Speed Converter

Convert between mph, km/h, m/s, knots, and feet per second instantly.

Whatever unit you pick, your figure is first pushed into metres per second, then pulled back out into all five columns at once and rounded to four decimal places. The factors are worth knowing. A mile per hour is exactly 0.44704 m/s, which follows from the 1959 agreement fixing the international mile at 1609.344 metres. A foot per second is exactly 0.3048 m/s. The knot is the odd one: it is one international nautical mile of 1852 metres per hour, or 0.5144444... m/s repeating, and this engine stores it truncated as 0.514444, so a knot reading drifts by roughly one part in a million — invisible at chart-plotting scale, but it is a truncation and not an exact factor. Two things are outside its scope. There is no Mach column, because the speed of sound is not a constant and depends on air temperature, so no single factor could be honest. And speed here is a scalar magnitude, with the input floored at zero: no heading, no wind vector, and therefore no way to separate airspeed from ground speed.