Speed Converter
Convert km/h, mph, metres per second, knots and Mach — speed limits, wind speeds, running paces and aircraft speeds. 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 speed 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 |
|---|---|---|
| 100 km/h | 62.1371 mph | kilometres per hour to miles per hour |
| 60 mph | 96.5606 km/h | miles per hour to kilometres per hour |
| 1 kn | 1.852 km/h | knot to kilometres per hour |
| 1 m/s | 3.6 km/h | metre per second to kilometres per hour |
| 50 km/h | 31.0686 mph | kilometres per hour to miles per hour |
| 30 mph | 48.2803 km/h | miles per hour to kilometres per hour |
| 1 Ma | 1,225.044 km/h | Mach (sea level, 15 °C) to kilometres per hour |
| 10 m/s | 22.3694 mph | metres per second to miles per hour |
| 70 mph | 112.6541 km/h | miles per hour to kilometres per hour |
| 110 km/h | 68.3508 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
How do I convert km/h to mph?
Multiply by 0.621371. 100 km/h is 62.1 mph; 60 mph is 96.6 km/h.
What is a knot?
One nautical mile per hour, 1.852 km/h or 1.151 mph — used at sea and in aviation.
How fast is Mach 1?
About 1,225 km/h (761 mph) at sea level and 15 °C; it falls with altitude as the air gets colder.
What is 1 m/s in km/h?
Exactly 3.6 km/h.
Which countries use mph?
The US and the UK post road speeds in mph; Australia and most of the world use km/h.
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.