Converters Miles per hour to kilometres per hour
Convert mph to km/h with the exact factor, plus a speed-limit chart for driving abroad and the mental arithmetic that gets you close.
1 mph = 1.609344 km/h
kilometres per hour = miles per hour × 1.609344
miles per hour to kilometres per hour
| mph | km/h |
|---|---|
| 1 | 1.609344 |
| 2 | 3.218688 |
| 3 | 4.828032 |
| 4 | 6.437376 |
| 5 | 8.04672 |
| 10 | 16.09344 |
| 15 | 24.14016 |
| 20 | 32.18688 |
| 25 | 40.2336 |
| 50 | 80.4672 |
| 75 | 120.7008 |
| 100 | 160.9344 |
| 500 | 804.672 |
| 1,000 | 1,609.344 |
One mile per hour is exactly 1.609344 kilometres per hour.
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Cite this page
Reembun. (2026, July 28). Miles per hour to kilometres per hour. https://reembun.com/convert/speed/mph-to-kmh
How to use it
Type the speed in mph
Kilometres per hour appear straight away, which is what a hire car dashboard abroad will be showing.
Go the other way
Swap units converts km/h back into mph.
Copy it or read the table
One mile per hour is exactly 1.609344 kilometres per hour. The table covers the usual speed limits.
The formula
km/h = mph × 1.609344
mph = km/h × 0.621371192Exact by definition. A statute mile is 1,760 yards, and a yard has been exactly 0.9144 metres since the International Yard and Pound Agreement of 1959, so a mile is exactly 1,609.344 metres.
Speed limits when driving abroad
| mph | km/h | Typically |
|---|---|---|
| 20 | 32 | Residential, school zone |
| 30 | 48 | UK urban roads (signed 50 in metric countries) |
| 40 | 64 | Urban arterial |
| 55 | 89 | US rural highway |
| 60 | 97 | UK single carriageway |
| 70 | 113 | UK motorway |
| 75 | 121 | US interstate |
| 80 | 129 | Some US western states |
Note the second row. A UK 30 mph limit is 48 km/h, but a metric country signs the equivalent urban limit as 50. Limits are set in round local numbers, not converted.
Common speeds
| Activity | mph | km/h |
|---|---|---|
| Brisk walk | 3.1 | 5 |
| Marathon world record pace | 12.9 | 20.8 |
| Cyclist, flat road | 15 | 24 |
| Usain Bolt, peak | 27.8 | 44.7 |
| Cheetah, sprint | 60 | 97 |
| Commercial jet, cruise | 560 | 900 |
Mental arithmetic
mph → km/h: multiply by 1.6. For 70 mph: 70 + 42 = 112 km/h. (True: 112.65)
km/h → mph: halve it, then add ten per cent of the result. For 100 km/h: 50 + 5 = 55, plus a bit more gives about 62 mph. (True: 62.14)
The Fibonacci shortcut works here as it does for distance, because consecutive Fibonacci numbers approximate the golden ratio of 1.618, which sits within 0.6% of the true factor of 1.609:
| mph | Fibonacci says | Actual |
|---|---|---|
| 30 | 50 km/h | 48.3 |
| 50 | 80 km/h | 80.5 |
| 80 | 130 km/h | 128.7 |
Why the US still uses mph
The United States formally adopted metric as its preferred system in 1975 but never made it mandatory, and road signage was one of the places customary units held. The UK is the notable hybrid: speeds and road distances in miles, almost everything else metric.
Aviation and shipping use knots worldwide regardless of the country, and altitude is reported in feet by ICAO convention, a mismatch that requires conversion tables in cockpits crossing into the handful of countries that use metres.
Common questions
What is the exact conversion factor?
One mile per hour is exactly 1.609344 kilometres per hour, following from the 1959 definition of the yard as exactly 0.9144 metres. Going the other way, one km/h is 0.621371192 mph. The same factor applies as for distance, because both are a distance divided by the same unit of time.
How do I convert while driving?
Multiply by 1.6, or use the Fibonacci trick: 50 mph is about 80 km/h, 80 mph is about 130 km/h. For the reverse, halve the km/h figure and add ten per cent, so 100 km/h becomes 50 plus 5 plus a little, around 62 mph. Both are close enough to keep you legal.
Are speed limits converted exactly?
No. Road signs use round numbers in whichever unit the country uses, so a 30 mph urban limit becomes 50 km/h across a border rather than 48. Never assume the limit converted precisely. Read the signs.
What is a knot?
One nautical mile per hour, which is 1.852 km/h exactly, or about 1.15 mph. It persists in aviation and shipping because a nautical mile is one minute of latitude, which makes navigation arithmetic straightforward in a way no metric unit matches.
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