Convert Fathom to Inch (ftm → in)

The fathom is the traditional marine depth unit, equal to six feet, used in nautical charts and diving manuals.

Fathom

Inch

1 ftm72 inNIST · BIPM accuracy

Fathom to Inch Conversion Table

10 common values

Fathom	Inch
1 ftm	72 in
5 ftm	360 in
10 ftm	720 in
25 ftm	1,800 in
50 ftm	3,600 in
100 ftm	7,200 in
250 ftm	18,000 in
500 ftm	36,000 in
1,000 ftm	72,000 in
5,000 ftm	360,000 in

How to Convert Fathom to Inch Manually

Step by Step

Converting fathoms to inches is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1
Take your value in fathoms
Start with the number of fathoms (ftm) you want to convert.
2
Multiply by 72
The conversion factor from ftm to in is 72. Multiply your value by this number.
3
Read the result in inches
The result is your value in inches (in).

Practical Examples

1 ftm

equals

72 in

5 ftm

equals

360 in

10 ftm

equals

720 in

25 ftm

equals

1,800 in

100 ftm

equals

7,200 in

Formula

Multiply the value in fathoms by 72. For the reverse direction, multiply by 0.013889.

Forwardin = ftm × 72

Reverseftm = in × 0.013889

Example: 10 ftm × 72 = 720 in

Tips

Use these in everyday conversions

1 fathom = 2 yards = 6 feet = 1.8288 m.
Modern charts use metres internationally; fathoms are mostly historical.
The word "fathom" comes from Old English for "outstretched arms" — originally the span of an adult's arms.

Common Mistakes

Avoid these

Reading a modern chart that uses metres as if it were fathoms — a factor-of-1.83 depth error.
Confusing fathoms with feet on mixed-unit charts.
Assuming all US charts still use fathoms — NOAA has largely migrated to metres.

About Fathom and Inch

What is the Fathom?

The fathom equals exactly 1.8288 meters or 6 feet and is the traditional marine depth unit. The word derives from the Old English 'fæðm,' meaning the span of outstretched arms — historically the distance a sailor could measure rope by stretching it from fingertip to fingertip. Used since antiquity for sounding water depth (lowering a weighted line and counting fathom marks), the fathom remains common in nautical charts, diving manuals, and marine literature. Famous from Mark Twain's pen name (a riverboat lead's call meaning 'safe water,' 2 fathoms or 12 feet) and Shakespeare's 'full fathom five,' the unit retains cultural resonance. Modern oceanographic science prefers the meter, but the fathom persists in fishing, recreational diving, and historical maritime contexts. The fathom relates to the foot (1 fathom = 6 ft) and the yard (1 fathom = 2 yd).

Water depth on older US nautical charts
Maritime literature and historical navigation
Sport diving and scuba depth references in the US

Real-world examples

A "mark twain" reading — made famous by the Mississippi riverboats — meant 2 fathoms (3.66 m) of water, the minimum safe depth.

What is the Inch?

The inch equals exactly 25.4 millimeters under the 1959 international yard and pound agreement. The word derives from the Old English 'ynce,' from Latin 'uncia' meaning one twelfth (the inch is one twelfth of a foot). Originally based on the width of a thumb, the inch has been standardized for centuries. It is the global standard for screen sizes (a 15-inch laptop or 65-inch TV), pipe and tubing diameters (1-inch plumbing, 2-inch exhaust), and shoe sizes in Anglo-Saxon countries. Construction lumber, photographic prints, paper sizes (US Letter is 8.5 × 11 in), and rainfall in the US all use inches. The inch relates to the millimeter (25.4 mm = 1 in exactly), the foot (12 in = 1 ft), and the yard (36 in = 1 yd). Subdivisions in fractions (½, ¼, ⅛) remain common in carpentry.