Meter per second (m/s)

The metre per second is the SI unit of speed. Its symbol is m/s. It is a derived unit, formed from the base units of length and time, and it is the speed at which an object covers one metre in one second.

Physics uses nothing else. Every equation of motion, every conservation law and every result in mechanics assumes speeds in metres per second, because mixing in an hour or a mile would force conversion factors into formulas that are otherwise clean. The speed of light in vacuum is exactly 299,792,458 metres per second, a defined value since 1983, and that definition is what fixes the length of the metre.

Outside the laboratory the unit is less comfortable. Road speeds in metres per second would be small numbers with awkward decimals, which is why almost every country signs roads in kilometres per hour instead. Where the metre per second does appear in daily life, it is usually because the quantity is short-lived or physical rather than navigational: wind speed in meteorological reports, the speed of sound at about 343 metres per second in air at twenty degrees Celsius, and lift or conveyor speeds in engineering specifications.

Sport uses it for anything measured over a short course. Sprint velocities, swimming splits and ball speeds are often analysed in metres per second even where the published result is in kilometres per hour, because it makes acceleration and stride analysis straightforward.

A handful of speeds in this unit are worth carrying in memory because so much else is measured against them. Sound travels through dry air at about 343 metres per second at room temperature, through water at 1480 and through steel at some 5000, which is why a distant lightning strike is timed at roughly three seconds to the kilometre. Light in vacuum moves at exactly 299,792,458 metres per second, a number now fixed by definition rather than measured, and the metre itself is derived from it. Between those extremes sit the everyday values: a brisk walk is 1.4 metres per second, a motorway car 33, and a passenger jet about 250.

One metre per second equals 3.6 kilometres per hour, about 2.23694 miles per hour, or about 1.94384 knots.

Meter per second conversion table