The numbers
Every capacity on this site is worked out from the room’s real dimensions and the spacing that layout actually needs, rather than from a single number.
How
These are whole-room figures, not furniture footprints, and the difference is the thing most venues get wrong. A 1.8 m round of ten occupies about 0.9 m² a head as furniture — but a banqueting room needs about 1.6 m² a head once you include the chairs, getting out of them, and a route for the plates. Quoting the furniture number tells you a barn seats twice what it seats.
So: round tables 1.6 m² a head, long tables 1.4, ceremony rows 0.8, a standing reception 0.65. Then a tenth to a third of each room comes off first for the bar, the cake table, the band, and — outdoors — the beds, the paths and the trees.
And the licence
Where a room has a licensed maximum, that wins, even where the arithmetic says more would fit. A number on a website is not a capacity if the fire officer disagrees with it.
The figures here are deliberately conservative. We would rather you arrived and found the room roomier than you expected.