A cable length, often shortened to cable, is a nautical unit of distance. In modern international use it is normally treated as one tenth of a nautical mile.
Because the unit grew out of practical seamanship rather than a single universal statute, older sources may use different values. That is why cable lengths should be interpreted carefully when reading historical charts or naval records.
The modern international value
1 international cable = 0.1 international nautical mile
1 international cable = 185.2 meters
10 international cables = 1 international nautical mile
The modern international nautical mile is exactly 1,852 meters, so a tenth of that distance is exactly 185.2 meters. This is the simplest value to use for modern conversions unless a chart, table or source specifies another standard.
Why it is called a cable
The name comes from the ship’s anchor cable: the heavy rope, and later chain, used to hold a vessel at anchor. In older seamanship, “a cable’s length” was a practical expression before it became a more formal unit.
A traditional cable was often associated with about 100 fathoms, or roughly 600 feet. Since a fathom is 6 feet, this made the cable convenient in the same measurement family as sounding lines and nautical miles.
International, British and U.S. values
The exact value of a cable is not always the same in historical material. The international cable is one tenth of the modern international nautical mile. Older British and U.S. naval usage could differ.
| Usage | Value | Approximate metric value |
|---|---|---|
| International cable | 0.1 international nautical mile | 185.2 m |
| Traditional cable | 100 fathoms / 600 ft | 182.88 m |
| British naval cable | 608 ft | 185.3184 m |
| U.S. naval cable | 120 fathoms / 720 ft | 219.456 m |
This variation is small in some cases and large in others. For modern work, use the international value unless the source explicitly says otherwise. For historical research, the country, date and chart legend matter.
How cables relate to fathoms and nautical miles
Nautical units form a practical chain. The nautical mile is useful for chart distances and speed through knots. The fathom is useful for depth. The cable sits between them as a short horizontal distance at sea.
1 nautical mile = 10 international cables
1 international cable = 185.2 meters
1 standard fathom = 6 feet = 1.8288 meters
The close relationship between these units is one reason they appear together in old maritime texts, naval documents and hydrographic notes.
When the unit matters
For casual reading, “a cable” usually means a short distance at sea. For precise conversion, however, the definition must be known. This is especially important in:
- historical chart interpretation;
- shipwreck location research;
- naval reports and gunnery ranges;
- anchorage descriptions and coastal pilotage notes.