The standard measurement in the lumber industry is 1/4's. For instance, a 2" board is referred to as an 8/4. And the size refers to the size of the board rough, before it is planed and ready to sell, so a 2x4 actually starts out as a 2" x 4" but once it is planed on all 4 sides, it is only 1 3/4" x 3 3/4".