Fathom

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This article is about Fathom (unit of length). For other uses, see Fathom (disambiguation).

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. The name derives from the Old English word fæthm (plural) meaning 'outstretched arms' which was the original definition of the unit's measure.^[1] In Middle English it was fathme. Its size can vary from system to system. The most commonly used fathom today is the international fathom. There are 2 yards or 6 feet in a fathom.

[edit] International fathom

In 1958 the United States and countries of the Commonwealth of Nations defined the length of the international yard to be 0.9144 metres. Consequently, the international fathom is defined to be equal to 1.8288 metres.

[edit] Equivalence to other units of length

1 international fathom is equal to:

• 6 feet (1 foot is about 0.1667 fathoms)
• 2 yards (1 yard is 0.5 fathoms)
• 1.8288 metres (1 metre is about 0.5468 fathoms)
• 72 inches

[edit] Use of the fathom

Once also used for measuring distances on land, the fathom is now restricted to nautical uses, especially expressing the depth of water or the length of nautical rope or cable. Until early in the twentieth century, it was the unit used to measure the depth of mines in Cornwall, England. The verb "to fathom" means to measure the depth of something, especially using a sounding line.

Civilian maps in English-speaking countries used to have depths commonly marked in fathoms, but this has changed to metres generally, even in US maps. Nautical charts have changed on a separate schedule.

[edit] Other fathoms and similar units of length

Units of length similar to the size of the fathom can be found in many cultures. Some are listed below.

[edit] See also

• English unit
• Imperial unit
• United States customary units
• International System of Units
• Ancient Greek units of measurement