Sevens is simple on the scoreboard: seven players, huge space, no spare bodies.

How many players are on the field

Each side has seven players in the playing area during play. That is the central team-size rule in sevens and the reason the format looks so open: the teams use a full rugby field with less than half the normal 15-a-side personnel.

The rule is a maximum, not a licence to add a specialist extra player for attack, defence, kicking, or scrums. If a team has an eighth active player on the field, the referee can require the captain to reduce the number and may apply the law for too many players or illegal entry.

How many replacements are allowed

World Rugby's sevens variation to Law 3 allows a team to nominate and use up to five replacements. For non-international or locally organised matches, the match organiser decides the number that may be nominated, but the sevens variation still caps that number at five.

This is separate from a tournament squad. An event may have its own rules for how many players a team can register for the weekend, how injury replacements are approved, when lists are submitted, and who is eligible for each match. The match-day law controls the players and replacements for a single game.

What the seven positions usually are

Sevens teams are commonly described as three forwards and four backs. At scrum time, the three forwards form the scrum. The other four players provide the passing, kicking, support running, and defensive coverage outside the scrum.

The laws do not require every sevens player to fit a fixed job title in open play. Teams may use different labels such as prop, hooker, scrum-half, playmaker, centre, wing, or sweeper, but the practical demand is wider: every player must tackle, pass, support, defend space, and handle repeated high-speed efforts.

Why three forwards matter

A sevens scrum has three players from each team, and all three must stay bound until the scrum ends. In ordinary rugby language those players are the front row: two props and a hooker.

That does not make sevens a forward-heavy game. Because only three players are tied into the scrum, four defenders remain outside to cover a large field. Clean scrum ball can create immediate attacking space, which is why the connection between team size and sevens scrum rules is so important.

Shirt numbers are not the whole story

Viewers should be careful about reading sevens positions from shirt numbers alone. Competition regulations may control squad numbering, but the rugby laws do not make sevens positions as rigid as a 15-a-side team sheet with numbers one through fifteen.

A starting seven can be selected for pace, ball-winning, restart skill, defensive range, or kicking ability. The bench can also be built around tournament needs rather than a simple one-for-one position chart.

Replacements do not mean rolling rotation

Having up to five replacements does not automatically mean unlimited interchange. Normal replacements are made only when the ball is dead and only with the referee's permission. A player who leaves tactically is not free to return whenever the coach wants another burst of speed.

Some competitions may use specific local or modified replacement procedures at defined levels, but readers should not assume those apply to standard World Rugby sevens. For the general rule, use the replacement law first and the competition regulations second.

Sanctions can change the numbers

A team may start with seven players, but cards can reduce that number. A yellow card in sevens sends the player to the sin bin for two minutes, and the team plays short during that period. It cannot cancel the suspension by sending on a replacement for the carded player.

A red card removes the player from the match. Replacement after a sending off depends on the law and any elite or competition-specific red-card variation in force, so it should not be assumed in ordinary sevens explanation. The immediate match effect is that the carded player is gone and officials manage the team numbers from there.

What happens if a team has eight

If a team has too many players in the playing area, the referee can order the captain to reduce the number. If the issue is raised as an objection under Law 3, the score at that time remains unchanged, but the sanction can be a penalty.

Officials also look at unauthorised entry. If a replacement or returning player joins without the referee's permission and the referee believes it was done to gain an advantage, the player is guilty of misconduct and the sanction can be a penalty.

Where viewers get caught

• "Sevens has seven starters and five substitutes, so the squad is always twelve": not exactly. That describes the match replacement limit in many sevens contexts, but event-squad registration can be set by tournament rules.
• "Three forwards means only three players defend physically": no. Every sevens player must tackle, contest space, and support at the breakdown.
• "The positions work like 15s with eight players removed": no. Sevens roles are more fluid because there are fewer set-piece specialists and much more open-field space.
• "A yellow card can be covered by the bench": no. The team plays with fewer players while the suspension is active.
• "An extra player is harmless if the ball is elsewhere": not necessarily. The referee judges entry, permission, numbers, and whether the team gained an advantage.

How officials manage team size

1. Check that each team has no more than seven players active in the playing area.
2. Confirm any replacement is eligible under the match list and competition rules.
3. Allow replacements only when the ball is dead and the referee or appointed official has permitted the change.
4. Track yellow cards, red cards, injuries, blood replacements, and any temporary replacement process.
5. At scrums, ensure exactly three players from each team bind and stay bound until the scrum ends.
6. If too many players or unauthorised entry affects play, apply the appropriate penalty or misconduct process.

Source material

• World Rugby Sevens variation: Law 3 Team
• World Rugby Law 3: Team
• World Rugby Sevens variation: Law 19 Scrum
• World Rugby Laws of the Game