Board Foot Calculator
Calculate board feet of lumber from thickness, width, length and quantity — and the total cost per board foot.
How it works
board feet = thickness(in) × width(in) × length(ft) × quantity ÷ 12
A board foot is the volume of a piece one inch thick, one foot wide and one foot long — 144 cubic inches. Because length is in feet while thickness and width are in inches, the formula divides by 12. Hardwood lumber is priced by the board foot, so this is how a lumberyard turns a stack of rough boards into a bill.
Worked example
One 1 in × 6 in × 8 ft board: 1 × 6 × 8 ÷ 12 = 4 board feet. At $6 per board foot that single board costs $24.
Frequently asked questions
Nominal or actual thickness — which do I use?
For pricing, use nominal (a “1-inch” board counts as 1 in even though it planes to 3/4 in); hardwood sold rough often is a full inch or more. When in doubt, measure the rough board, since that is what you are charged for.
How is board foot different from linear foot?
A linear foot ignores thickness and width — it is just length. A board foot is a volume, so two boards the same length but different sizes have the same linear footage but very different board footage and price.
How much waste should I add for a project?
Buy 15–20% extra hardwood beyond your net board feet. Rough lumber has splits, knots and wane you cut around, and defect-free yield is rarely more than 80–85% of what you carry home.
Related calculators
Estimates only — add for waste and confirm against local building codes and supplier specs.