I have 4 hens in a 4x4 coop, and mine use it only for sleeping and laying. I started with 5in this coop for about a year until one of the hens passed. There was a lot of fussing and jostling about for months when there was 5 in there and one of the girls chose to go back to the small intro coop...
It depends. It varies depending on your climate, how much time they actually get outside the run, what breed and size of chickens you have, and what you really consider to be a good quality of life for your chickens. I will say, there is not a prefab coop I've ever seen that had an adequate run...