My 12 year old son wears a size 12 jeans/pants but I recently bought him a size 12 pants (regular) so he needed a belt to hold him up to hold her. I ordered this medium sized Dockers Boys belt for him and it fits him well. It closes the belt with several holes (about 4), so the average size will easily fit a child who also wears (regular) size 12 pants. For a child wearing a size 10 and under I would advise going for a small one as a size 12 (slim) child will use a medium sized belt which is as