How to run a tournament with an odd number of players

Why an odd field is awkward in the first place

There are only two places an awkward number actually bites, and it helps to separate them.

A round robin needs an even number of players to fill every table in a round. With an odd number, exactly one player sits out each round. That is a bye, it rotates through the field, and it is a property of the format rather than a mistake you made.

A knockout needs the field to be a power of two — 2, 4, 8, 16, 32 — or the first round cannot pair up cleanly. Any other number has to be padded up to the next power of two, which is the second kind of bye and the one people mean when they ask about odd numbers.

Everything else — 13 players into 4 groups, 21 into 6 — is not really a problem at all. It only feels like one because the instinct is to make the groups equal, when what you want is groups that are near-equal.

Step 1: choose the group count, then balance the sizes

The working size for a club night is groups of three or four. Three is the smallest group that still gives everyone more than one match. Five starts to drag, because a group of five is ten matches before anybody reaches a knockout.

So divide the field by four and round up. That is your group count. Then deal the players out so that no group is more than one player bigger than any other: take the remainder and hand one extra player to that many groups.

Two guard rails. Never leave a group of one, because a single player has nobody to play. And below about six players, stop splitting altogether — a field of five is a better night as one round robin of ten matches than as a three and a two.

• Group count = players divided by four, rounded up.
• Group sizes = players divided by that group count, with the remainder handed out one extra player at a time, so sizes never differ by more than one.
• Matches inside a group of n = n x (n - 1) / 2. A group of three is 3 matches, a four is 6, a five is 10.
• Seed across the groups in snake order, so the group that ends up one player short is not also the group with all the strong players in it.

Worked splits for every field from 5 to 24 players

Apply the rule above and there is exactly one sensible split for each field size. Read the row for your number: how many groups, the size of each, and how many matches the group stage costs you. A knockout stage on top adds roughly one match for every player eliminated.

These are also the splits PingPong Arena produces, and each row below was checked against the code that builds the draw rather than worked out on paper.

Step 2: how byes actually work

A bye is an empty slot in the draw. It is how a field that is not a power of two gets stretched to one.

Say eleven players come out of the groups into a knockout. The next power of two above eleven is sixteen, so the bracket is built for sixteen slots and five of them are filled with nothing. A player drawn against an empty slot does not play: they are credited the win and walk into round two. Five players get a free first round, the other six play three matches to join them, and round two has a clean eight.

Two conventions make byes fair rather than a lottery. Give them to the top seeds first, so the players skipping round one are the ones whose round-one match nobody needed to see. And spread them across the bracket rather than stacking them in one half, or one side arrives at the semi-finals fresh and the other has played twice.

The arithmetic to check is one subtraction: byes = the next power of two, minus your players.

• 5 players go into an 8-slot bracket — 3 byes
• 6 players into 8 slots — 2 byes
• 7 players into 8 slots — 1 bye
• 9 players into 16 slots — 7 byes
• 11 players into 16 slots — 5 byes
• 12 players into 16 slots — 4 byes
• 14 players into 16 slots — 2 byes
• 17 players into 32 slots — 15 byes, which is the signal that 17 is a poor field to send straight into a knockout and a much better one to put into groups first
• 20 players into 32 slots — 12 byes
• 24 players into 32 slots — 8 byes

The part that actually ruins the night: tables

Uneven groups are not really a fairness problem. They are a timing problem, and that is the one organisers actually live through.

Take sixteen players split 8, 4 and 4. The eight-player group has twenty-eight matches to get through; each group of four has six. Give every group one table and treat them as equals, and the two small groups are done inside the hour while the big group is barely half finished. Everybody else stands around watching, and the knockout cannot start until the last group is in.

The fix is to stop handing out tables per group and start handing them out per remaining workload. Deal the tables one at a time, and each time, give the next free table to whichever group has the highest ratio of unfinished matches to tables it already holds. The eight-player group scores 28 divided by 1, against the small groups' 6 divided by 1, so it takes the first table. Holding two tables it scores 14, holding three it scores about 9.3 — still ahead, so it keeps taking tables until its backlog per table falls to the small groups' level. As it burns down, the tables move across.

One natural limit keeps this honest: a group can only use as many tables as it can fill with players who are not already playing. Eight players can occupy at most four tables at once, so a fifth table goes to a small group whatever the arithmetic says.

You can run this on a whiteboard and it works. PingPong Arena applies it every time a table frees up, which is why an 8/4/4 split finishes at roughly the same time in all three groups rather than leaving one group still playing while everyone waits. It shipped after a real club night on 13 August 2026 where a 7/6/6 split left one group idle for a full round.

Keep the players in the small groups playing

The other cost of an awkward field is that the exits are uneven too. A player in a group of three can be out of the whole event after two matches, while the group of four next to them is still going.

So give the lower finishers somewhere to go. Below the qualifiers there is usually room for a second knockout, a consolation, and below that a third — so the players who finished at the bottom of their group get a bracket of their own instead of an early night and a long walk to the car.

PingPong Arena builds that third tier as a placement bracket: everyone below the consolation cut-off in each group is drawn into their own knockout. At the top of the event, turning on the single bronze medal setting adds a bronze match whenever there are three or more finalists, so third place is played for rather than shared.