Speed Converter
Convert between metres per second, km/h, mph, knots, Mach number, feet per second, speed of light, and more — all speed and velocity units instantly.
All Unit ConvertersAll conversions from 100 km/h
| Unit | Symbol | Value |
|---|
Speed and Velocity Units Explained
Speed is the magnitude of velocity — distance covered per unit of time. The SI unit is metres per second (m/s). Road speeds use km/h in most of the world and mph in the US, UK, and a few other countries.
The Mach number is not a fixed speed — it is the ratio of an object’s speed to the local speed of sound, which varies with altitude and temperature. Mach 1 at sea level (20°C) is approximately 343 m/s. At 11 km altitude it drops to about 295 m/s.
Road
km/h (most countries) and mph (US, UK). 100 km/h ≈ 62.14 mph. Speed limit signs differ by country.
Aviation / Maritime
Knots (nautical miles per hour). 1 knot = 1.852 km/h = 1.15078 mph. Used universally in air and sea navigation.
Scientific
m/s is the SI base unit. c (speed of light) = 299,792,458 m/s — the cosmic speed limit.
Aeronautics
Mach number. Below Mach 1 = subsonic; Mach 1 = sonic; above Mach 1 = supersonic; above Mach 5 = hypersonic.
Common Questions
FAQ: Speed Converter
Multiply km/h by 0.621371 to convert to mph. To convert mph back to km/h, multiply by 1.60934. For example, 100 km/h equals approximately 62.14 mph.
At sea level and around 20°C, Mach 1 is approximately 343 m/s, 1,235 km/h or 767 mph. Since the speed of sound changes with temperature and altitude, Mach values vary with atmospheric conditions.
One knot equals exactly 1.852 km/h or approximately 1.15078 mph. Knots are widely used in aviation and maritime navigation because they are based on nautical miles.
Multiply miles per hour (mph) by 1.60934 to obtain kilometres per hour (km/h). For example, 60 mph equals approximately 96.56 km/h.
MPH measures speed using miles per hour and is primarily used in the United States and the United Kingdom. KM/H uses kilometres per hour and is the standard speed unit in most other countries.
A knot is a unit of speed equal to one nautical mile per hour. It is commonly used by ships, aircraft and meteorologists because nautical miles are based on the Earth’s geometry.
The speed of sound depends mainly on air temperature. Warmer air allows sound waves to travel faster, while colder air reduces the speed of sound. This is why Mach numbers vary with altitude.
The converter supports kilometres per hour (km/h), miles per hour (mph), metres per second (m/s), feet per second (ft/s), knots, Mach and other commonly used speed units.
Speed conversions are commonly used for road travel, aviation, shipping, motorsports, weather forecasting, engineering and scientific calculations.
Yes. The converter uses internationally accepted conversion factors for all supported speed units, including km/h, mph, knots, metres per second, feet per second and Mach.