MPH to KM/H Converter
Convert miles per hour to kilometres per hour — multiply by 1.609. Results update as you type; exact factors shown.
One mile per hour is 1.6093 kilometres per hour — see the exact factor, not a rounded rule of thumb.
How the mph to km/h converter works
Speeds convert through metres per second. 1 km/h is 1000/3600 m/s; 1 mph is 1609.344/3600 m/s; a knot is one nautical mile (1,852 m) per hour. Mach is shown against the standard sea-level speed of sound of 340.29 m/s and varies with altitude and temperature.
The UK is metric for most trade and science but keeps miles, pints, stone and mpg (with the imperial gallon) in daily life.
Common speed conversions
| From | To | Units |
|---|---|---|
| 10 mph | 16.0934 km/h | miles per hour to kilometres per hour |
| 20 mph | 32.1869 km/h | miles per hour to kilometres per hour |
| 30 mph | 48.2803 km/h | miles per hour to kilometres per hour |
| 40 mph | 64.3738 km/h | miles per hour to kilometres per hour |
| 50 mph | 80.4672 km/h | miles per hour to kilometres per hour |
| 55 mph | 88.5139 km/h | miles per hour to kilometres per hour |
| 60 mph | 96.5606 km/h | miles per hour to kilometres per hour |
| 65 mph | 104.6074 km/h | miles per hour to kilometres per hour |
| 70 mph | 112.6541 km/h | miles per hour to kilometres per hour |
| 75 mph | 120.7008 km/h | miles per hour to kilometres per hour |
| 80 mph | 128.7475 km/h | miles per hour to kilometres per hour |
| 100 mph | 160.9344 km/h | miles per hour to kilometres per hour |
Units in this converter and their exact factors
| Unit | Symbol | One unit in metre per seconds |
|---|---|---|
| metre per second | m/s | 1 metre per second |
| kilometre per hour | km/h | 0.2777777778 metre per second |
| mile per hour | mph | 0.44704 metre per second |
| knot | kn | 0.5144444444 metre per second |
| foot per second | ft/s | 0.3048 metre per second |
| Mach (sea level, 15 °C) | Ma | 340.29 metre per second |
FAQFrequently asked questions about speed conversion
What is 70 mph in km/h?
112.7 km/h — the UK motorway limit.
What is 30 mph in km/h?
48.3 km/h.
How do I estimate mph to km/h?
Add half again and a bit: 60 mph → 90 + 6 = 96 km/h, and the exact answer is 96.6.
What is a US highway limit in km/h?
65 mph is 104.6 km/h; 75 mph is 120.7.
Is a knot the same as mph?
No — a knot is 1.151 mph, one nautical mile per hour.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Physical Laboratory (NPL) — United Kingdom's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.