Speed Converter
Convert km/h, mph, meters per second, knots and Mach — speed limits, wind speeds, running paces and aircraft speeds. Results update as you type; exact factors shown.
One mile per hour is 1.6093 kilometer per hour — see the exact factor, not a rounded rule of thumb.
How the speed converter works
Speeds convert through meters 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 US uses customary units (US gallon, short ton, °F) in daily life; NIST SP 811 gives the exact SI factors.
Common speed conversions
| From | To | Units |
|---|---|---|
| 100 km/h | 62.1371 mph | kilometer per hour to miles per hour |
| 60 mph | 96.5606 km/h | miles per hour to kilometer per hour |
| 1 kn | 1.852 km/h | knot to kilometer per hour |
| 1 m/s | 3.6 km/h | meter per second to kilometer per hour |
| 50 km/h | 31.0686 mph | kilometer per hour to miles per hour |
| 30 mph | 48.2803 km/h | miles per hour to kilometer per hour |
| 1 Ma | 1,225.044 km/h | Mach (sea level, 15 °C) to kilometer per hour |
| 10 m/s | 22.3694 mph | meter per second to miles per hour |
| 70 mph | 112.6541 km/h | miles per hour to kilometer per hour |
| 110 km/h | 68.3508 mph | kilometer per hour to miles per hour |
Units in this converter and their exact factors
| Unit | Symbol | One unit in meter per seconds |
|---|---|---|
| meter per second | m/s | 1 meter per second |
| kilometer per hour | km/h | 0.2777777778 meter per second |
| mile per hour | mph | 0.44704 meter per second |
| knot | kn | 0.5144444444 meter per second |
| foot per second | ft/s | 0.3048 meter per second |
| Mach (sea level, 15 °C) | Ma | 340.29 meter 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 Institute of Standards and Technology (NIST) — United States's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.