Starting off the peeps will need 1/2 square foot per bird. You have 16 square feet in your brooder, so 32 to start, however by the time they are 4 weeks old they need 3/4 square foot per bird, and by 8 weeks they will need 1 square ft per bird. I would think 15 chicks would work well. Most folks crowd more than I would. I'm sure others have a opinion. This is what I recommend for 16 square feet. Good Luck.
bigzio