Board feet uses nominal softwood and rough hardwood size, not the finished size
Figure lumber on its named size — nominal for softwood (a 2×4 is figured 2×4, not 1½×3½; DOC PS 20) and rough quarter thickness for hardwood (4/4 = 1″; NHLA).
What this diagram shows
A comparison of how board feet is figured for softwood and hardwood. On the left, a 2 by 4 end-section: the dashed outline is the nominal 2 inch by 4 inch size and the solid wood inside is the actual surfaced 1½ inch by 3½ inch. Board feet is figured on the named 2 by 4, so a 2×4×8 is 5.33 board feet — the value you buy and pay for — not the 3.5 board feet you would get from the smaller surfaced size. On the right, the hardwood quarter system: rough thickness bars for 4/4 equal to 1 inch, 5/4 equal to 1¼ inch, 6/4 equal to 1½ inch, and 8/4 equal to 2 inches. Hardwood is sold rough by the quarter-inch; a 4/4 board is 1 inch rough and surfaces to about 13/16 inch, but board feet and price use the 1 inch rough size.
Board Foot Calculator
Free board foot calculator: build a lumber cut list and get total board feet, MBF, pieces and linear feet. Nominal sizes or custom hardwood, no signup.
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