How it works
A board foot is a volume measurement — one square foot, one inch thick. Because thickness and width are conventionally measured in inches while length is measured in feet, the formula divides by 12 to bring everything onto the same footing.
board feet (per board) = (thickness × width × length) ÷ 12
total = board feet per board × quantity
Board feet is a U.S. lumber-trade unit with no natural metric equivalent, so this calculator stays in inches and feet regardless of the site's locale switch — the same way it works on an actual lumber yard's tally sheet.
Worked example
10 boards, each 1 in thick, 6 in wide, 8 ft long, at $4.00/bf.
- Per board: 1 × 6 × 8 ÷ 12 = 4 board feet.
- Total: 4 × 10 = 40 board feet.
- Cost: 40 × $4.00 = $160.00.
10 boards come to 40 board feet, costing about $160.00.
Common questions
Should I use nominal or actual lumber dimensions?
Board footage is conventionally priced on nominal dimensions — a "1×6" is sold and billed as 1 in × 6 in, even though the actual dressed size is closer to ¾ in × 5½ in after milling. Use the nominal size printed on the price tag unless your supplier explicitly quotes actual dimensions.
Is a board foot the same as a linear foot?
No — a linear foot only measures length and ignores thickness and width entirely, so it's only meaningful for a fixed, known cross-section (like trim or molding). A board foot is a true volume measurement, which is why it's the standard for pricing rough lumber of varying dimensions.
Why doesn't this calculator switch to metric?
Board feet is specifically a U.S. and Canadian lumber-trade convention — outside North America, timber is typically priced by the cubic metre or lineal metre instead, which isn't the same calculation. Rather than invent an artificial metric "board foot," this page stays in the unit lumber yards actually use.