MPH to KM/H Converter
Convert miles per hour to kilometers per hour — multiply by 1.609. 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 mph to km/h 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 |
|---|---|---|
| 10 mph | 16.0934 km/h | miles per hour to kilometer per hour |
| 20 mph | 32.1869 km/h | miles per hour to kilometer per hour |
| 30 mph | 48.2803 km/h | miles per hour to kilometer per hour |
| 40 mph | 64.3738 km/h | miles per hour to kilometer per hour |
| 50 mph | 80.4672 km/h | miles per hour to kilometer per hour |
| 55 mph | 88.5139 km/h | miles per hour to kilometer per hour |
| 60 mph | 96.5606 km/h | miles per hour to kilometer per hour |
| 65 mph | 104.6074 km/h | miles per hour to kilometer per hour |
| 70 mph | 112.6541 km/h | miles per hour to kilometer per hour |
| 75 mph | 120.7008 km/h | miles per hour to kilometer per hour |
| 80 mph | 128.7475 km/h | miles per hour to kilometer per hour |
| 100 mph | 160.9344 km/h | miles per hour to kilometer 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
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 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.