Fathom

A fathom is a unit of length in the US customary and imperial systems of measurement that is equal to 6 feet, 2 yards, 72 inches, or 1.828804 meters. It is not part of the International System of Units (SI), nor is it accepted internationally as a non-SI unit. However, historically, the fathom is the most frequently used unit of length for measuring water depth.

A fathom is about the height of a man. The unit originated from the British imperial system and is still used to some degree in the US to measure water depth (meters are also used), such as the depth of water below this boat:

The fathom is not used to measure length outside of nautical contexts. In most other parts of the world, meters (m) are used to measure water depth instead. The list below shows the relationship between fathoms and other commonly used measurements of length.

• 1 fathom = 1.828804 meters
• 1 fathom = 6 feet
• 1 fathom = 60 inches
• 1 fathom = 2 feet

Up until the early 20^th century, the fathom was also used in the United Kingdom to measure the depth of mines. Since most other countries around the world use other units of measurement, it can be helpful to know the conversion factors listed above. Converting to feet (and therefore yards and inches) is relatively simple, though it is worth noting that the US fathom has measurements that slightly differ from the definition used outside the US: 1.828804 m (US) vs. 1.8288 (outside US).