I think there are extremely few hotels that have 7-person rooms. But you could pretty well tell by the number of sleeping spaces you can have in the room. E.g. - if you have a double, and you're allowed a rollaway cot, there's probably a fire code limit of 3. If you have two doubles, a fold-out double sofa bed, and a rollaway, that would probably be a room (most likely a suite) that would have a fire code limit of 7.