Last updated: 3 October 2026
Reviewed by Jordan Morley, FA Level 2 Football Coach
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.
Worked examples
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Why this conversion matters
Speed limits, broadcast speed-gun readings and cycling/motorsport commentary mix km/h and mph depending on the country — UK and US sport commentary defaults to mph, while the rest of the world (and all metric-system race data) uses km/h.
FAQ
Why do UK and US sports commentary use mph while most of the world uses km/h?
Both countries retain the imperial system for everyday speed measurement by long-standing convention, even though most international sporting bodies and metric countries use km/h.
What's a fast cycling descent speed in mph?
Elite cyclists exceed 50-60 mph (80-97 km/h) on steep mountain descents in races like the Tour de France — recreational riders rarely reach these speeds safely.
Is a radar gun reading in mph or km/h more accurate?
Neither is more accurate — a radar gun measures the same physical speed regardless of the unit it displays; mph and km/h are simply different ways of expressing an identical value.