I have a roughly 5 x 3 box I was planning on being my brooder box. I plan to have 10 meat birds and 5-8 other egg layers. Would my box be big enough or do I need to get a second brooder?
Common space estimates:
1/2 square foot of space per chick for the first two weeks
1 square foot of space per chick until age 4 weeks
2 square feet of space per chick until age 8 weeks
4 square feet of space per chicken after that (even as adults)
So if your box is 5x3 feet, that's 15 square feet, which is enough for:
30 chicks (first two weeks)
15 chicks (up to 4 weeks)
7 chicks (up to 8 weeks)
3 adult chickens
(Actually, it will hold a few less after you subtract the space taken up by the food and water, but that's at least close.)
If you want 15 to 18 birds, you could brood them all in that box for the first two weeks, but it will be a bit too small by 4 weeks.
You might want to separate the meat birds and the layers after the first few weeks, so that would be a good time to add a second box.