Conversion from Miles per hour to Meters per second

Information about the Mile per hour (mph)

The mile per hour is a unit of speed equal to one mile travelled in one hour. Its symbol is mph. It is the road speed unit of the United States and the United Kingdom, and of a small number of territories connected to them, and it is used almost nowhere else.

Britain's position is the odd one. The country converted its shops, its schools and its industry to metric units over the second half of the twentieth century, but left road signs alone. Distances appear in miles and yards, speed limits in miles per hour, and a plan to change them has been announced and abandoned more than once, largely because replacing every sign in the country is expensive and the political return is small.

The number sixty is what makes the unit intuitive to those who grew up with it. At sixty miles per hour a vehicle covers a mile a minute, which turns journey planning into simple mental arithmetic. Speed limits cluster around convenient multiples: thirty in towns, seventy on British motorways, sixty-five or seventy on most American interstates.

Sport and weather keep it alive beyond the road. Baseball pitch speeds, tennis serves and cricket deliveries are quoted in miles per hour in English-language coverage worldwide, and hurricane wind speeds in the Atlantic basin are reported the same way, with the Saffir-Simpson categories defined by thresholds in miles per hour.

Records set in the unit have become cultural landmarks in their own right. The four-minute mile is a pace of fifteen miles per hour, the sound barrier at sea level lies near 767, and the land speed record has stood above 700 since 1997. Everyday driving figures carry the same weight of familiarity: 30 miles per hour in a built-up area, 70 on a motorway, and the observation that a car doing 60 covers 88 feet in a second, which is the number American driving instructors use to explain following distances. Because the unit rarely appears in physics, almost all of its landmarks come from the road, the track and the runway.

One mile per hour equals about 1.609344 kilometres per hour, about 0.44704 metres per second, or about 0.868976 knots.

Information about the 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.