IALACOLREG
Academy

COLREG

Rule 12: Sailing Vessels

In a risk-of-collision approach between sailing vessels, COLREG decides who keeps out using the wind and windward side.

Rule 12 of 41

Decide

Two sailing vessels approach with risk of collision. Do you keep out of the way or stand on?

Tap a card and then its group, or drag it.

The rule in plain words

  1. Different sides?The vessel with the wind on the port side keeps out of the way of the other.
  2. Same side?The vessel to windward keeps out of the way of the vessel to leeward.
  3. Cannot tell the other's side?If you have wind on the port side, see the other vessel to windward and cannot determine her side with certainty, keep out of her way.
  4. What is the windward side?It is the side opposite to that on which the mainsail is carried; for a square-rigged vessel, opposite the side carrying the largest fore-and-aft sail.
Two sailing vessels in sight with risk of collision: A receives the wind on port, B on starboard, so A keeps out of B's way. Only projected courses are drawn. The overtaking rule remains an exception.
1 of 2

Before you read on: what would you do?

Question 1/1

When two sailing vessels have the wind on different sides, which vessel keeps out of the way?

Frequent mistakes

  • Wrong: "With different wind sides, neither vessel has priority."

    Right: The vessel with the wind on the port side keeps out of the way of the other.

  • Wrong: "With the same wind side, the leeward vessel keeps out."

    Right: The windward vessel keeps out of the way; the other vessel is to leeward.

  • Wrong: "If I cannot tell the other's side, I maintain my course."

    Right: With wind on port and the other vessel to windward, keep out when her side is uncertain.

Exam keys & interpretation

  1. "Different sides" does not mean port for both: identify which vessel has the wind on the port side.
  2. Same side: do not choose by port or starboard; first identify which vessel is to windward.
  3. Port wind + other vessel to windward + uncertainty activates paragraph (a)(iii): keep out.

How to read it

Read the rule in two steps: compare the wind sides; if they match, identify the windward and leeward vessels.

The windward definition avoids judging by appearance: check where the mainsail, or largest fore-and-aft sail, is carried.

Key points

  • Different sides → wind on port: keep out of the way.
  • Same side → windward vessel keeps clear of the leeward vessel.
  • Port wind + other vessel to windward + side uncertain → keep out.
  • Windward = opposite the mainsail; square-rigged → opposite the largest fore-and-aft sail.

Test your knowledge

3 questions to check it. Pick an answer to see why.

Question 1/3

When both sailing vessels have the wind on the same side, which vessel keeps out?

Now put it into practice40 questions with explained answers · no sign-up
Practise with the free test Follow the path through all 41 rules in the Academy. The first units are free.

Official text

IMO COLREG 1972 U.S. Coast Guard — International Navigation Rules (2024)

Full wording of the rule, reproduced from the official source below.

(a) When two sailing vessels are approaching one another, so as to involve risk of collision, one of them shall keep out of the way of the other as follows: (i) when each has the wind on a different side, the vessel which has the wind on the port side shall keep out of the way of the other; (ii) when both have the wind on the same side, the vessel which is to windward shall keep out of the way of the vessel which is to leeward; (iii) if a vessel with the wind on the port side sees a vessel to windward and cannot determine with certainty whether the other vessel has the wind on the port or on the starboard side, she shall keep out of the way of the other. (b) For the purposes of this Rule the windward side shall be deemed to be the side opposite to that on which the mainsail is carried or, in the case of a square-rigged vessel, the side opposite to that on which the largest fore-and-aft sail is carried.
Source:

More rules in this Part

More resources

Reviewed by Ramon Curto, Nautical teacher at IECNPC · Last reviewed:

Frequently asked questions about COLREG Rule 12

Which sailing vessel keeps out of the way when two sailing vessels meet?

When each has the wind on a different side, the vessel which has the wind on the port side shall keep out of the way of the other (Rule 12(a)(i)). In short, port tack gives way to starboard tack.

What happens when two sailing vessels have the wind on the same side?

The vessel which is windward shall keep out of the way of the vessel which is leeward (Rule 12(a)(ii)). Windward gives way to leeward whenever both vessels are on the same tack.

What if a sailing vessel cannot tell which tack the other is on?

If a vessel with the wind on the port side sees a vessel to windward and cannot determine with certainty whether that vessel has the wind on the port or on the starboard side, she shall keep out of the way of the other (Rule 12(a)(iii)).