Also calledAttritionAttendance rateShow-up rate
What is normal
Paid events see roughly ten to twenty per cent. Free events routinely see forty to fifty, and free virtual events more. The price paid is by far the strongest predictor: anything that costs nothing is easy to skip.
The levers that work
A price, even a small one. A reminder sequence in the last week with the badge attached. Something scheduled that is personally theirs — a meeting, a session seat, a hosted appointment. And making the badge easy to find on a phone at the door, because a visitor who cannot find their QR sometimes does not come in at all.
Report it honestly to exhibitors
Exhibitors who discover the difference between registrations and attendance on their own stop trusting every other number you give them. Publishing verified attendance, and the no-show rate alongside it, is worth more over three editions than a flattering headline figure.