Bantams or large fowl?
Will they be kept indoors at all times, have access to an enclosed run or kept free range?
What climate are you in?
Will you keep things such as feed, water and other items inside the coop which will take up available square footage?
Nesting boxes attached to exterior, drinker and feeder indoors I live in central indiana 1 we 1 rhode island red 1 welsummer 1 buff orphington and 7 barred rocks yes access to run about to a 40 sq ft run and I can expand the coop if I need to