The exact equivalent
Divide by 3.6. It comes from 1,000 metres per kilometre divided by 3,600 seconds per hour.
1 km/h = 0.27777778 m/s
1 m/s = 3.6 km/h
How to convert it by hand
Just multiply by the conversion factor. To go from kilometres per hour to metres per second, multiply by 0.277778; to come back, divide by that same number or multiply by 3.6.
For example: 25 km/h × 0.277778 = 6.9444 m/s.
A tip that saves mistakes: check the result goes the way you expect. If metres per second are a smaller unit than kilometres per hour, the number has to come out bigger. If it comes out smaller, you divided when you should have multiplied.
Conversion table
| km/h | m/s |
|---|---|
| 1 | 0.2778 |
| 2 | 0.5556 |
| 5 | 1.3889 |
| 10 | 2.7778 |
| 20 | 5.5556 |
| 50 | 13.8889 |
| 100 | 27.7778 |
Reference points to picture it
| Reference | Equals |
|---|---|
| A motorway speed | 120 km/h = 33.3 m/s |
| A city speed | 50 km/h = 13.9 m/s |
| A walking pace | 5 km/h = 1.4 m/s |
| A strong gale | 75 km/h = 20.8 m/s |
The trick for doing it in your head
Divide by 3.6, or for a rough version divide by 4 and add 10%. For 100 km/h: 25 plus 2.5 gives 27.5 m/s, against a true 27.8.
It is fine for getting by without a phone, but not for anything that depends on precision: in a recipe, on a building site or in a dose, use the exact conversion.