Cable length

A cable length or length of cable is a nautical unit of measure equal to one tenth of a nautical mile or approximately 100 fathoms. Owing to anachronisms and varying techniques of measurement, a cable length can be anywhere from 169 to 220 metres (185 to 241 yd), depending on the standard used.

cable length
A chain cable. A cable length is based on the historic length of a ship's cable.
General information
Unit system	Imperial/US units
Unit of	Length
Conversions
1 cable length in ...	... is equal to ...
Imperial/US units	0.1 NM
Metric (SI) units	185.2 m
Conversions (imperial)
1 imp unit in ...	... is equal to ...
Imperial/US units	100 fathoms 600 ft
Metric (SI) units	182.9 m
Conversions (US)
1 US unit in ...	... is equal to ...
Imperial/US units	120 fathoms 720 ft
Metric (SI) units	219.5 m

Etymology and origin

The modern word cable is directly descended from the Middle English cable, cabel or kabel and also occurs in Middle Dutch and Middle German. Ultimately the word comes from Romanic, probably from a cattle halter.^[1] A cable in this usage cable is a thick rope or by transference a chain cable.^[1] The OED gives quotations from c. 1400 onwards. A cable's length (often "cable length" or just "cable") is simply the standard length in which cables came, which by 1555 had settled to around 100 fathoms (600 ft; 180 m) or 1⁄10 nautical mile (0.19 km; 0.12 mi).^[1]

Traditionally rope is made on long ropewalks, the length of which determines the maximum length of rope it is possible to make. As rope is "closed" (the final stage in manufacture) the length reduces, thus the ropewalk at Chatham Dockyard is 1⁄4 mile (0.40 km) long in order to produce standard 220 metres (120 fathoms) coils.^[2]

Definition

The definition varies:

• International: 185.2 m, equivalent to 1⁄10 nautical mile
• UK traditional: 100 fathoms (600 ft; 180 m), though (The Admiralty) used 1⁄10 of a sea mile, 1 minute of latitude locally.
• US customary (US Navy): 120 fathoms (720 ft; 220 m)^[3]

In 2008 the Royal Navy in a handbook defined it as

A cable equals one-tenth of a sea mile - 608 ft. The length of a ship's hempen anchor cable was formerly 101 fathoms. 100 fathoms = 1 cable 10 cables = 1 nautical mile (very nearly)^[4]

References

1. OED-cable.
2. Master Ropemakers Ltd 2023.
3. Fenna 2002.
4. Royal Navy 2007.

Citations

• Fenna, Donald (2002), "cable, cable length, cable's length", A Dictionary of Weights, Measures, and Units, Oxford: Oxford University Press, p. 35, ISBN 0-19-860522-6, OCLC 62608533, retrieved 12 January 2017. Also "fathom", from the same work (pp. 88–89, retrieved 12 January 2017).
• Master Ropemakers Ltd (2023), "Showing you the ropes", Historic Dockyard Chatham, retrieved 20 December 2023 Various subpages within the ropery section.
• "cable". Oxford English Dictionary (Online ed.). Oxford University Press. doi:10.1093/OED/2955013352. (Subscription or participating institution membership required.)
• Royal Navy (2007), Navy Slang: Cable – Curry, Royal Navy, archived from the original on 2008-07-07, retrieved 1 February 2011.