Rule of thumb is 4 sq ft per bird inside. I have abt 6 sq ft/bird in mine, and no fighting. For outside, I did 80 sq ft/bird. I have abt 2000 sq ft for 24 hens. If I had it to do again, I would have built mine bigger than that. Much easier that way to keep live greens aplenty in the pen. As is, I expect to have to cross-fence and keep a place where new fresh grass is growing to keep them in grass year-round if possible. I really hate the idea of free range due to predators. Odds will catch up to you eventually if you do free-range enough. So if possible to build run big enough to replicate free-range somewhat, then that is safest. I never have fed mine store-bought feed only. They have had live greens and veggies and fruits from day one.
I used 6 ft welded wire 2x4 fencing set in cement at bottom for entire perimeter. I used 6" creosote poles for corner posts, set in cement. I put 6 ft steel T posts every 10 ft between corner poles, at 5 ft ht. I added 24" tall chicken wire around interior of pen to keep chooks from sticking their heads thru to prevent a coon from decapitating them. I installed a 5-mile fence charger 4KV. I put up 4 courses of hot wire (beginning at 8" ending at 42") and used a large stretch spring in each course midway to tension them and prevent them from becoming saggy. I ran the hot wire across the gate too using the same galv 14 ga wire wrapping it around a dowel about 4 times to form a coil to make a hinge/flex point for each of the hot wires to move freely when gate operated so wires will not fatigue and break. Be sure to bond fence to ground side of charger unit as well as to a 6 ft copper ground rod. Then be sure to bond gate fencing if any, to fence using the same wire coiled to form a coil hinge type thing, like the gate wires. It will move too when gate operates. I ran power 20 amp line and 3/4" water line to hydrant near coop too. I did no aerial protection yet. Lots of resident crows here and good luck so far. Deer netting is good and aviary netting too. Latter comes in 24 ft width and is common to protect corn and strawberries. You can also try stretching poly twine criss-cross over run to discourage hawks from snatch and grab operation. Hang shiny stuff from it like CD discs, pie tins, etc.
Power is in coop (8X16 for 24 hens) and two outlets for whatever plus two outlets at gate for charger and whatever. I hung 2 shop lights, 48" fluorescent twins. Linoleum over 3/4" osb flooors over 2x6 floor hoists on 6 creosote legs in cement . I ran linoleum up walls 16" between each stud and caulked it along top and sides where it is stapled. It slopes outward so that it covers the wall base plate 2x4. Will be for prevention of poop/bacteria build up on wall base plate, and also for easy hosing out when changing litter out twice a year. I put two guillotine type drop-down pop doors in my coop. They are 1/2" osb and are down all night every night. They op via small steel cable/wore rope and pulley systems with leads dropping down thru tiny holes in soffit beside center main entrance door. Loop in end of each goes around a roofing nail set in door casing on each side to secure the pop doors up/open all day. Simply unhook and let both drop down at night. Two lengths of plastic pvc guttering for feed and water troughs set on shelves to be removable and 8" at top from floor. Works great and no spillage of feed or water, ever. Water outside too, but no feed ever. (will attract crows, squirrels, blackbirds)Only daily garden waste/table scrap veggie/fruit treats.
