The exact equivalent
A kilometre is 0.621371 miles. A mile is 1,609.344 metres exactly, since the yard is defined as 0.9144 m.
1 km = 0.62137119 mi
1 mi = 1.609344 km
How to convert it by hand
Just multiply by the conversion factor. To go from kilometres to miles, multiply by 0.621371; to come back, divide by that same number or multiply by 1.609344.
For example: 25 km × 0.621371 = 15.5343 mi.
A tip that saves mistakes: check the result goes the way you expect. If miles are a smaller unit than kilometres, the number has to come out bigger. If it comes out smaller, you divided when you should have multiplied.
Conversion table
| km | mi |
|---|---|
| 1 | 0.6214 |
| 2 | 1.2427 |
| 5 | 3.1069 |
| 10 | 6.2137 |
| 20 | 12.4274 |
| 50 | 31.0686 |
| 100 | 62.1371 |
Reference points to picture it
| Reference | Equals |
|---|---|
| A 5 km run | 3.11 miles |
| A marathon | 42.195 km = 26.22 miles |
| A 100 km/h speed limit | 62 mph |
| London to Paris | 344 km = 214 miles |
The trick for doing it in your head
Multiply by 6 and drop a digit. For 80 km: 80 × 6 = 480, so about 48 miles, against a true 49.7. Or use the Fibonacci trick: consecutive Fibonacci numbers are almost exactly km and miles, so 8 km ≈ 5 miles and 13 km ≈ 8 miles.
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.