Overbooking

Deliberately setting your registration cap above the room’s real capacity, because a predictable share of registrants will not turn up. You get the cap by dividing the room number by the share you expect to actually show, or by the working shorthand of 1.5 to 2 times the room for a free community event. The word sounds reckless and the practice is the opposite. Overbooking is what you do when you have written your no-show assumption down instead of hoping. Background casting on a film set works the same way: the 1st AD needs fifty bodies in frame, so casting books seventy. The risk on the other side is real too, which is why an overbooked event needs a waitlist and a door plan rather than just a bigger number.

Source: Not a single-author term. It is the planning implication the industry works from once you combine the published no-show ranges: free in-person events losing 40 to 60 percent of registrants (eventcloud) and DevOpsDays’ own 30 to 40 percent for free tickets (devopsdays.org/organizing). The 1.5 to 2 times figure is arithmetic on those ranges rather than a published study, so treat it as a starting multiplier you replace with your own measured attendance rate.

First used in: 2.2 · Registration ops: the no-show math.