Session capacity is a scheduling problem, not a room problem

Rooms get blamed for overflow. The agenda causes it.

When two strong sessions run opposite each other, attendance does not split evenly — it concentrates on one and leaves the other half empty. The room that overflows and the room that empties are usually a matched pair, scheduled in the same slot.

Look at the pairs, not the sessions

Before publishing, list every concurrent pair and ask which one a first-time attendee would pick. Where the answer is obvious, you have found your overflow.

Use registration signal early

If sessions accept interest at registration, the shape of the problem shows up weeks before the event, while the agenda can still change. Moving one session to a different slot is cheaper than moving two hundred people on the day.

Give the overflow somewhere to go

Where a clash cannot be resolved, plan the overflow rather than discovering it: a repeat slot later in the day, or a livestream in an adjacent room, both of which need to be decided while the schedule is still a draft.