Ive read several times that you need at leasr 1 sq foot per chicken. Ours isnt very large and we have 5 chickens. We live in a cold climate and feel they need to cuddle in winter. LOL
It still needs doors and hardwarecloth etc. should be done in a week or two.
The size of your coop depends on a few things, such as your climate and how much time your birds will actually spend in there. (1 sq ft per chicken is factory farming conditions, not exactly conducive to good health. )
Another factor is the size of the run. Will you free range? Will they have a covered area outside the coop where they can hang out if it is raining or snowing or will they need to be inside?
One rule of thumb is 4 square feet inside the coop, 10 square feet in the run. But the more room you have, the better, especially if they will need to be inside for long periods of time.
Good luck with your flock!
I agree with most of this except 1 square foot per chicken was in most care books I read, but that is INSIDE coop requirements not to include the run. My run is roofed and secure from preditors so most of the year, in all weather, my chickens can come and go as they please. I will only close them in for a blizzard type condition...we live in Minnesota.
And that is why I said, "it depends".
Imagine if you had decided, like many people do, to have a secure coop inside a large area of open electronet fencing. Food and water stations are inside the coop, as are dustbathing areas, roost poles and nest boxes. In the winter the chickens will need to stay inside for days, maybe weeks at a time during winter storms or very heavy snow. If they only have an area that's only a little bigger than a sheet of notebook paper each, you'll have feather picking, harassing, injuries and probably deaths if you pack 48 chickens into a 6 x 8 coop. They won't even have room to stretch their wings.
Take that same 6 x 8 coop, attach it to a secure run with the food and water outside, with an area protected and accessible all year long with scratching and dustbathing areas, and a milder climate where they have time to be outside or free range every single day and all they do is sleep in the coop, and you can get many more chickens in that same coop space where they will stay healthier and happier. (Although I'd still only put around 15 in that scenario, myself.)
What works for meat birds that you slaughter at 8 weeks will be different than what works for layers that you replace every 2 years, and will be much different for backyard owners that want their chickens to live long, healthy, happy lives. There's also a bit of trial and error involved.
I have a few old hens that "rule the roost" They let everyone else know when they are in a bad mood, and won't let any one near them or even roost near them. It's funny to see two chickens on one end, then a 2-3 foot gap on the roost pole, then everyone else crowded on the other end. If they don't have a large amount of personal space, feathers will fly. Expecting them to be happy in 1 square foot of space, even just to sleep, is crazy. Chickens need room to establish their pecking order. Younger ones need space to stay away from the bullies, etc.
There are so many variables to consider when someone asks "Is this enough space?"