The fathom, unit of length
The fathom is exactly 1.8288 meters, that is six feet. It was the unit of sounding, the depth of water under a keel, and its name comes from the Old English for the span of a man's outstretched arms.
It named a writer. On the Mississippi the leadsman called the depth aloud as he hauled the sounding line, and the call for two fathoms, twelve feet, was mark twain: the shallowest water in which a steamboat could still pass. Samuel Clemens, who had piloted those boats, took the call as his pen name in 1863. The unit itself has retreated since: charts are drawn in meters today, and the fathom survives mostly in older editions and in the language of the sea.
The fathom in other units
| 1 ftm | 0.0018288 km |
| 1 ftm | 1.8288 m |
| 1 ftm | 182.88 cm |
| 1 ftm | 1,829 mm |
| 1 ftm | 0.00113636 mi |
| 1 ftm | 2 yd |
| 1 ftm | 6 ft |
| 1 ftm | 72 in |
| 1 ftm | 0.000987473 nmi |
| 1 ftm | 18.288 dm |
| 1 ftm | 1,828,800 µm |
| 1 ftm | 6.03504 shaku |
| 1 ftm | 60.3504 sun |
| 1 ftm | 1.00584 ken |
| 1 ftm | 0.000465667 ri |
Frequently asked questions
How many feet are in a fathom?
Six exactly, which is 1.8288 meters. The figure is exact because the foot has been exactly 0.3048 meters since 1959, so the fathom carries no approximation of its own.
Why measure depth in fathoms rather than feet?
Because the sounding line was hauled in by arm spans, and a fathom is one span. The leadsman counted his own reach rather than reading a scale, which is why the unit is the length of a man and not a fraction of anything.
Are nautical charts still in fathoms?
Rarely. Hydrographic offices moved to meters, and a modern chart gives depths in meters and tenths. Older charts and older sailors keep the fathom, so a depth quoted without its unit is worth checking before trusting it.