I've been working on the coop for most of the day. I came in for a lunch break and to look up the dimensions of an average nest box, which seems to be about 12" length X 12" width X 9" high. In the picture, you can see the girls inspecting my handiwork. Just call me Handy Mandy. I may not know what the heck I am doing, but it's been fun trying to figure it out.