Where each number comes from
The licensed capacity is worked out from occupancy density for the use class and checked against evacuation capacity: width of exits, number of routes and maximum travel distance to an exit. In assembly use with standing areas or areas with tables, the usual reference density is one person per square metre of public area. It is a safety number, not a service number.
The banqueting capacity is decided by the set-up. Once the tables are placed with their diameter, their chairs and the space those chairs take when people sit back, plus the service gangway between chair backs and the escape routes, the number left over is what you can serve. No formula replaces it: you have to place the tables.
Why the licence figure is almost never what you can serve
Because the licence counts people and a banquet counts tables with space around them. A 180 cm round with ten covers takes, with its chairs pulled out and its share of the service gangway, fifteen to eighteen square metres. That is 1.5 to 1.8 square metres per person, against the one square metre the licence usually counts.
That is where the ratio comes from: in a clean rectangular room, banqueting capacity runs at 60–65% of the licensed figure. It rises towards 75% in very regular rooms with no obstructions; it drops below 55% in rooms with columns, changes of level or access through the middle.
What service takes away
Before the first table goes down, there is floor area that is already gone. It is worth subtracting it explicitly rather than discovering it at the end.
- Service gangway: 60 to 90 cm clear between the chair backs of adjacent tables, with the chairs occupied.
- Escape routes: clear runs to the exits, straight and unobstructed, at the width the fire strategy requires.
- Office or service point: the tray area and the run from the kitchen, which in large rooms can take 15 or 20 m².
- Bar, buffet and dance floor: these are set-up, not decoration, and they take what they take. A sensible dance floor for 150 covers is around 25 m².
- Top table and the space in front of it: it needs at least 1.50 m clear for the couple, the photographer and service to pass.
How to document the capacity you offer
With the plan of that specific set-up and the number that comes out of it, kept together and dated. This is not paperwork for its own sake: it is what lets you answer in writing with confidence, and what covers you if a client later maintains they were told something else.
The wording that works in a quote has two parts: the maximum capacity of the set-up offered, and the sentence making clear that the number belongs to that set-up. Without the second part, any later change of format drags along a number that is no longer valid.
What happens in an inspection
An inspection checks the licensed capacity and the state of the escape routes: that exits are usable, signed and clear, and that the number of people does not exceed what is authorised. Having laid out below that number is not a problem; an escape route blocked by a table is, even with fewer people than authorised.
That is why the right order when laying out is to draw the escape routes first and place the tables around them afterwards. The other way round, the route ends up wherever there is room left, which is exactly where it should not be.