What is the mark zone in sailing?

The zone is the area within three hull lengths of the mark, measured by the hull length of whichever boat is nearer to it. The situation at the moment the first boat reaches the zone, whether the boats are overlapped and which is inside, decides who is entitled to mark-room.

What is mark room in sailing?

Mark-room is the room a boat needs to sail to the mark when its proper course is close to it, to round or pass the mark on the required side, and to leave it astern. It does not include a general right to room to tack.

How far is the zone around a sailing mark?

Three hull lengths, measured from the mark using the length of whichever of the two boats is nearer to it. For a six-metre boat that is about 18 metres.

What is an overlap in sailing racing?

An overlap exists when neither boat is entirely ahead of or behind the other. As long as any part of a boat or its equipment in its normal position is alongside any part of the other boat, the boats are overlapped.

Room at the mark: how Rule 18 works

When two or more boats converge on a mark, Rule 18 of the Racing Rules of Sailing decides who must give way and what "room" means. The test turns on one moment: the situation between the boats when the first of them reaches the zone.

The zone

The zone is the area within three hull lengths of the mark. The distance is measured using the hull length of whichever of the two boats is nearer to the mark, so it is not a fixed circle. It is usually pictured as a circle about three boat-lengths across, which is close enough for most racing.

Rule 18 applies between boats that must leave a mark on the same side once at least one of them is in the zone. It does not apply between boats on opposite tacks on a beat to windward, or between a boat approaching the mark and one leaving it.

Who must give mark-room

Everything hinges on the moment the first boat reaches the zone:

If the boats are overlapped, the outside boat must give the inside boat mark-room. The inside boat is the one between the mark and the outside boat.
If the boats are not overlapped, the boat that reached the zone first is entitled to mark-room, and the boat still outside the zone must give it. This holds even if the boat that got there first is clear astern of the other.

That second point changed in the 2025-2028 rules. It used to be that the boat clear ahead at the zone was entitled to room; now it is simply whichever boat reaches the zone first. The practical effect can be surprising: imagine two boats not overlapped, with the trailing boat slightly closer to the mark and crossing into the zone a moment before the boat ahead of her. Under the current rule the trailing boat reached the zone first, so she is entitled to mark-room and the boat clear ahead must give it, even though she is the one in front.

Entitlement is fixed at the zone, mostly

Once mark-room is owed, it stays owed even if the overlap later breaks or a new overlap forms. A boat that has to give mark-room keeps giving it for as long as Rule 18 applies.

There are limits. The entitlement set at the zone (Rule 18.2(a)) no longer applies if the boat entitled to mark-room leaves the zone or passes head to wind. That does not necessarily end mark-room altogether: if the boats are still overlapped at that point, Rule 18.2(c) takes over and the outside boat must give the inside boat mark-room on the new basis. The separate rules for tacking (Rule 18.3) and gybing (Rule 18.4) in the zone can also change the picture, as below.

What mark-room means

Mark-room is the room a boat needs to:

sail to the mark, when its proper course is to sail close to it,
round or pass the mark on the required side, and
leave the mark astern.

It is room to get round, not a licence to take more space than rounding needs. A boat entitled to mark-room must sail within that room and cannot use it to interfere with the outside boat beyond what the rounding requires. Mark-room does not include a general right to room to tack.

The starting mark exception

Rule 18 does not apply at a starting mark surrounded by navigable water when boats are approaching to start. A leeward boat cannot claim mark-room from a windward boat to win a better slot on the line. The normal port-starboard and windward-leeward rules govern the start instead.

Tacking in the zone (Rule 18.3)

Tacking near a mark has its own rule. If a boat passes head to wind from port to starboard tack in the zone of a mark left to port, Rule 18.2 does not apply between it and a boat on starboard tack that is fetching the mark. The boat that tacked must not force the starboard-tack boat to sail above close-hauled, and must give it mark-room if it becomes overlapped inside. So tacking inside the zone does not manufacture a right to room against a boat already fetching the mark on starboard.

Gybing in the zone (Rule 18.4)

When an inside overlapped right-of-way boat must gybe to sail its proper course, it shall sail no farther from the mark than it needs to in order to gybe and sail that course. It cannot use its rights to swing wide and carry the outside boat away from the mark. Rule 18.4 does not apply at a gate mark.

Leeward mark versus windward mark

At the leeward mark, boats usually converge from downwind on the same gybe. The deciding question is the overlap at the zone: an inside-overlapped boat gets mark-room, and where there is no overlap, the boat that reached the zone first does. Disputes often come from a boat trying to grab an inside overlap right at the boundary.

At the windward mark, boats are on a beat. Between boats on opposite tacks beating to the mark, Rule 18 does not apply at all, so port and starboard governs the approach. Rule 18 comes into play once the boats are on the same tack or one of them is rounding, and Rule 18.3 covers a boat that tacks onto starboard in the zone.

At any mark, start from the same question: when the first boat reached the zone, were the boats overlapped, and if so which was inside, or if not, which boat got there first?

Last updated: 2026-06-15