Speed Calculator & Velocity Converter
From the highway to the runway. Instantly convert between Miles per Hour, Kilometers per Hour, Knots, Meters per Second, and even Mach number.
Convert Speed
Quick Conversions
Results
Enter speed value and select units to convert
Speed Visualization
Common Speeds
Speed Conversion Factors
mph to kph
1 mph = 1.60934 kph
kph to m/s
1 kph = 0.277778 m/s
knots to mph
1 knot = 1.15078 mph
mach to m/s
1 mach = 343 m/s (at sea level)
Speed vs. Velocity: What's the Difference?
While often used interchangeably in daily conversation, Speed and Velocity have distinct meanings in physics.
Speed (Scalar)
Speed is simply "how fast" something is moving. It has magnitude
but no direction.
Example: "The car is traveling at 60 mph."
Velocity (Vector)
Velocity is speed plus direction. It is a
vector quantity.
Example: "The car is traveling at 60 mph North."
Why Do We Use Different Units?
Knots (Maritime/Air)
Sailors and pilots use Knots because 1 knot equals 1 Nautical Mile per hour. Since 1 Nautical Mile is exactly 1 minute of latitude on Earth, it makes chart navigation incredibly simple.
KPH (Global Standard)
Kilometers per Hour is the standard for 95% of the world's roads. It fits seamlessly with the metric system (1000m = 1km), making mental math easier for distance estimates.
Mach (Supersonic)
Named after Ernst Mach, this unit represents the ratio of speed relative to the speed of sound. Mach 1 is the sound barrier. It varies with altitude and temperature but is vital for jet aircraft.
The Mach Scale
| Regime | Mach Number | Example |
|---|---|---|
| Subsonic | < 0.8 | Commercial Airliners (Mach 0.85) |
| Transonic | 0.8 - 1.2 | Breaking the Sound Barrier |
| Supersonic | 1.2 - 5.0 | F-22 Raptor, Concorde |
| Hypersonic | 5.0 - 10.0 | X-15 Rocket Plane |
Common Questions
Why is 1 knot not equal to 1 mph?
A "statute mile" (MPH basis) is 5,280 feet. A "nautical mile" (Knot basis) is based on the Earth's circumference and is approximately 6,076 feet. Therefore, 1 Knot is about 1.15 MPH.
How fast is Usain Bolt?
During his world record 100m sprint (9.58s), Usain Bolt reached a top speed of 27.8 mph (44.72 kph).
Does Mach 1 change speed?
Yes. The speed of sound depends on air temperature. At sea level (20°C), Mach 1 is ~767 mph. At 35,000 ft where it's colder (-50°C), Mach 1 is only ~660 mph.