Miles Per Hour to Kilometers Per Hour
An instant miles per hour-to-kilometers per hour converter, with the formula and a reference table below.
| Miles Per Hour | Kilometers Per Hour |
|---|---|
| 1 mph | 1.609344 km/h |
| 2 mph | 3.218688 km/h |
| 3 mph | 4.828032 km/h |
| 5 mph | 8.04672 km/h |
| 10 mph | 16.09344 km/h |
| 25 mph | 40.2336 km/h |
| 50 mph | 80.4672 km/h |
| 100 mph | 160.9344 km/h |
How to use
- Enter a value in the Miles Per Hour field.
- The Kilometers Per Hour figure appears immediately — no button to press.
- Typing in the Kilometers Per Hour field converts back to Miles Per Hour the same way.
- Use the reference table for the values that come up most often.
Miles Per Hour to Kilometers Per Hour formula
The factor from miles per hour to kilometers per hour is 1.609344.
km/h = mph × 1.609344
Why this factor: the mile per hour and the kilometer per hour are both defined against the meter per second, so dividing one definition by the other gives 1.609344 directly. Both definitions are set out in full below.
To go the other way, divide by 1.609344 — or use the Kilometers Per Hour to Miles Per Hour converter, which is the same calculation reversed.
Worked example
Take 100 mph and multiply by the factor 1.609344: the result is 160.9344 km/h.
100 mph × 1.609344 = 160.9344 km/h
The converter above does this for any value you type, in either direction.
What is a mile per hour?
Miles per hour is the road speed unit of the United States and the United Kingdom.
Definition: Exactly 0.44704 meters per second, following from the exact 1,609.344 m mile.
Where it is used: US and UK speed limits and speedometers, plus baseball pitch and tennis serve speeds.
What is a kilometer per hour?
Kilometers per hour is the everyday speed unit for road traffic in most of the world.
Definition: Exactly 1,000 meters per 3,600 seconds, so 1 km/h is exactly 1/3.6 m/s.
Where it is used: Speed limits, vehicle speedometers, and weather wind speeds outside the US and UK.
Worth knowing: A handy shortcut: divide km/h by 3.6 for m/s, or multiply m/s by 3.6 to go the other way.
Miles Per Hour vs Kilometers Per Hour
The mile per hour is an imperial unit while the kilometer per hour is a metric unit. That is why the factor between them is not a round number: the two systems were defined independently and only later tied together by exact agreement.
Frequently asked questions
How many kilometers per hour are in a mile per hour?
One mile per hour equals 1.609344 kilometers per hour.
What is the formula to convert miles per hour to kilometers per hour?
Multiply the number of miles per hour by 1.609344. To reverse it, divide by 1.609344 instead.
How do I convert kilometers per hour back to miles per hour?
Divide by 1.609344, which is the same as multiplying by 0.621371192.
How many kilometers per hour are in 10 miles per hour?
10 mph works out to 16.09344 km/h.
Is there anything to watch out for with kilometers per hour?
A handy shortcut: divide km/h by 3.6 for m/s, or multiply m/s by 3.6 to go the other way.
How is the mile per hour defined?
Exactly 0.44704 meters per second, following from the exact 1,609.344 m mile.