The board foot is lumber's native volume unit — one square foot of wood, one inch thick — and the only fair way to price boards that vary in every dimension. The formula is thickness × width × length ÷ 12, with thickness and width in inches, length in feet.
Worked examples
A 2×4×8: 2 × 4 × 8 ÷ 12 = 5.33 board feet; ten of them, 53.3. A 4/4 oak board 6″ wide and 10′ long: 1 × 6 × 10 ÷ 12 = 5 bd ft — at $6/bd ft, $30 of oak. The per-piece line keeps the arithmetic auditable at the lumberyard counter.
The nominal-size trap
Here's the catch every first-time buyer hits: a "2×4" actually measures 1.5 × 3.5 inches. Rough-sawn boards shrink in drying and lose more to planing; the nominal name survives from the rough size. Board-foot pricing uses nominal dimensions by convention — you pay for the tree's wood, including what became shavings. Hardwood thicknesses go by quarters: 4/4 is 1″ nominal, 8/4 is 2″.
Buying strategy
Construction lumber sells per piece; hardwood sells per board foot because every board differs. For project buying, take your cut list, compute board feet, then add 15–30% — defects, grain matching and jointing all eat stock. Fine-furniture makers buy the high end of that range without regret.
Adjacent estimates
Sheet goods (plywood, MDF) price per sheet — area math from the square footage calculator serves there. Structures need the stair and roof pitch calculators, and generic volumes convert in the volume calculator.
Nominal-dimension convention; retail hardwood pricing varies by grade.