How to assign attendees to in-person conference sessions by preference
This is for conference days in real rooms, not video breakout rooms. Have attendees rank the sessions in each time slot, give each room its seat count, place one slot at a time, and keep anyone from being placed in a session they already have. The example below runs a 3-slot day for 120 people.
By Sortround. Published 5 November 2026.
How do you place people in two or three rounds of sessions?
An organiser put this well on Microsoft's Excel forum in August 2024: an event with two rounds of workshops, people listing their top four, a limit of 25 per workshop per round, and each workshop on offer in both rounds so that 50 can take it in all, but not at the same time. Their spreadsheet solver reported no feasible solution, and they could not see how to let a workshop run in both rounds.
Rounds add two rules to the seat limits: a person is in one room per slot, and nobody should sit through the same session twice. Add a third rule, that everyone must get one of their listed choices, and there may be no answer at all if too many people list the same few. A "no feasible solution" message means the rules as written cannot all be met at once.
The manual method
- Plan the rooms first. List the slots across the top and the rooms down the side, and put the session you expect to fill in the biggest room. Run it twice if you can.
- Collect choices per slot. One form, with a first, second and third choice for each slot, closed a week before the day.
- Keep one sheet per slot. Work through the first slot as in the electives guide: count, draw, move people on.
- Check for repeats before the next slot. Anyone already placed in a session cannot have it again, so strike it from their choices on the next sheet and move them on.
- Print a list per room. Door volunteers need names by room and by slot, and people need their own day on a badge or a card.
This is honest work for a small meeting. It gets slow quickly as people and slots grow, because one move in an early slot changes what is left in every later one, so a late change means going back through the sheets.
Worked example: 120 people, 3 slots, 4 rooms
6 topics across the day, each running in 2 of the slots. Everyone ranks 3 sessions in each slot. A session with the same title in two slots is the same session, so nobody can be placed in it twice. The attendees are invented, and the counts are the output of the same solver the site runs.
| Slot | Hall, 50 seats | Room A, 30 seats | Room B, 30 seats | Room C, 20 seats |
|---|---|---|---|---|
| 1 | Grant writing: 50 placed | Leading a team: 30 placed | Data for beginners: 28 placed | Storytelling: 12 placed |
| 2 | Inclusive design: 50 placed | Grant writing: 20 placed | Evaluation basics: 30 placed | Data for beginners: 20 placed |
| 3 | Leading a team: 50 placed | Inclusive design: 30 placed | Storytelling: 20 placed | Evaluation basics: 20 placed |
| Slot | 1st | 2nd | 3rd | Unranked | No place | 1st already held |
|---|---|---|---|---|---|---|
| 1 | 116 | 4 | 0 | 0 | 0 | 0 |
| 2 | 66 | 34 | 20 | 0 | 0 | 54 |
| 3 | 38 | 50 | 22 | 10 | 0 | 82 |
Everyone has a place in every slot and nobody repeats a session. First choices fall from 116 to 66 to 38, and the last column says why: by slot 3, 82 of the 120 people had put first a session they already held from an earlier slot, so it was out of their choices. That is the no-repeat rule doing its job, not people being let down. 10 people in slot 3 could not have any of their 3: they already held one or two, and the rest were full.
What Solve does and does not promise here
Inside one slot, Solve gives the best possible result by its fixed order: the most people placed, then the most first choices, then second, and so on. The day as a whole has no such promise. Slots are solved in order, so slot 1 gets the pick of each room, and it is solved without looking at slot 3. Another plan might give slot 1 fewer first choices and slot 3 more, and Solve would not find it. On this example a new lottery number changed who went where and not the counts, but across slots that is not promised: who is placed early decides who is left later.
The strongest thing you control is the plan: the most wanted session in the biggest room, and in two slots if the speaker agrees.
Doing it on Sortround
- Set up an event with one round per slot, and add each slot's sessions with their room sizes. Give a repeated session the same title in both slots.
- In adult mode, share one link and let people join with their name, or add a list and print code slips.
- People rank each slot. Solve one slot at a time, in order, and read the fairness view after each.
- Publish. Each person sees only their own place in each slot. Print one roster per session for the door.
This example needs a paid plan twice over: more than one round, and more than 60 people. A paid plan holds 4 rounds, 60 sessions in a round and 2,000 people, and adds badges. Without paying, one slot for up to 60 people works in full.
Sortround places people. It does not sell tickets, run a schedule on the day or check anyone in, and video meeting tools have their own breakout rooms for online events.
Pages read for this guide, as they stood on 5 November 2026: Microsoft's Excel forum (August 2024).