Box Dimensions

I read a few different help sites on how to figure your box dimensions but it was over my head. Math has never been my strong point:uhoh: :shakehead . Figured there's someone here who can figure this out easily. Was hoping you could tell me what size pieces of wood I'll need (front,sides,top,and bottom).
Need to make two sealed boxes
One for a 12 inch sub 1.15 cubic feet
One for a 15 inch sub 2.18 cubic feet
This would help me greatly :grinyes: I'm gonna attempt a custom box
but I need these figures first to go off of.