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unit of length in the old imperial and the U.S. customary systems

The fathom is a unit of length. It is used especially when talking about operating ships, to measure the depth of water. It is equal to two yards. The distance between a man's outstreched arms is about a fathom. By this definition, a statute mile is 880 fathoms long. According to the directive 80/181/EWG, one fathom is 1,829 meters long. One fathom is equal to:

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

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.


  1. "Sea measures". Admiralty Manual of Seamanship. HMSO. 1995. p. 1·19. ISBN 0-11-772696-6.