umm 12x12 is 144 square feet /25 birds is almost 6 sqft per.From personal experience with trying to put birds in 1sqft per bird ratio.. for meat. your going to hate the smell and mess. Its hard to keep clean. your going for 2 per sqft. I recommend at least 3 sqft per bird if you can. This is personal preference. I have since graduated to a 300 sqft pen for meat birds. I use a dirt floor and it makes cleaning easier. Meat birds in my opinion are nasty little poop factories that taste really really good!