The reason I asked where you live is that climate makes a difference in how big your coop needs to be. In western SD, at over a mile elevation, I cannot keep chickens in a coop with only 4 sq ft per bird, because they may be "cooped up" for weeks at a time. Many chickens refuse to go out into the snow. Sometimes the storms are very bad. I try to have 10 sq ft per bird of inside space.
However if you live in a very warm climate, your birds may only sleep in the coop. In that case you may not need the oft-cited 4 sq ft per bird. (You will, however, need excellent ventilation and protection from drafts across the sleeping area (the roosts), no matter where you live.)
However if you live in a very warm climate, your birds may only sleep in the coop. In that case you may not need the oft-cited 4 sq ft per bird. (You will, however, need excellent ventilation and protection from drafts across the sleeping area (the roosts), no matter where you live.)