Measure space for chickens in feet not acres. Comfortable living for a chicken is 8 square feet per bird and outside access during the day. 18 inches space per bird on the roost is good. Free range, 25 birds birds can happily live in a space no bigger than a regular city type lawn. A 20Ft X 30Ft coop is where my 25 birds roost by choice as they have larger accommodations elsewhere on the farm but prefer the smaller warmer space especially in winter.