mph to km/h formula
To convert miles per hour to kilometers per hour, multiply the number of miles per hour by 1.609344. In symbols: km/h = mph × 1.609344.
One mile per hour equals 1.609344 kilometers per hour, and one kilometer per hour equals 0.621371192237 miles per hour. A mile is exactly 1.609344 km, so 1 mph is exactly 1.609344 km/h.
Worked example
Suppose you have 65 miles per hour and need the answer in kilometers per hour.
- Write the formula: km/h = mph × 1.609344.
- Put in the number: 65 × 1.609344 = 104.60736.
- Round to suit the job. 104.6 km/h is accurate enough for most everyday uses.
So 65 mph is 104.60736 km/h. To check, convert back: 104.60736 km/h is 65 mph.
Common miles per hour to kilometers per hour values
| miles per hour (mph) | kilometers per hour (km/h) |
|---|---|
| 1 | 1.609344 |
| 2 | 3.218688 |
| 5 | 8.04672 |
| 10 | 16.09344 |
| 20 | 32.18688 |
| 50 | 80.4672 |
| 100 | 160.9344 |
Reference points
Some familiar amounts in miles per hour, converted to kilometers per hour:
- 25 mph, a school zone limit: 40.2336 km/h
- 65 mph, a US highway limit: 104.607 km/h
- 70 mph, a UK motorway limit: 112.654 km/h
- 120 mph, a fast train: 193.121 km/h
Where you will use it
US and UK speed limits, car reviews and weather wind reports are in mph, while most countries post limits in km/h. Drivers renting cars abroad and cyclists comparing speeds use this.
Quick mental math
Add 60 percent: 65 mph is 65 plus 39, about 104 km/h against the exact 104.6. Rule of thumb: multiply by 1.6. For 65 mph this gives 104 km/h against the exact 104.6, an error of 0.58 percent.
Going the other way
Need the reverse? Use the km/h to mph converter. For comparison, 1 km/h is 0.62137119 mph. To compare every speed unit at once, open the speed converter.
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