most venues should have an official figure. because to open they should get told a capacity based on the floor space and fire exits but the rule for it is stupid. take enw years for example, they got told they could only let in like 12,000 people. but that left heaps of room cause everyone was all close to teh stage and people would have cause riots if they couldnt get in, knownig there was all that space. so they let in about 25000 in the end.