Avoid rounding before the final display
Early rounding can noticeably shift high-speed conversions; retain the full 1.609344 factor internally.
Unit converter
MPH to KM/H Converter
Convert miles per hour to kilometres per hour instantly. Miles per hour for road speeds. See the formula, worked examples and practical reference values.
How to convert mph to km/h
Miles per hour to kilometres per hour is useful for comparing speed limits, vehicle specifications and journey speeds in countries using metric units.
Formula: km/h = mph × 1.609344
Reverse formula: mph = km/h × 0.621371
Worked example
1 mph = 1.609344 km/h
- = 0.44704 m/s
- = 0.868976 kn
Avoid these errors
Common mistakes
Road-sign limits are jurisdiction-specific
A converted reference does not replace the posted legal limit or local driving rules.
Useful for: Road, vehicle and travel speeds converted to kilometres per hour.
Common mph to km/h conversions
| miles per hour | kilometres per hour |
|---|---|
| 1 mph | 1.609344 km/h |
| 5 mph | 8.04672 km/h |
| 10 mph | 16.09344 km/h |
| 20 mph | 32.18688 km/h |
| 30 mph | 48.28032 km/h |
| 40 mph | 64.37376 km/h |
| 50 mph | 80.4672 km/h |
| 60 mph | 96.56064 km/h |
| 70 mph | 112.65408 km/h |
| 100 mph | 160.9344 km/h |
About the units
A mile per hour is an imperial unit represented by mph. A kilometre per hour is a metric unit represented by km/h. Calculations use the same authoritative registry as the full speed converter, retaining full precision until display.
Sources and definitions
NIST — SI units and conversion guidance
Conversion constants come from the shared EzyCalculator unit registry. See how calculations are reviewed and tested.