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m/s, km/h, mph, knots.
The speed converter changes a rate of motion between metres per second (m/s), kilometres per hour (km/h), miles per hour (mph), knots and feet per second, updating live as you type.
Each unit is defined by its value in metres per second, the SI base for speed, so every conversion is exact in both directions.
Definitions: 1 km/h = 1/3.6 m/s, 1 mph = 0.44704 m/s, 1 knot = 0.514444 m/s, 1 ft/s = 0.3048 m/s.
A knot is one nautical mile per hour, and a nautical mile (1852 m) is longer than a statute mile (1609.344 m), so 1 knot ≈ 1.15 mph.
Divide by 3.6. For example 90 km/h ÷ 3.6 = 25 m/s.
The SI unit is metres per second (m/s), which is why this tool uses it as the base for every conversion.