GearPort
Anchor light rules: what a boat must show at anchor
An anchored boat at night shows one thing: a white light visible from every direction. The rule that says so is Rule 30 of the Navigation Rules, it is short, and almost every question about anchor lights is answered by reading it for your boat's size.
The text below follows the US Inland Rules, which for anchor lights match the international rules on everything a recreational boat cares about, with one extra exemption for designated anchorage areas that exists only in US waters.
The rule, by vessel size
A vessel at anchor exhibits, where it can best be seen, an all-round white light: a light showing over the full 360 degrees. During the day the equivalent signal is a single black ball shape hung in the fore part of the boat.
A vessel of less than 50 meters, which is about 164 feet and covers every recreational boat, may show one all-round white light where it can best be seen instead of the two-light arrangement required of big ships. One light, visible all round, positioned so nothing blocks it. That is the whole requirement.
A vessel of 50 meters or more shows two all-round white lights, one forward and one at or near the stern set lower. A vessel of 100 meters or more must also light up her decks. If you see a ship lit like a small town at anchor, that is why.
For visibility range, the rules require an all-round light on a vessel under 50 meters to be visible at 2 nautical miles, which is why anchor lights are sold with a 2NM rating.
The two exemptions
A vessel of less than 7 meters, about 23 feet, is not required to show an anchor light provided it is anchored away from a narrow channel, a fairway, an anchorage, and anywhere other vessels normally navigate. Read that condition honestly: a 20 foot boat anchored at the edge of a busy creek is exactly where other boats navigate, and the exemption does not apply.
In US waters only, a vessel of less than 20 meters anchored inside a special anchorage area designated by the Coast Guard needs no anchor light at all. Special anchorages are marked on charts, and many mooring fields are designated ones. If you cannot point to the designation on a chart, assume it does not exist.
Neither exemption ever makes a light a bad idea. The rule sets the floor, and an unlit boat on a dark night is relying entirely on other people's radar and luck.
Which light on the boat is the anchor light
On most small powerboats the anchor light is the all-round white pole light at the stern, the same light used under way in combination with the sidelights. At anchor the sidelights go off and the all-round white stays on. If your switch panel has separate NAV and ANC positions, that is exactly the distinction they encode.
On sailboats the anchor light is usually at the top of the mast: an all-round white fitting, distinct from the masthead steaming light, which only covers 225 degrees and does not satisfy the rule.
A masthead light is not an anchor light. It shows white over 225 degrees, and the missing 135 degrees astern is precisely what an approaching boat behind you would need to see.
Buying and running one
Buy the rating, not the brightness. A 2NM-rated all-round white light meets the requirement for any vessel under 50 meters. How bright it looks on a shelf tells you nothing about certified range.
Mount it above obstructions. An all-round light blocked by a T-top, a radar arch or a flag is no longer showing 360 degrees. Pole lights come in different heights for a reason, and fold-down or plug-in bases let a tall pole stow flat when running.
Mind the battery. An anchor light runs all night by definition. An LED fitting draws a fraction of an incandescent one over those hours, which on a small battery bank is the difference between starting in the morning and not.
Check it actually works from every side. Walk around the boat, or dinghy around it once. Anything that shadows the light is a problem you want to find before the night it matters.
All-round and anchor lights
2NM all-round white lights, fold-down and plug-in pole lights and bases, and LED anchor lights from Attwood, Perko, Hella Marine and Lumitec.
Common questions
- What light does a boat need at anchor?
- An all-round white light, visible over 360 degrees, displayed where it can best be seen. Any vessel under 50 meters, which is every recreational boat, meets the rule with one such light. The daytime equivalent is a single black ball shape.
- What lights must a 12 meter boat display when anchored at night?
- One all-round white light where it can best be seen. A 12 meter boat is under the 50 meter threshold, so a single 360 degree white light satisfies Rule 30. The under-7-meter exemption does not apply to a boat that size.
- Do I need an anchor light on a small boat?
- A boat under 7 meters anchored well away from channels, fairways, anchorages and anywhere vessels normally navigate is not required to show one. Anchored anywhere near traffic, yes. And in US waters a boat under 20 meters in a Coast Guard designated special anchorage area is exempt regardless.
- How far must an anchor light be visible?
- For a vessel under 50 meters the rules require the all-round white light to be visible at 2 nautical miles, which is what the 2NM rating on a fitting certifies.
- Is the masthead light the same as an anchor light?
- No. A masthead light covers 225 degrees and is shown by power-driven vessels under way. An anchor light covers the full 360 degrees. On sailboats the anchor light is a separate all-round fitting, usually at the top of the mast.
- Can I use my all-round stern pole light as the anchor light?
- Yes. On small powerboats that is the standard arrangement: under way it works with the sidelights, and at anchor it stays on alone with the sidelights off.