How to Convert Miles per hour to Kilometres per hour (mph to km/h)
Speed conversions come up with expressway limits in km/h, foreign car specs in mph and wind speeds reported in knots by the Meteorological Service. This guide shows how to convert miles per hour into kilometres per hour by hand, with examples and a quick-reference table.
The conversion
To convert miles per hour to kilometres per hour, multiply the value by 1.609344. To go the other way, divide by the same number (or multiply by 0.6213711922). For a quick estimate, multiply by about 1.6.
Kilometres per hour = miles per hour × 1.609344
Worked examples
- 3 mph = 4.828 km/h
- 12.5 mph = 20.1168 km/h
- 75 mph = 120.7008 km/h
Miles per hour to Kilometres per hour table
| Miles per hour | Kilometres per hour |
|---|---|
| 1 mph | 1.6093 km/h |
| 2 mph | 3.2187 km/h |
| 5 mph | 8.0467 km/h |
| 10 mph | 16.0934 km/h |
| 20 mph | 32.1869 km/h |
| 25 mph | 40.2336 km/h |
| 50 mph | 80.4672 km/h |
| 100 mph | 160.9344 km/h |
| 250 mph | 402.336 km/h |
| 500 mph | 804.672 km/h |
| 1,000 mph | 1,609.34 km/h |
Common questions
Is mph to km/h exact?
The factors used here are the internationally defined values where they exist; results are rounded for display only.
How do I convert back?
Use the Kilometres per hour to Miles per hour converter.
Mistakes to avoid
Multiplying when you should divide
Converting to a smaller unit gives a bigger number, and converting to a larger unit gives a smaller one. If your answer moves the wrong way, you have inverted the factor.
Dropping the units
A bare number without a unit is easy to misread later. Always write the unit with the result.
Rounding the factor too early
Using 3 instead of 3.28 for feet per metre introduces an error of almost 9% before you have started.
Background
Writing the units next to every number while you work is the simplest way to avoid mistakes. If the units do not cancel to leave the one you want, the calculation is set up wrongly.
A conversion table is handy for common values, but a calculator is faster and avoids interpolation errors for anything in between.
Singapore adopted the metric system in the 1970s, replacing imperial units and traditional Chinese measures in most official uses. Metric units are now standard in schools, trade and government, but older units survive in property, markets and imported goods.
For any value, use the Miles per hour to Kilometres per hour Converter or browse all speed converters.
Run your own numbers: Miles per hour to Kilometres per hour Converter