The sum
Registrations needed = seats ÷ show rate, rounded up. If 60% of registrants come and you have 60 seats, you need 60 ÷ 0.6 = 100 registrations. Round up, not to the nearest: 200 seats at 60% is 333.3, and 333 registrations at 60% leaves you a seat short.
| Seats to fill | If 70% come | If 60% come | If 50% come | If 40% come |
|---|---|---|---|---|
| 30 | 43 | 50 | 60 | 75 |
| 60 | 86 | 100 | 120 | 150 |
| 100 | 143 | 167 | 200 | 250 |
| 200 | 286 | 334 | 400 | 500 |
What show rate to expect
For free in-person events, organizers interviewed by Eventbrite plan for 25 to 30% to drop out on the day, some up to 50%, and bad weather can push it higher. Online sessions run lower: published webinar attendance rates of 40 to 58% are collected in our webinar attendance benchmarks.
Your own past rate beats any benchmark. After two or three events, use the share who actually came, for that kind of event, on that day of the week.
Over-registering safely
Aiming above capacity only works if you can cope when more people come than usual. Before you open extra places:
- Know your hard limit. A fire limit isn't a target. If the venue has one, don't register past what you could seat if everyone came, unless you control the door.
- Keep a waitlist for anyone past your target, and move people up as others cancel.
- Make cancelling easy, so the people who can't come tell you, and their places go to the waitlist.
- Count at the door. Check-in tells you your real show rate for next time.
The calculator also shows the risk: how many people you'd have if your show rate turns out ten points higher or lower than you planned.
Moving the rate, not just the target
The other way to fill seats is to get more of your registrants there. Calendar entries, reminders with something new in them, easy cancelling and a real waitlist all help; the no-shows guide goes through each.
In Programmable Talk
Talk counts registrations against the capacity you set, and when it's full, people join a waitlist and move up in order as places free. Registrants can cancel with one tap on their page or by replying "cancel" to any email. Attendance comes back from check-in at the door or from Luma, Zoom and Eventbrite, so your next target uses your own show rate.