Miles per hour to kilometers per hour
Type a value in miles per hour to see it in kilometers per hour straight away, or type in the second box to convert back.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Type the value in the miles per hour box.
- Read the result in kilometers per hour as you type, and pick the precision you need.
- Swap the direction to convert back, or copy the result.
How it is calculated
km/h = mph × 1.609344
Multiply the value in miles per hour by 1.609344 to get kilometers per hour.
Example
To convert 25 mph to kilometers per hour: 25 × 1.609344 = 40.2336 km/h.
Conversion table
| Miles per hour (mph) | Kilometers per hour (km/h) |
|---|---|
| 1 | 1.60934 |
| 2 | 3.21869 |
| 3 | 4.82803 |
| 5 | 8.04672 |
| 10 | 16.0934 |
| 20 | 32.1869 |
| 25 | 40.2336 |
| 50 | 80.4672 |
| 100 | 160.934 |
| 250 | 402.336 |
| 500 | 804.672 |
| 1,000 | 1,609.34 |
About the units
- Mile per hour
- Covering one international mile (1609.344 m) in one hour, exactly 0.44704 m/s. It is used on roads in the United States and the United Kingdom.
- Kilometer per hour
- Covering 1000 meters in 3600 seconds, so 1 km/h is exactly 1/3.6 m/s. It is the unit on road signs and car speedometers in most countries.
Limits and caveats
- Results are rounded for display and computed with the browser's floating point precision (about 15 significant digits).
- Both unit factors are exact by their official definitions.
Questions about this tool
How many kilometers per hour are in one mile per hour?
1 mph = 1.60934 km/h exactly.
How do I convert miles per hour to kilometers per hour?
Use km/h = mph × 1.609344. For example, 25 mph = 40.2336 km/h.
How many miles per hour are in one kilometer per hour?
1 km/h = 0.621371 mph.
How do I convert km/h to m/s in my head?
Divide by 3.6, because an hour is 3600 seconds and a kilometer is 1000 meters. For example 72 km/h is 20 m/s; multiply by 3.6 to go back.
Why do Mach values differ between sources?
The speed of sound depends on air temperature. We use 340.294 m/s at sea level and 15 °C; at 11 km altitude it is about 295 m/s, so Mach 1 is slower there.