Well rule of thumb for a small flock is around 4 sq ft inside and 10 sq ft outside. In a 4x8 coop would hold 8 large fowl birds with a 10x10 run. There is not a magic number but the more the better. I have a 20x30 coop with 8x8 space for 40 chicks about 4 weeks old and the rest of the 20x30 for...