# Unit of length: Wikis

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# Encyclopedia

## Contents

Many different units of length have been used across the world. The main units in modern use are U.S. customary units in the United States and the Metric system elsewhere. British Imperial units are still used for some purposes in the United Kingdom and some other countries. The metric system is sub-divided into SI and non-SI units.

## Metric system

### SI units

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

### Non-SI units

Non-SI units of length include:

## Imperial/US units

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

• inch (25.4 mm)
• mil (one thousandth of an inch, one thou)
• foot (12 inches, 0.3048 m)
• yard (3 ft, 0.9144 m)
• (terrestrial) mile (5280 ft, 1609.344 m)

## Marine

In addition, the following are used by mariners:

## Surveying

Surveyors in the United States continue to use:

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

## Astronomical

Astronomical measure uses:

## Archaic units

Archaic units of distance include:

## Informal units

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:

• Double-decker bus (9.5–10.9 metres in length)
• Football field (generally around 110 metres, depending on the country)
• Widths of a human hair (around 80 micrometres)
• A beard-second is a unit created as a teaching concept. It is the distance that a beard grows in a second (about 5 nanometres)
• Smoot, a jocular unit of length created as part of an MIT fraternity prank

## Other

Horse racing keeps alive:

Physics also uses:

# Simple English

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

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

But there are a lot of units that do not fit in the SI-System:

• fermi (fm) (= 1 femtometre in SI units)
• angstrom (Å) (= 100 picometres in SI units)
• micron (= 1 micrometre in SI units)
• Norwegian/Swedish mil (= 10,000 metres)

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

• inch (25.4 mm)
• mil (one thousandth of an inch, one thou)
• foot (0.3048 m, 12 inches)
• yard (0.9144 m)
• (terrestrial) mile (1609.344 m)

In addition, the following are used by mariners:

Surveyors in the United States continue to use:

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

Horse racing keeps alive:

Astronomical measure uses:

Physics also uses:

Old units of distance are:

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:

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