🏎️ Speed Converter
Convert between km/h, mph, m/s, ft/s, knots, and Mach number. Results update as you type.
Quick Reference
Understanding Speed Units
Speed measures how fast something moves — the distance traveled per unit of time. Different speed units are used in different contexts.
Common Conversion Factors
| From | To | Multiply by |
|---|---|---|
| km/h | mph | 0.621371 |
| mph | km/h | 1.60934 |
| m/s | km/h | 3.6 |
| knots | km/h | 1.852 |
| Mach 1 | km/h | 1,234.8 (at sea level) |
Speed Unit Use Cases
- km/h — Road speeds in most countries, weather reports (metric countries)
- mph — Road speeds in the US, UK, and a few other countries
- m/s — Scientific measurements, physics calculations, wind speed (SI unit)
- Knots — Maritime and aviation speed. 1 knot = 1 nautical mile per hour
- Mach — Aircraft speed relative to the speed of sound. Mach 1 ≈ 1,234.8 km/h at sea level
Notable Speeds
| What | km/h | mph |
|---|---|---|
| Walking | 5 | 3.1 |
| Cycling | 15–25 | 9–16 |
| City driving | 50 | 31 |
| Highway driving | 100–120 | 62–75 |
| Speed of sound | 1,234.8 | 767.3 |
| Speed of light | 1,079,252,849 | 670,616,629 |
Frequently Asked Questions
Multiply km/h by 0.621371 to get mph. For a quick estimate, multiply by 0.6. Example: 100 km/h ≈ 62 mph.
A knot is 1 nautical mile per hour (1.852 km/h or 1.151 mph). It's used in aviation and maritime navigation because nautical miles relate directly to latitude and longitude coordinates.
Mach number is the ratio of speed to the speed of sound. Mach 1 = speed of sound (about 1,234.8 km/h at sea level, 15°C). Supersonic aircraft fly above Mach 1. The Concorde cruised at Mach 2.04.