Fathom

A fathom is a unit of length in the US customary and imperial systems of measurement equal to 6 feet or 1.8288 meters.

What is a fathom

A fathom is a measurement of length that is specifically used to measure the depth of water in the US customary and imperial systems of measurement. Because the fathom is neither an SI (International System of Units) unit nor one that is accepted for use within SI, it is a rarely used unit of measurement. It is only used in nautical contexts in the United States due to tradition. Most other countries around the world use meters to measure water depth instead.

Fathom definition

The fathom today is defined as 6 feet or 1.8288 meters. Its original definition however, was based on the distance between the tip of the middle finger of one hand to that of the other hand when both arms are fully stretched out. Since only sailors typically used fathoms to measure water depth, the definition of the fathom was generally based on the arm span of the average sailor of the time, which was approximately 6 feet.

Also, the fathom used to be defined based on the US survey foot rather than the international foot, though this definition is only slightly different. Based on the US survey foot, the fathom is equal to 1.828804 meters rather than 1.8288 meters using the international foot.

Fathom meaning

The term "fathom" was derived from the Old English term "fæðm" which means "a pair of outstretched arms." The definition of a fathom equalling approximately 6 feet was based on the average arm span of sailors of the time, since only sailors or those with maritime occupations had a need to measure water depth.

How deep is a fathom

A fathom is 6 feet or 1.8288 meters deep. Below are other common measures of length and their relationship to a fathom.

• 1 fathom = 1.8288 meters (based on international feet)
• 1 fathom = 1.828804 meters (based on US survey feet)
• 1 fathom = 6 feet
• 1 fathom = 60 inches
• 1 fathom = 2 yards

Fathom usage

Historically, the fathom was the most widely used measure of water depth. It was also used to measure the depth of mines in the UK up until the 20th century and for burials at sea, which required a minimum depth of 6 fathoms.

Since the widespread adoption of SI, the fathom has been replaced by the meter for measurements of water depth in most countries (with the exception of countries such as the US).

How to convert fathoms

Since most other countries around the world use other units of measurement, it can be helpful to know how to convert fathoms to other units of length. To convert between fathoms and other measurements, we need to know the appropriate conversion factors.

Fathoms to feet

To convert fathoms to feet, multiply a value in fathoms by 6.

Fathoms to meters

To convert fathoms to meters, multiply a value in fathoms by 1.8288.

Fathoms to yards

To convert fathoms to yards, multiply a value in fathoms by 2.

Fathoms to inches

To convert fathoms to inches, multiply a value in fathoms by 72. Below are some fathom conversion examples.

Fathom conversion table

The table below converts fathoms to common measures of feet and meters.