Speed Converter
Convert between km/h, mph, m/s, knots, and more speed units.
Quick Reference — 1 unit = ? Kilometers per Hour (km/h)
| Unit | Value |
|---|---|
| Meters per Second (m/s) | 3.59999712 |
| Kilometers per Hour (km/h) | 1 |
| Miles per Hour (mph) | 1.609342713 |
| Feet per Second (ft/s) | 1.097279122 |
| Knot (kn) | 1.851996918 |
| Mach (at sea level) | 1225.04302 |
Formula
Multiply by (from factor / to factor)
Everyday Uses
Driving abroad
The sign says 100 km/h and your speedometer thinks in mph (it's 62) — convert limits before the rental car leaves the lot.
Running pace
Treadmill in km/h, race pace in min/mile — convert speeds so your training targets translate to race day.
Wind and weather
Forecast says 40 knots — how bad is that? (74 km/h — very windy.) Convert wind speeds for sailing, flying, or storm prep.
Physics problems
Convert between m/s, km/h, and mph so homework answers land in the units the question demands.
Frequently Asked Questions
How do you convert between km/h and mph?
1 mph = 1.60934 km/h. 1 km/h = 0.62137 mph. To convert mph to km/h, multiply by 1.609 (or ×8÷5). To convert km/h to mph, multiply by 0.621 (or ×5÷8). Common conversions: 30 mph = 48.3 km/h (urban speed limit in UK). 60 mph = 96.6 km/h. 70 mph = 112.7 km/h (UK motorway limit). 100 km/h = 62.1 mph. 120 km/h = 74.6 mph (European motorway). 130 km/h = 80.8 mph.
How fast is the speed of sound (Mach 1), and what is Mach number?
Mach 1 ≈ 340.29 m/s = 1,225 km/h = 761.2 mph at sea level (20°C, dry air). Speed of sound varies with temperature and medium: at 0°C it is 331 m/s; at 35,000 ft altitude (cruising jets), about 295 m/s = 1,062 km/h. Mach number = object speed ÷ local speed of sound. Subsonic: Mach <0.8; Transonic: 0.8–1.2; Supersonic: 1.2–5; Hypersonic: >5. Concorde cruised at Mach 2 (~2,180 km/h); SR-71 Blackbird: Mach 3.3 (~3,540 km/h).
What is a knot and why is it used in aviation and maritime?
1 knot = 1 nautical mile per hour = 1.852 km/h = 1.151 mph. Nautical miles and knots are used in aviation and maritime because 1 nautical mile = 1 arcminute of latitude, making navigation calculations on spherical charts much simpler — distances in nautical miles correspond directly to degrees and minutes on a map. Commercial aircraft cruise at 450–490 knots (830–910 km/h); a typical sailing boat makes 5–10 knots; ocean liners cruise at 20–25 knots.
How do you convert m/s to km/h and mph?
To convert m/s to km/h: multiply by 3.6 (since 1 m/s × 3600 s/hr ÷ 1000 m/km = 3.6). To convert km/h to m/s: divide by 3.6. To convert m/s to mph: multiply by 2.237. Examples: 10 m/s = 36 km/h = 22.4 mph (fast sprint speed); 30 m/s = 108 km/h = 67 mph; 100 m/s = 360 km/h = 224 mph. Wind speeds in weather reports are often given in m/s (meteorology) or mph/km/h (general public). Beaufort scale: 7 m/s = near gale; 17 m/s = storm.
How fast do different things travel in everyday comparison?
Speed reference benchmarks: Walking: 1.4 m/s = 5 km/h = 3.1 mph. Cycling: 5–10 m/s = 18–36 km/h. Sprinting (elite): 12.4 m/s = 44.7 km/h (Usain Bolt record). Car (motorway): 28–36 m/s = 100–130 km/h. Commercial aircraft: 245 m/s = 880 km/h. Speed of sound: 340 m/s = 1,225 km/h. Bullet (rifle): 900–1,200 m/s. Space Shuttle orbital speed: 7,800 m/s = 28,080 km/h. Speed of light: 299,792,458 m/s = 1.08 billion km/h.