Oh..... I may not be the one to answer that. We have a brooder that's basically about a 5x5' Rubbermaid or similar storage shed, that they sleep in. It's inside maybe a 30 x 40' chain-link enclosure or "run" although honestly these birds really don't exercise. They are harvested so young we basically consider them chicks, I mean they ARE chicks. We use this arrangement for all our other chicks up to about the age of eight weeks or so, at which point we integrate them with the big girls, and it's perfectly adequate for 10 to 12 laying pullets up to that age. Our 9 CX seemed quite comfortable in it. I don't know what other folks would say about this or recommend, I'm just telling you what we do.Square feet, I think.