The National Building Code adopted by most States provides well though-out 'minimum number of toilet facility' recommendations. As adopted by most States, the code, for example, requires a restaurant to have at least one men's and one women's toilet for up to 75 people. On the other hand a for a night-club the maximum is ,reasonable, reduced to 40 people. There are implementation of the code, however. that can results in people queuing to use the restrooms
(1) Outside seating distorts this formula. For the most part these people are not occupying the building but they can be expected to use the restroom as often as those within.
(2) The formulas are based on a standard restroom configuration that allow more then a single person at a time in the room. When the door to the restroom can be locked this reduces how many people can use the restroom at a given time. (See 'Occupant Locked Restrooms' below)
(3) There typically is no consequence when a restroom is closed for cleaning or for repair.
(4) When an occupant of a building is not allowed to use a restroom, redress is difficult.