Sorry, I left a bit out of crucial info.
The Rule of Thumb for interior space for chickens is 4 sq ft/ bird. In the intensive commercial management schemes, it can drop as low as 1-2 sq ft/bird. You dont wanna go there and I wont belabor it.
Birds need enough room inside to roost, eat and nest and thats about it - once the sun is up and laying is over (noon-ish) they need to get their feathered butts outside.
Outside it varies and there are many, many possibilities. For range management, the old standard was 500/ acre = 87 sq ft.
M. Jull says 300/acre = 145.5 sq ft.
There is always some newfangled 'yard management' scheme making the rounds, but most people dont really grasp range management on the whole. They just figure anything outside is good, no matter how much (or how little) space is given. Some even think that any outside time, by itself, constitutes "free ranging."
Regardless, most dont even come close to that sort of space allowance, by a long shot.
I give these space allowances outside, but recognize that not everyone may be able to. If that is the case, FEWER birds are always better than more when space is tight and no matter what you do, you dont want them on bare dirt/mud. When space is tight, this means a litter of some kind is needed, which is second choice. Straw is good, shredded mulch maybe better. Live grass is best.
I hope this helps.