DATUM

Board Feet Calculator — nominal vs actual

Board feet, linear feet and cost for framing lumber, showing both the nominal size you are billed for and the actual surfaced size you build with.

Board Feet Calculator — nominal vs actual

Board feet are billed on the nominal size, but you build with the actual size. A 2×4 is 1-1/2" × 3-1/2". This shows both, because mixing them up is how orders come out wrong.

nominal — what you pay for actual
Board feet are billed on the dashed outline. You build with the solid one. Size openings and spacing off the actual dimension, never the name on the invoice.
Nominal (what you are billed for)
Actual (what you build with)
Board feet, one piece
Board feet, total
With waste
Estimated cost
Linear feet

A board foot is 144 cubic inches of nominal lumber: nominal thickness (in) × nominal width (in) × length (ft) ÷ 12. Softwood is sold this way even though it is surfaced smaller — a nominal 2×4 finishes at 1-1/2" × 3-1/2", a 1× board at 3/4" thick, and nominal widths of 6" and over lose 3/4" rather than 1/2". Those surfaced sizes are the S4S dry dimensions in the American Softwood Lumber Standard; rough-sawn and green stock differ, so measure what the yard actually hands you before cutting a tight fit.