Miles per Hour to Kilometers per Hour
Convert miles per hour (mph) to kilometers per hour (km/h). Both measure velocity, and the conversion comes up in driving, aviation, sports work.
The Formula
``
kilometers per hour = miles per hour × 1.609344
miles per hour = kilometers per hour × 0.621371192237
`
One miles per hour is 1.6093 kilometers per hour, and one kilometers per hour is 0.621371 miles per hour.
Conversion Table
| Miles per Hour | Kilometers 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 |
| 25 mph | 40.2336 km/h |
| 50 mph | 80.4672 km/h |
| 100 mph | 160.9344 km/h |
| 500 mph | 804.672 km/h |
| 1,000 mph | 1,609.34 km/h |
The Other Direction
| Kilometers per Hour | Miles per Hour |
|---|---|
| 1 km/h | 0.621371 mph |
| 2 km/h | 1.2427 mph |
| 5 km/h | 3.1069 mph |
| 10 km/h | 6.2137 mph |
| 25 km/h | 15.5343 mph |
| 50 km/h | 31.0686 mph |
| 100 km/h | 62.1371 mph |
| 500 km/h | 310.6856 mph |
| 1,000 km/h | 621.3712 mph |
What Each Unit Is
Miles per Hour (mph) — miles travelled per hour, equal to 1.609344 km/h exactly. The road-speed unit of the US and UK.
Kilometers per Hour (km/h) — kilometres travelled per hour, equal to 1/3.6 m/s. The road-speed unit in almost every country outside the US and UK.
A Sense of Scale
Residential limits are 25–30 mph- US freeways are 65–75 mph
- A jog is 6 mph
- Urban limits are 30–50 km/h
- Motorways are 100–130 km/h
- A cyclist cruises at 20 km/h
Doing It in Your Head
Multiply by 8, then divide by 5. That is off by 0.58% — close enough to judge a
distance, a weight or a price, and not close enough to sign off on a drawing.
Exact Mental shortcut 16.0934 km/h 16 km/h 160.9344 km/h 160 km/h
Precision
The factor 1.609344 is rounded. For engineering work carry more digits than the table above, and round only at the end — rounding at each step compounds.
In Code
`javascript
const milePerHourToKilometerPerHour = (value) => value * 1.609344;
``
Where This Conversion Comes Up
- Driving
- Aviation
- Sports
- Shipping
- Weather
How Many Decimals Do You Need?
Rounding the factor costs accuracy, and how much depends on the factor. Converting 137 mph with the factor truncated at each decimal place:
| Decimals kept | Factor | 137 mph becomes | Error |
|---|---|---|---|
| 0 | 2 | 274 | 24.2742% |
| 1 | 1.6 | 219.2 | 0.5806% |
| 2 | 1.61 | 220.57 | 0.0408% |
| 3 | 1.609 | 220.433 | 0.0214% |
| 4 | 1.6093 | 220.474 | 0.0027% |
The right number of significant figures is set by your input, not by the converter. If you measured miles per hour to three significant figures, the answer in kilometers per hour is only good to three — writing more digits claims precision the measurement never had.