One of the unhappiest experiences the home furniture maker can run into
is buying a piece of wood and then finding it's just a little too short.
Because of shrinkage and varying standards of mill planing, there is a
difference between the actual "net" size of dressed lumber that you get
from the lumberyard and the nominal size that you order.
However, plywood is sold in the exact dimensions as offered.
Board lumber nominally 1 inch thick will actually measure from 3/4 to 7/8 inch
(usually 13/16 inch). And its actual width will be 3/8 inch less than its nominal
width, in pieces between 2 and 6 inches wide; in wider pieces the difference
will jump to 1/2 inch.
Similarly, dimensional lumber of 2-inch nominal thickness actually measures
15/8 inches. So be specific about the size you want, and check the extent
that the dressed lumber varies from the rough-cut size.