🚀 Speed Converter
Convert miles per hour, km/h, knots, meters per second, and feet per second.
Enter a value above to see the result
Common Speed Conversions
| Input | Unit | Result | Unit |
|---|---|---|---|
| 60 | Mile per Hour | 96.56064 | Kilometer per Hour |
| 100 | Kilometer per Hour | 62.137119 | Mile per Hour |
| 1 | Knot | 1.852 | Kilometer per Hour |
| 1 | Meter per Second | 3.6 | Kilometer per Hour |
| 343 | Meter per Second | 1234.8 | Kilometer per Hour |
| 30 | Mile per Hour | 13.4112 | Meter per Second |
About Speed Conversions
Speed measures how quickly an object moves through space — distance covered per unit of time. It comes up everywhere: driving (speed limits), sports (a fastball's pitch speed, a runner's pace per mile), aviation (aircraft cruising speed), and science (the velocity of particles or waves).
In the United States and the United Kingdom, road speeds are measured in miles per hour (mph). Most other countries use kilometers per hour (km/h). In aviation and maritime navigation, the knot is the universal standard — one knot equals exactly one nautical mile per hour (1.852 km/h). Air traffic controllers and ship captains worldwide use knots regardless of their home country.
In physics, the SI unit for speed is the meter per second (m/s). Important reference speeds: sound travels at approximately 343 m/s (1,235 km/h or 767 mph) in air at sea level. The speed of light in a vacuum is exactly 299,792,458 m/s — the fastest possible speed in the universe and a cornerstone of modern physics.
Frequently Asked Questions
How fast is 100 km/h in miles per hour?
100 km/h equals approximately 62.14 mph. A useful rule of thumb: multiply km/h by 0.621 to estimate mph, or divide mph by 0.621 to estimate km/h. This conversion is especially common when driving in countries using a different speed system.
What is a knot and how does it compare to mph?
A knot is one nautical mile per hour, equal to approximately 1.151 mph or 1.852 km/h. It is the standard speed unit in aviation and maritime navigation worldwide. A ship traveling at 20 knots is moving at about 23 mph.
What is the speed of sound?
The speed of sound in dry air at sea level is approximately 343 m/s, or about 1,235 km/h (767 mph). This is called Mach 1. Speed of sound varies with temperature and medium — it travels faster in warmer air and much faster through solids like steel.
How fast is the speed of light?
The speed of light in a vacuum is exactly 299,792,458 m/s — approximately 1,080,000,000 km/h or 671,000,000 mph. This is a universal physical constant (denoted c) and the ultimate speed limit in the universe.
What is the difference between speed and velocity?
Speed is a scalar quantity — it tells you how fast something is moving (e.g., 60 mph). Velocity is a vector — it includes both speed and direction (e.g., 60 mph heading north). In everyday conversation the two terms are used interchangeably, but they are distinct in physics.
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All conversion results are provided for general informational purposes only. Our formulas use internationally recognized conversion factors; however, rounding may affect precision. Do not rely on these results for professional, medical, legal, or engineering decisions without independent verification. Read our full disclaimer.