🔄 Unit Converters
Speed Converter
Convert between miles per hour, km/h, meters per second, knots, Mach and feet per second instantly.
Enter any speed — all units update live.
Quick Reference
1 mph = 1.60934 km/h
1 knot = 1.852 km/h
1 m/s = 3.6 km/h
Mach 1 ≈ 1235 km/h
Speed of light ≈ 299,792 km/s
1 ft/s = 0.3048 m/s
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Free Online Speed Converter
Our free speed converter converts between all common units of speed — kilometres per hour (km/h), miles per hour (mph), metres per second (m/s), feet per second (ft/s) and knots. It's useful for driving, aviation, sailing, physics calculations, sports performance tracking and international travel.
All speed units update simultaneously as you type — enter a value in any field and instantly see the equivalent in all other units. No conversion button needed.
🚗 km/h & mph
Essential for international driving and understanding speed limits.
✈️ Knots
Aviation and maritime speed — used by pilots and sailors worldwide.
🔬 m/s & ft/s
Scientific and engineering speed units for physics calculations.
⚡ Instant
All units update simultaneously — no button needed.
Common Speed Conversions
- 100 km/h = 62.14 mph (typical motorway speed)
- 60 mph = 96.56 km/h (UK motorway speed limit)
- 1 knot = 1.852 km/h = 1.15078 mph
- Speed of sound = 343 m/s = 1,235 km/h = 767 mph
- Speed of light = 299,792,458 m/s ≈ 1.08 billion km/h
- 30 mph = 48.28 km/h (typical urban speed limit)
- Usain Bolt top speed ≈ 44.72 km/h = 27.79 mph
Frequently Asked Questions
How do I convert km/h to mph?
Multiply the km/h value by 0.621371 to get mph. As a quick approximation, multiply by 0.6 or divide by 1.6. For example, 100 km/h × 0.621371 ≈ 62.1 mph. Going the other way, multiply mph by 1.60934 to get km/h.
What is a knot?
A knot is a unit of speed equal to one nautical mile per hour. One nautical mile is 1,852 metres (slightly longer than a standard kilometre). Knots are used in aviation and maritime navigation worldwide. A ship travelling at 20 knots is going 37.04 km/h or 23.02 mph.
What speed is Mach 1?
Mach 1 is the speed of sound, which varies depending on altitude and temperature. At sea level at 20°C, the speed of sound is approximately 343 m/s, 1,235 km/h or 767 mph. Aircraft that travel faster than this are called supersonic. The Concorde cruised at about Mach 2 (2,470 km/h).
Why do different countries use different speed units?
Most countries use kilometres per hour (km/h) as part of the metric system. The United States, United Kingdom and a few other countries still use miles per hour (mph) due to historical conventions. This makes speed converters particularly useful when driving abroad or reading international news about vehicle speeds.