Speed Units Guide
Convert mph, km/h, knots, and m/s — with international speed limit comparisons
Overview
Speed is measured as distance traveled per unit of time. The most common units are miles per hour (mph) in the US/UK, kilometers per hour (km/h) in most other countries, and knots for maritime and aviation use.
Understanding speed units is essential for driving internationally, understanding weather reports, and aviation.
Common Speed Units
mph
Miles per hour
US, UK roads
1 mph = 1.609 km/h
km/h
Kilometers per hour
Most countries
1 km/h = 0.621 mph
m/s
Meters per second
Scientific use
1 m/s = 3.6 km/h
knot
Nautical mile/hour
Ships, planes
1 knot = 1.852 km/h
International Speed Limit Comparison
| Road Type | USA (mph) | UK (mph) | Europe (km/h) | Australia (km/h) |
|---|---|---|---|---|
| Residential | 25-30 | 20-30 | 30-50 | 50 |
| Urban | 35-45 | 30-40 | 50 | 60 |
| Rural | 55-65 | 60 | 80-100 | 100 |
| Highway | 65-85 | 70 | 110-130 | 110 |
Remember: 100 km/h ≈ 62 mph, and 60 mph ≈ 97 km/h. A useful approximation!
Conversion Formulas
mph to km/h
km/h = mph x 1.60934km/h to mph
mph = km/h x 0.62137Knots to km/h
km/h = knots x 1.852Reference Speeds
5 km/h Walking pace
15 km/h Cycling (casual)
45 km/h Sprinting (Usain Bolt)
120 km/h Highway driving
300 km/h High-speed train
900 km/h Commercial airplane
1,235 km/h Speed of sound
28,000 km/h ISS orbital speed