Round robin group generator for any group size
Pair tournaments have a familiar rotation. Groups of three, four, or more are different: each group creates several pairwise contacts at once, and arithmetic can rule out a perfect design before a solver starts.
Guide visual
Round robin groups
Everyone-meets-everyone when the math allows it.
Passing the arithmetic is not an existence proof
These conditions can reject impossible requests, but they do not guarantee that a combinatorial design exists for every remaining parameter set. Fixed hosts, balancing goals, keep-apart requirements, and uneven attendance narrow the solution space further.
Treat a perfect result as something to verify in the generated schedule, not something implied by a clean division.
Choose round robin settings honestly
Fix N and G
Count actual participants and decide whether equal group size is mandatory. Record any planned byes or uneven group explicitly.
Check the requested horizon
Use R × (G − 1) ≤ N − 1 to see whether no repeats are even possible.
Check full-coverage arithmetic
If everyone must meet everyone once, calculate (N − 1) / (G − 1) and verify equal-group divisibility.
Generate without extra rules first
Establish whether the basic shape can be solved before adding hosts, balance, or relationship constraints.
Add requirements one at a time
After each addition, compare validity, repeat count, and concentration with the simpler schedule.
Choose an explicit compromise
When perfection is unavailable, reduce rounds, change group size, allow uneven groups, add a bye, or accept a clearly labeled best-effort result.
One exact target and one impossible target
Exact round robin has a visible signature
- Your groups confirms the schedule shape: every attending participant appears once per round and every group has the intended size.
- For exact everyone-meets-everyone-once coverage, every possible pair belongs in the histogram’s “1 shared session” bucket. The never-met and repeated totals must both be zero.
- Any matrix cell with zero meetings or more than one meeting identifies the exact pair that breaks full coverage and the sessions involved.
- Required fixed placements and required relationship rules remain solver invariants after they are added. Their compliance cards report “No violations” in a valid result; otherwise the result exposes a solver defect.
- Keeping the exact unconstrained result provides a useful baseline: its histogram and matrix can be compared directly with the constrained version.
Inspect the exact setup and result
Use the example’s explicit handoff for its 16-person scenario. Product links navigate within the current scenario; the Help topic explains Results evidence.
Worked example: sixteen people in groups of four
Five rounds give every person fifteen contact slots, exactly matching the other fifteen participants. Four equal groups fit each round. The target is exact coverage: every unordered pair should appear once.
Setup facts
- 16 participants
- 4 groups of 4
- 5 rounds
- 120 distinct participant pairs to cover
Review the result
- Confirm every person appears once in each round.
- Confirm every pair meets exactly once, not merely that the total repeat score is low.
- Add constraints only after preserving a copy of the exact unconstrained result.
Try this setup in GroupMixer
This tool is preloaded with the example from this guide. You can edit the participants, constraints, sessions, and balance settings before generating groups.