- published: 25 Oct 2013
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A fathom (abbreviation: ftm) = 1.8288 meters, is a unit of length in the imperial and the U.S. customary systems, used especially for measuring the depth of water.
There are two yards (6 feet) in an imperial or U.S. fathom. Originally based on the distance between the man's outstretched arms, the size of a fathom has varied slightly depending on whether it was defined as a thousandth of an (Admiralty) nautical mile or as a multiple of the imperial yard. Formerly, the term was used for any of several units of length varying around 5–5+1⁄2 feet (1.5–1.7 m).
The name derives from the Old English word fæðm meaning embracing arms or a pair of outstretched arms. In Middle English it was fathme. A cable length, based on the length of a ship's cable, has been variously reckoned as equal to 100 or 120 fathoms. At one time, a quarter meant a fourth of a fathom.
Abbreviations: f, fath, fm, fth, fthm.
One fathom is equal to:
In 1959 the United States, Australia, Canada, New Zealand, South Africa, and the United Kingdom defined the length of the international yard to be exactly 0.9144 metre. With the adoption of the metric SI system the use of fathoms declined.