit follows. Kilometres per hour convert to metres per second exactly as easily as knots convert to km/h.

The definitions

Going from km/h to m/s means dividing by 3.6, because a kilometre is 1000 metres and an hour is 3600 seconds.

\text{m/s} = \dfrac{\text{km/h} \times 1000}{3600} = \dfrac{\text{km/h}}{3.6}

1 knot = 1 nautical mile per hour = 1.852 km/h exactly
1 mph = 1.609344 km/h

Example

Convert 72 km/h.

\dfrac{72}{3.6} = 20\ \text{m/s}

That is 1200 m/min, 44.74 mph, or 38.88 knots.

Worth memorising

36 km/h = 10 m/s
72 km/h = 20 m/s
108 km/h = 30 m/s

Multiply by 3.6 for km/h, divide by 3.6 for m/s. Physics problems come in m/s and daily life comes in km/h, so the trip between them is a frequent one.

Knots and nautical miles

A knot is one nautical mile per hour, the unit of choice for ships and aircraft. The nautical mile (1852 m) began life as the distance covered by one minute of latitude, which is why it remains so convenient on a chart.