Seriously speaking & thinking out loud; Your calculations might be correct, but I find my chickens like their own personal space & someone else's too!
You won't be packing them in like sardines, they need & thrive in spacious living quarters. OK, mine are a small bunch of spoiled chicken-brats. currently 2 hens,(1 1/2 & 2yrs old), 1 rooster,2 1/2 -3years old, + 3 biddies approx 1 month old, give or take a week. All sleeping in my outdoor coop,4'highx4' wide,x12' long. My coop is crafted from salvaged pallets. We ain't fancy, I just love my chickenz!