My numbers are a bit deceptive and could actually be inaccurate, since I am not certain of the exact dimensions of my coop. I believe our coop is 8x10 but may actually be 10x12. For the purposes of this poll I am going to assume the smaller size. We have 25 chickens. 80 sq ft ÷ 25 chickens gives them 3.2 sq ft per bird, which is a bit less than the 4 sq feet recommended and which I myself often tout when newbies ask. (If it's 10x12, then my chickens have 4.8 sq ft per bird.) However, this actually works for us at the moment. We have an established older flock of 12 EE/BL/BO hens and a roo, plus this spring's flock of 10 BA and two cockerels - one BA and a BJG. All these birds are calm, docile, non-aggressive, and get along well together. In addition to this, our roosting arrangements are a bit unconventional. Along one side above the nests there is a regular roost. Along the opposite wall we have installed a long pallet, perhaps 6x4'. This provides all the birds more than enough room to roost without crowding.
The birds spend their day in a fenced run of about half an acre (guessing) which contains an abundance of grasses and forbs for foraging. I have not calculated the square footage per bird in this run, but it's considerable. At about 3:00 in the afternoon they are released to free-range on three or four acres until dusk. Again, I can't calculate the square footage per bird. But because they are essentially free all day, I don't feel they are suffering any by not having the recommended allowance of "four square feet per bird" in their coop at night. There is no evidence of bullying, feather pulling or pecking.