Read an article that recomends 1-2 sq ft per chick till a month old in the brooder. I used about 4 inches of pine shavings in my brooder. I had an outside play area for them and would stir the shavings and do my maintaince(filling feed/water and cleaning) on the brooder while they were outside. My six had 8 sq ft of brooder. At one month they had outgrown it and moved to the coop/run.