A speed converter changes a rate of travel from one unit into another — kilometres per hour to miles per hour, or metres per second to knots. You need it when reading road signs abroad, comparing vehicle specifications, following weather reports, or working with physics problems where SI units are required. This tool covers km/h, mph, m/s, ft/s and the knot.
The formula. Every value passes through one base unit, the metre per second. The exact factors are 1 km/h = 1 ÷ 3.6 m/s, 1 mph = 0.44704 m/s, 1 ft/s = 0.3048 m/s and 1 knot = 0.514444 m/s (one nautical mile per hour). A value is multiplied to metres per second, then divided by the target unit's factor: result = value × factor(from) ÷ factor(to).
Worked example. A 100 km/h motorway limit is 100 ÷ 3.6 = 27.78 m/s, and dividing by 0.44704 gives 62.14 mph. A useful shortcut: divide km/h by 1.609 to get mph, so 80 km/h ≈ 50 mph and 120 km/h ≈ 75 mph. In the other direction, a 30 mph urban limit is about 48 km/h.
Where it's used. Speed conversion matters for drivers crossing borders, since most of the world posts km/h while the US and UK post mph. Aviation and shipping use knots because a nautical mile is tied to one minute of latitude, making navigation arithmetic simple. Physics and engineering work in m/s, wind speeds appear in km/h, mph or knots depending on the forecaster, and running pace converts between min/km and min/mile the same way.