I should've specified better - floor space actually eaten up by nests does not count as usable floor space. Chicks can't even fit under mine since bedding keeps getting kicked under there so the space underneath is completely unusable.
4 sq ft in coop, 10 in run is the usual recommended minimum on here. Note that for some flocks that is plenty good enough, but for others, it won't nearly be enough and you'll end up needing to expand or getting rid of some birds to maintain the peace.
Nest boxes are not included in usable...