In purchasing chickens over the last couple months, I've had the chance to see many people's set ups. I've seen everything from what amounts to mansions for very few chickens, to lean-to's offering a little shade for 30 chickens. Personally, though they say not to consider whether they free range or not, unless they spend every or almost every day in the coop/run, and instead get out and free range all day, you can keep a few more than what is considered optimum. I have a 4x8 at 5 feet tall at peak coop, with a 10x10x6 run. Conventional wisdom puts me at 8 chickens on the low end, and 16 at the high end. I'll probably end up somewhere in between. The extra few chickens body heat will keep them warmer while roosting on cold nights, and on the few days where it's required, the covered run is big enough for them to have room to move around comfortably.