A fathom is a unit of length in the imperial and the U.S. customary systems equal to 6 feet (1.8288 metres), used especially for measuring the depth of water. There are two yards (6 feet) in a fathom.
Equivalent to A Fathom
One fathom is equal to:
- 2 yards (1 yard is exactly 1/2 of a fathom)
- 6 feet (1 foot is exactly 1/6 of a fathom)
- 72 inches
- 1.8288 meters
The length of the six rulers combined is equivalent to a fathom.
A fathom was originally based off of the distance between a man's outstretched arms.
Fathom Used in Measuring Depth of Water
To measure the depth of shallow waters, boatmen used a sounding line containing fathom points, some marked and others in between, called deeps, unmarked but estimated by the user. Water near the coast and not too deep to be fathomed by a hand sounding line was referred to as in soundings or on soundings. The area offshore beyond the 100 fathom line, too deep to be fathomed by a hand sounding line, was referred to as out of soundings or off soundings. A deep-sea lead, the heaviest of sounding leads, was used in water exceeding 100 fathoms in depth.