I have 30 hens in a 10x4 foot coop. Its cramped, but they all cuddle onto two or three roosts with 8 roosts to choose from, so I don't think they mind. I'll be doubling the size this spring so they have more room to spread out when it gets warm. I figure they are only in there to sleep from 6pm to 4am the rest of the time they're in the run (200 square feet). It is a hassle to clean, have to add leaves for deep litter once a week and totally clean it out once a month, but if your run is big enough and you don't mind more work, a smaller coop is fine at least for a while. Especially if you have to choose between small and secure or big and less-secure (bigger coops have a larger perimeter that you have to predator-proof and patrol to watch for tunneling or attempted break-ins)
