1 mile per hour = 1.609 kilometers per hour
Convert miles per hour to kilometers per hour with an exact, internationally defined factor — 1 mph = 0.44704 m/s (exact).
miles per hour to kilometers per hour
Computed with the exact factor · NIST SP 811
| Mile per hour | Kilometer per hour |
|---|---|
| 0.5 mph | 0.8047 km/h |
| 1 mph | 1.609 km/h |
| 2 mph | 3.219 km/h |
| 3 mph | 4.828 km/h |
| 5 mph | 8.047 km/h |
| 10 mph | 16.09 km/h |
| 25 mph | 40.23 km/h |
| 50 mph | 80.47 km/h |
| 100 mph | 160.93 km/h |
Exact factor details
- Exact factor
- 1 mph = 1.609 km/h (exact definition)
- Significant digits
- up to 4 significant digits shown
- Data source
- NIST SP 811 — verified against official tables
Why mph to km/h trips people up
Speed conversions between kilometers per hour, miles per hour, and meters per second. Because the mile is exactly 1,609.344 meters, the km/h ↔ mph factor is exact: 1 mph = 1.609344 km/h. Miles per hour remains the road speed unit in the US and UK. Kilometers per hour is the standard road speed unit outside the US and UK.
Speed limits, treadmill displays, and weather reports mix these units constantly. A quick sanity check: 100 km/h is about 62 mph, and highway speeds of 120 km/h are about 75 mph. Runners more often need pace (minutes per kilometer) rather than speed — see the pace calculator for that.
Use the quick-reference table for the amounts people actually look up, and the converter above for everything in between. Both are computed from the same factor at full precision, so the table and the converter can never disagree — there is no second, rounded copy of the data anywhere on this page.
Frequently asked questions
Is the mph to km/h conversion exact?
Yes. 1 mph = 0.44704 m/s (exact) and 1 km/h = 1/3.6 m/s (exact) are exact definitions, so the conversion is exact — results are rounded only for readability.
How do I convert mph to km/h in my head?
Multiply km/h by 0.62 (or miles per hour by 1.6) for a close estimate.
Why do other sites show slightly different mph to km/h results?
They round at different steps. This page computes with the full-precision factor and rounds only the final displayed number, so small trailing digits can differ from sites that round earlier.