TradesHow this works
A board foot is a volume of lumber: nominal thickness times width in inches, times length in feet, over twelve. It uses the nominal size, so a 2 by 8 is board-footed as a full 2 by 8 even though the surfaced board is smaller. That smaller dressed size is shown for layout, but it does not change the board feet.
Once you have the board feet, the buying question is which way to pay. Lumber gets quoted both by the board foot and by the piece, and the cheaper one is not always the one it looks like. Enter both prices and the tool converts the per-piece price into dollars per board foot, compares them on your quantity, and tells you which to buy.
Common questions
How do you calculate board feet?
A board foot is the nominal thickness in inches times the nominal width in inches times the length in feet, divided by twelve. A 2 by 8 that is 10 feet long is 2 times 8 times 10 over 12, which is 13.33 board feet. Note it uses the nominal size, so a 2 by 8 counts as a full 2 by 8 even though the dressed board is 1.5 by 7.25 inches.
Why does board foot use nominal, not actual, size?
Board feet are a pricing and ordering unit that predates surfacing, so the trade settled on the rough nominal size before the board is planed down. That is why a 2 by 4 is board-footed as a full 2 by 4. The dressed size still matters for fit and layout, so the tool shows it, but the board-foot math uses nominal.
Should I buy by the board foot or by the piece?
Whichever is cheaper for your board, and it is not always obvious. Convert the per-piece price to dollars per board foot by dividing it by the board feet in that piece, then compare it to the board-foot rate. Hardwood is usually sold by the board foot and dimensional softwood by the piece, but yards vary, so the tool does the conversion and tells you which wins.
Sources: Board-foot formula (evergreen): thickness x width x length / 12 · Nominal vs dressed sizes: American Softwood Lumber Standard (DOC PS 20) · All prices are user inputs (evergreen, no stored figures). Engine version 1.0.0. Risk tier 1.