Convert km/h → mph
About this conversion
One kilometre per hour equals exactly 0.621371 miles per hour. The conversion comes from the definition of a mile: 1 mile = 1.60934 km, so 1 km = 1 ÷ 1.60934 = 0.621371 miles.
This converter is useful for cyclists checking Strava speeds on mixed-unit routes, runners using overseas race results, treadmill users with metric displays, and anyone comparing international speed records where one country reports in km/h and another in mph.
Frequently asked questions
What is the formula to convert km/h to mph?
Multiply the km/h value by 0.621371. For a quick mental approximation, multiply by 0.6 (or multiply by 3 and divide by 5). Example: 50 km/h × 0.621371 = 31.07 mph. Quick estimate: 50 × 0.6 = 30 mph.
How do I convert mph back to km/h?
Divide by 0.621371, or multiply by 1.60934. Example: 60 mph × 1.60934 = 96.56 km/h. Quick mental check: 60 mph is roughly 100 km/h (the actual figure is 96.6 km/h).
Why do the UK and US still use mph instead of km/h?
Both countries retained the imperial system for road speed after metrication was adopted elsewhere. The UK metricated most measurements in the 1970s but kept mph for road signs and speed limits due to the cost of replacing signage and public resistance to change. The US has never formally metricated. Most other countries, including all of Europe, use km/h for road speeds.
What is 100 km/h in mph?
100 km/h = 62.14 mph. This is a useful reference because 100 km/h is a common motorway speed limit in Europe, and 62 mph is close to the 60 mph national speed limit on UK single carriageways. The UK motorway limit of 70 mph = 112.7 km/h.