To convert miles per hour to kilometres per hour, multiply by 1.609344. To go the other way, divide. So 70 mph is 70 × 1.609344 = about 112.7 km/h. The speed converter does it instantly and covers m/s and knots too.
That is the rule. Here is the shortcut and the speed-limit equivalents that are handy abroad.
Why the factor is 1.609344
A mile is exactly 1.609344 kilometres, so a speed in miles per hour converts to kilometres per hour using the same number. It is the same factor as converting miles to kilometres, just applied to “per hour”. Because the mile is exactly defined, the conversion is exact and only rounded for display.
How to convert mph to km/h
mph to km/h
Multiply by 1.609344.
- 30 mph → 48.3 km/h
- 60 mph → 96.6 km/h
- 70 mph → 112.7 km/h
km/h to mph
Divide by 1.609344.
- 50 km/h → 31.1 mph
- 100 km/h → 62.1 mph
- 130 km/h → 80.8 mph
The speed converter handles both directions.
A quick mental shortcut
Multiply mph by 1.6 in your head, or add about 60 percent. So 50 mph is roughly 80 km/h, and 70 mph is about 112. For km/h to mph, divide by 1.6, or take 60 percent. These are close enough to read a speedometer or a sign at a glance.
Speed limits worth knowing abroad
If you drive in another country, a few equivalents save constant mental maths:
- 30 mph ≈ 48 km/h, a typical town limit.
- 50 km/h ≈ 31 mph, the common metric town limit.
- 60 mph ≈ 97 km/h and 70 mph ≈ 113 km/h, UK and US highway speeds.
- 100 km/h ≈ 62 mph and 130 km/h ≈ 81 mph, common motorway limits in Europe.
Hire cars usually show the speedometer in the local unit, so knowing these stops you misreading a sign. For temperatures abroad, see the temperature converter.