H-5. WHAT'S A "BOARD FOOT"?
Board feet can also be expressed as: BF, MBF (1000 BF), FBM (foot board measure), or
MFBM (1000 foot board measure).
Nominal is a description of size based on the lumber dimension in its rough sawn, green,
unseasoned condition. Unless otherwise specified, the board footage is based on lumber's
Lumber or timbers are often surfaced (also called dressed, or planed) down from nominal
dimensions to a net dimension. Further, the selling price of a 2" x 8" x 12' pine plank,
surfaced four sides (S4S) to 11/2" x 71/4" x 11'4" would still be based on its nominal
dimensions of 16 board feet, not on the actual net dimensions of 10.27 board feet. If the
lumber is sold in its rough sawn condition, the nominal and the net dimensions would be the
The standard net dimension of surfaced 1" softwood board is 3/4", whereas 2" and thicker is
surfaced to 1/2" under nominal dimensions. The net width dimensions get a bit trickier to
describe. Normally, in boards and construction lumber, the net dimension is 1/2" under
nominal width for material 6" or less wide, and 3/4" under nominal width for material 8" or
wider. The net dimensions of surfaced timbers are normally 1/2" under nominal dimensions
but can be specified to any net dimension.