Convert a nonnegative speed between road, marine and scientific units, including mph, km/h, knots, meters per second and feet per second.
Read speed measurements consistently
Select the source unit printed on the measurement, enter the speed and choose a destination. The table also displays the same speed in every supported unit. Reverse a conversion by swapping the source and destination selections; no separate reverse page is needed.
Miles, kilometers, and nautical miles
The international mile is exactly 1.609344 kilometers, so the same factor converts mph to km/h. A knot is one nautical mile per hour, and a nautical mile is exactly 1.852 kilometers. Knots do not mean nautical miles per second.
Speed, velocity, and pace
Speed is the magnitude of motion and is nonnegative. This calculator does not model direction or vector components of velocity. Running pace reverses the relationship to time per distance: at 12 km/h, a kilometer takes 5 minutes. Use the Pace Calculator to work directly with pace and race times.
Mach number depends on the local speed of sound, including the medium and conditions, so a fixed Mach conversion is not included. A constant-speed trip estimate also ignores stops and changing speed.
Formula
km/h = mph × 1.609344
m/s = km/h ÷ 3.6
km/h = knots × 1.852
Examples
A road speed
60 mph is exactly 96.56064 km/h, or 26.8224 m/s.
A marine speed
20 knots is exactly 37.04 km/h, approximately 23.01559 mph.
Precision and definitions
Calculations retain unrounded values internally. Displayed digits do not increase the accuracy of measurements. NIST unit definitions provide the conversion reference.