How long should a brainstorming session be?
Last reviewed by The thinkdrop facilitation team
A brainstorming session should last 45 to 60 minutes, with idea generation timeboxed to 15 to 20 minutes inside it. Remote sessions should be capped at 45 minutes because video attention drops sooner. Beyond an hour, idea quality falls and the group starts repeating itself, so run a second session rather than extending the first.
Key facts
- In-person session
- 60 minutes
- Remote session
- 45 minutes
- Idea generation
- 15–20 minutes, timeboxed
- Silent opening round
- 5 minutes
- Crazy 8s round
- 8 minutes
- Point of diminishing returns
- ~60 minutes
Step by step
- Budget 60 minutes in person — Five to frame, five silent, twenty building, fifteen grouping, ten deciding, five assigning. That split leaves enough room for the two phases teams usually skip: grouping and assigning.
- Budget 45 minutes remotely — Cut the building phase, not the deciding phase. Attention on video degrades faster, and a session that ends without owners was not worth the calendar slot.
- Timebox generation visibly — Put a timer where everyone can see it. Open-ended generation produces fewer ideas than a visible 20-minute limit, because the deadline is what stops people editing themselves.
- Split rather than extend — If the topic genuinely needs more, run two sessions a few days apart. The gap does real work — people arrive at the second one with ideas they had in the shower.
Where the time actually goes wrong
Most sessions overrun on generation and then run out of time for convergence, which is why so many end with a photo of a board and no decision. Protect the last 20 minutes: grouping, voting and assigning are what turn a session into work.
Asynchronous sessions run on a different clock
When the board is open for 24 to 48 hours, generation is effectively unlimited and cheap, and the only synchronous cost is a 20 to 30 minute call to group and decide. For distributed teams this is usually the better trade.
Frequently asked questions
How long should a brainstorming session be?
45 to 60 minutes, with idea generation timeboxed to 15 to 20 of them.
Can a brainstorming session be too long?
Yes — past about an hour, idea quality drops and the group starts restating what is already on the board.
How long should a remote brainstorm be?
45 minutes maximum on video, or asynchronous generation plus a short call to decide.
How much time should be left for choosing ideas?
At least the final 20 minutes, for grouping, voting and assigning owners.