Meter (m)

Definition

The SI base unit of length, defined since 1983 by fixing the speed of light at exactly 299 792 458 m/s.

History

The meter was defined in 1793 as one ten-millionth of the distance from the equator to the North Pole, later realised as a platinum bar. Since 1983 it has been defined by fixing the speed of light at exactly 299 792 458 meters per second, tying it to a constant of nature rather than an object.

Where it is used

The meter is the base unit of length across the metric world, used for everything from building plans to sports fields; the United States is the main country that still measures everyday length in feet and inches.

Typical uses include room and building dimensions, sports fields, fabric and rope.

Conversion pages

These pages convert meter to or from another unit in length.

• Foot to meter
• Meter to yard
• Kilometer to meter

Other Length units

• Centimeter (cm)
• Millimeter (mm)
• Kilometer (km)
• Foot (ft)
• Inch (in)
• Yard (yd)
• Mile (mi)

Sources

• BIPM SI BIPM, The International System of Units (SI), 9th ed. (2019) · Dataset reviewed Nov 11, 2026