How do I convert km/h to m/s in my head?

Divide by 3.6. 90 km/h is 25 m/s. The factor is exact because a kilometre is 1,000 m and an hour is 3,600 s.

One nautical mile per hour, so 1.852 km/h exactly. It survives in navigation because a knot is one minute of latitude per hour, which makes chart work arithmetic rather than conversion.

Conversionsmeasurement

Speed Converter

Speed between kilometres per hour, miles per hour, metres per second and knots. A knot is one nautical mile an hour, and a nautical mile is a minute of latitude, which is why it is not a round number in either system.

Also called: kmh to mph, mps to kmh, knots converter.

Result

0.621371

1 Kilometres per hour is 0.621371 Miles per hour. The factor is 0.6213711922, and the inverse is 1.609344. The table below gives the same value in every speed unit at once.

Conversion factor

0.6213711922

Inverse factor

1.609344

Value in mps

0.2777777778

Converting from

Kilometres per hour

Converting to

Miles per hour

Dimension

speed

How this is calculated

The same value in every speed unit

Unit	Value
Metres per second	0.28
Kilometres per hour	1
Miles per hour	0.62
Knot	0.54
Feet per second	0.91

Method and background

How this is calculated

All held against metres per second. The knot survives in aviation and at sea because a nautical mile is one minute of arc along a meridian, so a speed in knots converts directly into degrees of latitude covered per hour. That geometric convenience is worth more at sea than a round metric factor.

result = value * factor_from / factor_to

k: Each unit's size in mps

Worked examples

Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.

100 km/h in mph

Value: 100
From: Kilometres per hour
To: Miles per hour

Result62.137119

100 / 1.609344, exact by the international mile

Open this example

a knot in km/h

Value: 1
From: Knot
To: Kilometres per hour

Result1.852

exact: a nautical mile is defined as 1852 metres

Open this example

zero is zero in any unit

Value: 0
From: Miles per hour
To: Metres per second

Result0

degenerate case

Open this example

Frequently asked questions

How do I convert km/h to m/s in my head?: Divide by 3.6. 90 km/h is 25 m/s. The factor is exact because a kilometre is 1,000 m and an hour is 3,600 s.
What is a knot?: One nautical mile per hour, so 1.852 km/h exactly. It survives in navigation because a knot is one minute of latitude per hour, which makes chart work arithmetic rather than conversion.