Round-Robin Pair Scheduler (Tournament & 1-on-1 Rotation)
When you have N people who all need to pair up across multiple rounds — peer code review buddies, debate tournament matches, sparring partners, 1-on-1 mentoring rotations, hackathon icebreakers, board-game ladders — the question is the same: how do you guarantee everyone meets everyone exactly once, with the fewest rounds possible? The answer is the round-robin schedule, and the classic construction is the circle method: fix one participant, rotate the rest around them, and read off pairs across a diameter. For N participants (N even), this produces N-1 rounds of N/2 simultaneous pairings each, covering all N(N-1)/2 unique pairs exactly once. When N is odd, a phantom Bye slot is added so someone rests each round. This tool runs the construction directly: paste your names, get a complete round-by-round table and a per-person view showing who each participant meets in each round. Initial order can be alphabetical (reproducible) or randomized with a seed (re-roll to see different layouts). Nothing leaves your browser.
- Match 1Eve↔Dave
- Match 2Bob↔Alice
- Match 3Frank↔Carol
- Match 1Eve↔Alice
- Match 2Dave↔Carol
- Match 3Bob↔Frank
- Match 1Eve↔Carol
- Match 2Alice↔Frank
- Match 3Dave↔Bob
- Match 1Eve↔Frank
- Match 2Carol↔Bob
- Match 3Alice↔Dave
- Match 1Eve↔Bob
- Match 2Frank↔Dave
- Match 3Carol↔Alice
Classic circle method: fix one participant, rotate the rest clockwise around them, and pair across the diameter. N (even) participants produce N-1 rounds of N/2 matches, covering all C(N,2) unique pairs exactly once. Computation is local — no participant names leave your browser.
How to use
- Paste participant names — one per line, or comma-separated.
- Choose alphabetical order (reproducible) or random (seeded — re-roll for new layouts).
- Toggle between 'by round' and 'by person' views.
- Odd participant counts get a (Bye) slot — that person rests for one round.
- Use 'Copy as Markdown' to drop the full schedule into a doc or PR description.
Frequently asked questions
- What's the circle method?
- Lay out N participants around a circle. Fix participant 1 in place. For each round, draw a chord across the diameter — pairs are (1, N), (2, N-1), (3, N-2), and so on. Then rotate everyone except participant 1 clockwise by one position and repeat. After N-1 rounds, every pair has met exactly once. It's the standard construction taught in tournament scheduling and graph theory (decomposition of the complete graph Kn into perfect matchings).
- How are odd numbers handled?
- When N is odd, a perfect matching is impossible — someone has to sit out each round. The tool adds a phantom '(Bye)' slot to make the count even, then runs the standard circle method. Across N rounds, every real participant gets exactly one bye. The bye rotates fairly — no one sits out twice while another sits out zero times.
- How is this different from your Group Maker / Secret Santa tools?
- Group Maker splits N people into K disjoint groups in one shot — useful for breakout sessions or team picks. Secret Santa builds a single cyclic gift-giving assignment (A→B→C→A). The round-robin scheduler builds the entire matchup graph over time — N-1 rounds, each round a perfect matching, covering all C(N,2) unordered pairs exactly once. It's the right tool whenever you want a rotation, not a one-shot assignment.
- Can I reproduce a specific schedule later?
- Yes. The randomized order is seeded — the seed is stored in the URL-shareable state, and re-loading the tool reproduces the same layout. If you want fully deterministic output, switch to alphabetical order; same input always yields the same schedule.
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