KM/H to MPH Converter
Convert kilometres per hour to miles per hour — multiply by 0.6214. Results update as you type; exact factors shown.
One kilometre per hour is 0.6214 miles per hour — see the exact factor, not a rounded rule of thumb.
How the km/h to mph 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 km/h | 6.2137 mph | kilometres per hour to miles per hour |
| 20 km/h | 12.4274 mph | kilometres per hour to miles per hour |
| 30 km/h | 18.6411 mph | kilometres per hour to miles per hour |
| 40 km/h | 24.8548 mph | kilometres per hour to miles per hour |
| 50 km/h | 31.0686 mph | kilometres per hour to miles per hour |
| 60 km/h | 37.2823 mph | kilometres per hour to miles per hour |
| 80 km/h | 49.7097 mph | kilometres per hour to miles per hour |
| 90 km/h | 55.9234 mph | kilometres per hour to miles per hour |
| 100 km/h | 62.1371 mph | kilometres per hour to miles per hour |
| 110 km/h | 68.3508 mph | kilometres per hour to miles per hour |
| 120 km/h | 74.5645 mph | kilometres per hour to miles per hour |
| 130 km/h | 80.7783 mph | kilometres per hour to miles 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 100 km/h in mph?
62.1 mph.
What is a 50 km/h urban limit in mph?
31 mph, which is why UK towns post 30.
How do I estimate km/h to mph?
Take six-tenths: 80 km/h is about 48 mph, and exactly 49.7.
What is the fastest common speed limit?
130 km/h in much of Europe, which is 80.8 mph.
Does this work for wind speed?
Yes — the conversion is the same for any speed. Knots need the knots page.
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.