You will get a variety of answers to any question - my opinion is watch your chickens and trust your instincts - you'll know when they're not happy. But do a bunch of research as to proper square footage - you don't want there to be too little that will cause them to bicker and set in bad habits early on that they probably won't outgrow. If you don't want to purchase any books, go to the library and do some research. I got most of my knowledge from an old English book I've listed on my BYC page. I think the main footage issue in the coop is plenty of room on the roost. With that being said, they all seem to want to squat on the one that's the smallest and closest to the door - go figure. I also think more square footage is important outside, where they spend most of their waking hours. Since I can't let them free range unsupervised anymore due to bobcats and owl losses, I've added an additional enclosed "play area" using wire gating next to their enclosed run that I open up at least 4 days a week or more as a "treat". Mine now have well over 30-40 s.f. outside per hen, but only about 12-15 in their permanent run. I'm planning on adding more permanent and separate play areas next year that I can seed and grow grass on to rotate them through over the season - they do love to tear up grass! Good luck!
Gail
Gail