### Meters

**Abbreviation/Symbol:**

- m

**Unit of:**

- Length / distance

**Worldwide use:**

The metre, as part of the metric system, is used as a measure of distance across the globe, the primary exception being the United States, where the imperial system is used for most purposes.

**Description:**

The metre is a unit of length in the metric system, and is the base unit of length in the International System of Units (SI).

As the base unit of length in the SI and other m.k.s. systems (based around metres, kilograms and seconds) the metre is used to help derive other units of measurement such as the newton, for force.

**Definition:**

1 m is equivalent to 1.0936 yards, or 39.370 inches.

Since 1983, the metre has been officially defined as the length of the path travelled by light in a vacuum during a time interval of 1/299,792,458 of a second.

**Origin:**

A decimal-based unit of measurement had been proposed as early as the late 17th century, with the name metre being derived from the Greek métron katholikón, meaning 'universal measure'.

An early definition of a metre was "the length of a pendulum with a half-period of one second" By the 18th century a definition based on "one ten-millionth of the length of the Earth's meridian along one quadrant" (the distance from the equator to the North Pole) was gaining favour, and this was the accepted definition when France adopted the metric system in 1795.

Prototype metre bars - first brass, later platinum then a platinum/iridium alloy - were manufactured as successive standards of the metre. In 1960 the metre was redefined using the wavelengths of radiation, before the current definition, relating the metre to the speed of light, was adopted in 1983.

**Common references:**

- A human male of average height is around 1.75 m tall.
- The hurdles used in Olympic 110 m hurdles races are 1.067 m high.
- The tallest building in the world (as of 2012), the Burj Khalifa in Dubai, is 828 m tall.
- The Empire State Building in New York City is 381 m high.
- The standard gauge of railway tracks (the distance between the rails) is 1.435 m.

**Component units:**

- 1/100 m = one centimetre
- 1/1,000 m = one millimetre
- See also micrometre, nanometre, picometre, femtometre, attometre, zeptometre and yoctometre.

**Multiples:**

- The most commonly used multiple is the kilometre (1,000 m), but there are numerous other SI multiples of the metre, including decametre (10 m), hectometre (100 m) and megametre (one million metres).
- The largest SI multiple of the metre is the yottametre, (1,000,000,000,000,000,000,000,000 metres).