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Fathom to Meter Converter

Enter a depth in fathoms to convert to metres and feet.

How it is calculated

Two fixed factors are applied to the number of fathoms you enter: metres = fathoms × 1.8288 and feet = fathoms × 6. One fathom is defined as exactly 6 feet, and one foot is 0.3048 m, which gives 1.8288 m. Both results are rounded to two decimals for display and shown with their unit (m and ft). Decimal fathoms are accepted, and a negative number simply gives a negative result, because the tool does not check the sign. To go the other way, divide metres by 1.8288. The conversion is the same for water depth, rope length or any other length measured in fathoms.

Worked example

A sounding on a chart reads 12.5 fathoms. In feet that is 12.5 × 6 = 75.00 ft. In metres it is 12.5 × 1.8288 = 22.86 m. You can check it from the feet: 75 × 0.3048 = 22.86 m, the same answer. A vessel drawing 4 m can therefore pass over this spot with about 18.86 m of water to spare, ignoring tide and the chart datum.

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Common mistakes

  • Rounding 1 fathom to 2 m: that makes 12.5 fathoms look like 25 m instead of 22.86 m, an error of almost 10%.
  • Treating the number as feet or metres already: the field is in fathoms, and a chart depth of 12 means 12 fathoms (72 ft), not 12 ft.
  • Reading a depth written as fathoms plus feet as a decimal: for example 12 fathoms 3 ft is 12 + 3 ÷ 6 = 12.5 fathoms, not 12.3.
  • Forgetting that depths on a chart are relative to a reference level: the converted figure is the charted depth, not the actual water depth at the current tide.

About this calculator

This converter turns a depth in fathoms into metres and feet using the modern standardized value 1 fathom = 6 feet = 1.8288 m. The fathom traditionally comes from the span of a sailor's outstretched arms, roughly the distance needed to haul in a length of rope hand over hand.

Sailors, hydrographers and scuba divers still use fathoms on nautical charts and depth soundings, particularly in the US, UK and other countries with a strong maritime tradition, even though most scientific and engineering work has moved to metres — making a quick fathom-to-metre conversion a routine task when cross-referencing older charts against modern GPS and sonar data.

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  • Editorial team

    Some older charts give a depth as fathoms plus feet rather than as a decimal. Convert the feet to a fraction of a fathom first: 3 fathoms 2 feet is 3 plus 2 over 6, so enter 3.3333 and the tool returns 20.00 ft and about 6.10 m. The result is a plain length, so it carries no allowance for tide or for the chart datum, which you still need to read from the chart itself. Which charts or soundings are you comparing?

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