How to convert miles per hour to kilometres per hour
One mile per hour equals 1.6093 kilometres per hour, so multiply the number of miles per hour by 1.6093:
km/h = mph × 1.6093
mph = km/h ÷ 1.6093 (1 km/h = 0.621371 mph)
Example: 20 mph → 20 × 1.6093 = 32.1869 km/h.
Going the other way, divide by 1.6093, or multiply by 0.621371; the kilometres per hour to miles per hour converter does it for you.
Everyday values
| Miles per hour | Kilometres per hour | For example |
|---|---|---|
| 20 mph | 32.1869 km/h | a residential zone in the UK |
| 30 mph | 48.2803 km/h | a typical UK urban limit |
| 55 mph | 88.5139 km/h | a US highway limit in some states |
| 65 mph | 104.607 km/h | a common US highway limit |
| 70 mph | 112.654 km/h | the UK motorway limit |
When you need this conversion
The UK and the US post speed limits in mph. The UK motorway limit of 70 mph is about 113 km/h; common US highway limits of 65–70 mph are 105–113 km/h. Multiplying by 1.6 gives a fast mental estimate.
Mile per hour to kilometre per hour conversion table
| mph | km/h | mph | km/h |
|---|---|---|---|
| 10 mph | 16.0934 km/h | 50 mph | 80.4672 km/h |
| 15 mph | 24.1402 km/h | 55 mph | 88.5139 km/h |
| 20 mph | 32.1869 km/h | 60 mph | 96.5606 km/h |
| 25 mph | 40.2336 km/h | 65 mph | 104.607 km/h |
| 30 mph | 48.2803 km/h | 70 mph | 112.654 km/h |
| 35 mph | 56.327 km/h | 75 mph | 120.701 km/h |
| 40 mph | 64.3738 km/h | 80 mph | 128.748 km/h |
| 45 mph | 72.4205 km/h |
About the units
- Mile per hour (mph): 1 mile per hour, exactly 1.609344 km/h.
- Kilometre per hour (km/h): 1,000 metres per 3,600 seconds.
Both are units of speed. The conversion factor comes from the exact definitions above, so the calculator is exact; results are only rounded for display (up to six significant digits).
Frequently asked questions
How many kilometres per hour are in one mile per hour?
One mile per hour is 1.6093 kilometres per hour. One kilometre per hour is 0.621371 miles per hour.
How do I convert miles per hour to kilometres per hour?
Multiply the value in miles per hour by 1.6093. To go back, divide by 1.6093.
What is 20 mph in kilometres per hour?
20 mph = 32.1869 km/h.
What is 30 mph in kilometres per hour?
30 mph = 48.2803 km/h.
Sources
- NIST Special Publication 811 (2008), Guide for the Use of the International System of Units (SI), Appendix B: conversion factors.
- NIST Handbook 44 (2024), Appendix C: General tables of units of measurement.
Last reviewed 5 October 2026. Results are estimates; see our disclaimer.