Unit of length

A unit of length is a way of measuring length or distance.

Common units of length in the International System of Units (SI) are:

• metre (or "meter") and its multiples, such as "centimetre" or "kilometre"

Non-SI units of length include:

• fermi (fm) (= 1 femtometre in SI units)
• angstrom (Å) (= 100 picometres in SI units)
• micron (= 1 micrometre in SI units)

Common Imperial units and U.S. customary units of length include:

• inch
• foot
• yard
• (terrestrial) mile

In addition, the following are used by mariners...

• fathom (for depth)
• nautical mile

...and surveyors in the United States continue to use...

• chain
• rod

...while horse racing keeps alive:

• furlong

Astronomical measure uses:

• astronomical unit (AU)
• light year (ly)
• parsec (pc), including kiloparsec (kpc) and megaparsec (Mpc)

Physics also uses:

• Planck length
• Bohr radius

Archaic units of distance are described in the article on Historical weights and measures. They include:

• cana
• cubit
• league
• li (China)
• pace (the "double pace" of about 5 feet used in Ancient Rome)
• verst (Russia)