Speed Converter
km/h · mph · m/s · Knots · Mach
Enter a speed and select units to convert.
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Speed Quick Reference
Common speed conversions and real-world reference points.
| Reference | km/h | mph | m/s |
|---|---|---|---|
| Walking pace | 5 | 3.1 | 1.39 |
| City speed limit | 50 | 31.1 | 13.9 |
| Motorway limit (UK) | 112 | 70 | 31.1 |
| Motorway limit (DE) | 130 | 80.8 | 36.1 |
| Cruising airliner | 900 | 559 | 250 |
| Speed of sound (sea level) | 1,235 | 767 | 343 |
Mach 1 at sea level = 1,235 km/h (767 mph) at 15°C. Speed of sound varies with temperature and altitude. 1 knot = 1 nautical mile per hour = 1.852 km/h.
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Speed Conversion Questions
How do I convert km/h to mph?+
Multiply km/h by 0.621371 to get mph. Example: 100 km/h = 62.14 mph. To go the other way, multiply mph by 1.60934. Quick mental trick: multiply by 5 and divide by 8 (e.g. 80 km/h × 5 ÷ 8 = 50 mph). Common conversions: 50 km/h = 31.1 mph · 100 km/h = 62.1 mph · 120 km/h = 74.6 mph.
What is a knot in km/h and mph?+
One knot = 1.852 km/h = 1.151 mph = 0.5144 m/s. A knot is one nautical mile per hour. It is used in aviation and maritime navigation because nautical miles correspond to degrees of latitude. A ship travelling at 20 knots is moving at 37 km/h (23 mph). Cruising speed for a large container ship is about 20–25 knots.
What is Mach 1 in km/h and mph?+
Mach 1 at sea level and 15°C = 1,235 km/h (767 mph, 343 m/s). The speed of sound varies with temperature and altitude: at cruising altitude (−57°C), it is about 1,062 km/h (660 mph). A commercial jet cruises at roughly Mach 0.85 (900 km/h). The Concorde cruised at Mach 2.04 (2,179 km/h).
How do I convert m/s to km/h?+
Multiply m/s by 3.6 to get km/h. Example: 10 m/s = 36 km/h. To convert km/h to m/s, divide by 3.6. This is because 1 km/h = 1000 m / 3600 s = 1/3.6 m/s. Physics problems typically use m/s; road signs use km/h or mph; weather wind speeds often use m/s or knots.
How fast is the speed of light?+
The speed of light in a vacuum is exactly 299,792,458 m/s = 1,079,252,849 km/h = 670,616,629 mph. It is defined as a physical constant and is used to define the meter. Nothing with mass can reach the speed of light. Light takes about 8 minutes 20 seconds to travel from the Sun to the Earth.
What is the speed limit in mph and km/h for common countries?+
Common motorway speed limits: UK: 70 mph (112 km/h) · USA: typically 65–80 mph (105–129 km/h) · Germany (Autobahn): advisory 130 km/h (81 mph), no general limit on unrestricted sections · France: 130 km/h (81 mph) · Australia: 110 km/h (68 mph). Urban limits are typically 50 km/h (31 mph) or 30 mph (48 km/h).
How fast do commercial airplanes fly in mph and km/h?+
Commercial jets cruise at approximately 850–950 km/h (530–590 mph), typically around Mach 0.82–0.85. This is the ground speed in still air; actual ground speed varies with wind (jet streams can add 150 km/h tailwind). Take-off speed is about 260–290 km/h (160–180 mph) and landing speed about 240–260 km/h (150–160 mph).
How fast can humans run in km/h and mph?+
Usain Bolt's world record 100m sprint peak speed: 44.72 km/h (27.8 mph). Average recreational runner: 8–12 km/h (5–7.5 mph). Marathon world record pace: ~20.5 km/h (12.7 mph). Walking pace: 4–6 km/h (2.5–3.7 mph). The average person cannot sustain more than 15–20 km/h for more than a few seconds.
What is feet per second (fps) used for?+
Feet per second (ft/s or fps) is used in US ballistics, firearms, and some engineering contexts. 1 ft/s = 0.3048 m/s = 1.09728 km/h = 0.6818 mph. Bullet velocities are typically 300–1,000 m/s (980–3,280 fps). The muzzle velocity of a typical 9mm handgun is about 370 m/s (1,214 fps). fps is also used in athletics for sprint analysis.
How fast is the wind in different speed scales?+
The Beaufort scale classifies wind by effect: Force 0 (calm, 0 km/h) to Force 12 (hurricane, 118+ km/h). A gentle breeze (Force 3) = 12–19 km/h (7–12 mph). Gale (Force 8) = 62–74 km/h (39–46 mph). Hurricane (Force 12) = 118+ km/h (73+ mph). The Saffir-Simpson scale classifies hurricanes: Category 1 starts at 119 km/h (74 mph), Category 5 exceeds 252 km/h (157 mph).