Fathom to Foot Converter

How it is calculated

The conversion uses the fixed ratio 1 fathom = 6 ft. Fathoms to feet: ft = fathoms × 6. Feet to fathoms: fathoms = ft ÷ 6. The direction field selects which way to go; anything other than the feet-to-fathoms option is treated as fathoms to feet. Results are rounded to two decimals, so 1 ft shows as 0.17 fathom although the calculation itself is exact (the rate line gives 0.16667). The tool also shows a check line converting the answer back to the starting unit. Negative values are converted with their sign (-3 fathoms is -18.00 ft), which can describe a height above a datum. Because the fathom is defined as exactly 6 ft, the same factor applies wherever the international foot (0.3048 m) is used.

Common mistakes

• Selecting the wrong direction. Entering 12.5 with the default fathoms-to-feet gives 75.00 ft, but if you actually meant 12.5 feet you should switch direction and get 2.08 fathoms.
• Multiplying when you should divide. Feet are the smaller unit, so the number of feet is always six times the number of fathoms, never one sixth.
• Confusing fathoms with metres. A fathom is 6 ft (about 1.83 m), so a 20 m depth is about 10.9 fathoms, not 20.
• Reading the depth on a chart without checking its unit. Charts are labelled in metres, feet or fathoms, and a number on a metric chart must not be typed in as fathoms.
• Using the rounded two-decimal answer to build a longer rope calculation. Convert the whole length at once instead of adding rounded pieces.