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Rule 22: Visibility of Lights (COLREGS)

Last reviewed October 21, 2026

The short answer

Rule 22 sets minimum light ranges by vessel length. At 50 meters or more: masthead 6 miles, other lights 3 miles. From 12 to under 50 meters: masthead 5 miles (3 if under 20 meters), others 2 miles. Under 12 meters: masthead 2 miles, sidelights 1 mile, others 2 miles.

The rule text

a masthead light, 6 miles;

International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 22

a masthead light, 5 miles; except that where the length of the vessel is less than 20 meters, 3 miles;

International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 22

a sidelight, 1 mile;

International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 22

What it means on the water

  • 50 meters or more: masthead 6; sidelight, sternlight, towing light, all-round 3 (22(a)).
  • 12 to under 50 meters: masthead 5 (3 if under 20 meters); others 2 (22(b)).
  • Under 12 meters: masthead 2, sidelight 1, sternlight 2, towing 2, all-round 2 (22(c)).
  • Inconspicuous, partly submerged towed objects: white all-round light, 3 miles (22(d)).

International vs Inland

Inland adds the special flashing light, 2 miles in every size class. Otherwise the ranges match.

Common exam traps

  • Giving a 15-meter vessel a 5-mile masthead light. Under 20 meters it's 3 miles.
  • Giving small-boat sternlights 1 mile. Only the sidelight is 1 mile.

Try 3 questions on Rule 22

  1. Minimum masthead light range on a 60-meter vessel?

    1. 3 miles
    2. 5 miles
    3. 6 miles
    4. 2 miles
    Show answer

    C. 6 miles Rule 22(a).

  2. Sidelight range on a 10-meter vessel?

    1. 1 mile
    2. 2 miles
    3. 3 miles
    4. 0.5 mile
    Show answer

    A. 1 mile Rule 22(c).

  3. Masthead light range on an 18-meter vessel?

    1. 2 miles
    2. 3 miles
    3. 5 miles
    4. 6 miles
    Show answer

    B. 3 miles Rule 22(b).

Frequently asked questions

What is the range of a sternlight?

3 miles at 50 meters or more, otherwise 2 miles (Rule 22).

Which light has the longest range?

The masthead light on a vessel 50 meters or more: 6 miles.

Does Inland add anything?

Yes, the special flashing light at 2 miles.

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