A unit of length is a way of measuring length or distance. Length is the long dimension of any object. ... Distance is a numerical description of how far apart things lie. ...

Common units of length in the International System of Units (SI) are: Cover of brochure The International System of Units. ...

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

Non-SI units of length include: The metre, or meter (U.S.), is a measure of length. ... A centimetre (American spelling centimeter, symbol cm) is a unit of length that is equal to one hundredth of a metre, the current SI base unit of length. ... km redirects here. ...

• 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: Femtometre (American spelling: femtometer) is an SI measure of length that is equal to 10−15 (femto) of a metre. ... An angstrom, angström, or Ã¥ngström (symbol Ã…) is a unit of length. ... Picometre (American spelling: picometer) is an SI measure of length that is equal to 10−12 of a metre. ... A micrometre (American spelling: micrometer, symbol µm) is an SI unit of length equal to one millionth of a metre, or about a tenth of the size of a droplet of mist or fog. ... The Imperial units or the Imperial system is a collection of English units, first defined in the Weights and Measures Act of 1824, later refined (until 1959) and reduced. ... U.S. customary units, commonly known in the United States as English units or standard units, are units of measurement that are currently used in the U.S., in some cases alongside units from SI (the International System of Units—the modern metric system). ...

• inch (25.4 mm)
• foot (0.3048 m)
• yard (0.9144 m)
• (terrestrial) mile (1609.344 m)

In addition, the following are used by mariners... An inch (plural: inches; symbol or abbreviation: in or, sometimes, ″ - a double prime) is the name of a unit of length in a number of different systems, including English units, Imperial units, and United States customary units. ... A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′ – a prime) is a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ... A yard (abbreviation: yd) is the name of a unit of length in a number of different systems, including English units, Imperial units, and United States customary units. ... A mile is a unit of length, usually used to measure distance, in a number of different systems, including Imperial units, United States customary units and Swedish/Norwegian mil. ...

• fathom (for depth) (1.8288 m)
• nautical mile (1852 m)

...and surveyors in the United States continue to use... A fathom is the name of a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ... A nautical mile or sea mile is a unit of length. ... Surveyor at work with a leveling instrument. ...

• chain (~20.1m)
• rod (also called pole or perch) (~5 m)

...while horse racing keeps alive: As a unit of measurement within the Imperial system, the chain (surveyors chain, Gunters chain) is defined as 22 yards, 66 feet, or four rods. ... A rod is a unit of length, equal to 5. ... Horse-racing is an equestrian sporting activity which has been practiced over the centuries; the chariot races of Roman times were an early example, as was the contest of the steeds of the god Odin and the giant Hrungnir in Norse mythology. ...

• furlong (~201 m)

Astronomical measure uses: The 5 furlong (1006 m) post on Epsom Downs A furlong is a measure of distance within Imperial units and U.S. customary units. ... A giant Hubble mosaic of the Crab Nebula, a supernova remnant. ...

• astronomical unit (AU) (~149 gigametres)
• light year (ly) (~9.46 petametres)
• parsec (pc) (~30.8 petametres), including kiloparsec (kpc) and megaparsec (Mpc)

Physics also uses: The astronomical unit (AU or au or a. ... A light-year or lightyear, symbol ly, is a unit of length. ... Stellar parallax motion The parsec (symbol pc) is a unit of length used in astronomy. ... Physics (from the Greek, (phúsis), nature and (phusiké), knowledge of nature) is the science concerned with the discovery and understanding of the fundamental laws which govern matter, energy, space, and time. ...

• Planck length
• Bohr radius

Archaic units of distance are described in the article on Ancient weights and measures. They include: The Planck length, denoted by , is the unit of length in the system of units known as Planck units. ... In the Bohr model of the structure of an atom, put forward by Niels Bohr in 1913, electrons orbit a central nucleus. ... This article needs to be cleaned up to conform to a higher standard of quality. ...

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

In everyday conversation, and in informal literature, it is common to see lengths measured in units of objects of which everyone knows the approximate width. Common examples are: A cana was a unit of length used in the former Crown of Aragon. ... Cubit is the name for any one of many units of measure used by various ancient peoples. ... League is a unit of distance long common in Europe and Latin America, although no longer an official unit in any nation. ... The li (里 lǐ) is a Chinese unit of distance, until recently usually considered to be about 576 metres, but is now standardised at a half a kilometre or 500 metres (547 yards). ... A pace (or double-pace) is a measure of distance used in Ancient Rome. ... YOU ARE GAY ... A verst (Russian versta, верста) is an obsolete Russian unit of length. ...

• Football field (generally around 110 metres, depending on the country)
• Widths of a human hair (around 80 micrometres).

Look up Football in Wiktionary, the free dictionary. ... Young Girl Fixing her Hair, by Sophie Gengembre Anderson Hair is a filamentous outgrowth of dead cells from the skin, found only in mammals. ...

See also

• Systems of measurement
• Medieval weights and measures
• English unit