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A Cable Length (symbol cb), often shortened to cable, is a nautical unit of length, traditionally related to the length of a ship's anchor cable. While its exact length has varied historically and geographically, it is now most commonly defined internationally as one-tenth of a nautical mile (1/10 NM).

This standard definition equates to:

• 185.2 meters (m)
• Approximately 607.61 feet (ft)
• Approximately 202.54 yards (yd)

Other historical definitions based on the fathom also exist.

The unit originated from the practical length of a ship's anchor cable (or "shot" of chain) used in the age of sail. Anchor cables were typically manufactured in standard lengths that could be shackled together. This length provided a convenient unit for measuring distances related to anchoring and maneuvering close to shore or other vessels.

However, the length was not universally standardized:

• In the British Royal Navy, a cable was traditionally defined as 100 fathoms (equivalent to 600 feet or 182.88 meters).
• In the U.S. Navy, it was often defined as 120 fathoms (equivalent to 720 feet or 219.456 meters).

With the international adoption of the nautical mile (defined as 1852 meters), defining the cable as exactly one-tenth of this value (185.2 m) created a convenient, decimal-based relationship and became the most common modern standard, sometimes referred to as the "international cable length".

The cable length, particularly the 1/10 NM definition, remains in use in specific maritime contexts:

• Nautical Navigation & Ship Handling: Measuring short distances at sea, such as the distance between ships in formation, distance off a navigational hazard, distance to a pier, estimating anchor drag, or describing the scope (length) of anchor cable paid out.
• Hydrographic Surveying: Historically used on nautical charts, although meters are now the primary international standard for depth and short distances on modern charts.
• Naval Terminology: Persists in naval traditions and communications for describing close ranges.
• Historical Context: Encountered in older maritime texts, logs, charts, and naval records.