posibly a ten by ten or maybe eight by eight i only have 6 chickens and 3 ducks but i used to have more until they were attacked so now i keep a 12 by 12 so i can get more + you want a large enough coop so they are not cramped together and start hurting eachother also are you going to have a run?
Well, don't laugh, but my son's trampoline takes up most of my backyard, and since these are "his" chicks I told him I was building a run UNDER his trampoline! and just connect the coop somewhere on the side of the yard. So a 10X10 should do huh? Thanks alot!
use a chichen tractor that can move aroun the yard that is what I use in the suburbs for my 12 hens with a big movable fence atached. It is great and does not smell but there is poop everywhere doesnt bother me LOL.