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Calculation details
Planning estimate only. Verify dimensions, waste, coverage, product specifications, and local requirements before purchasing materials.
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What does this calculator estimate?
Board foot calculator: convert lumber dimensions into board feet and total cost, multiple boards at once. Editable prices, free, runs in your browser.
How this calculator works
Formula
Board feet = thickness (in) x width (in) x length (ft) / 12, per piece, times quantity.
Worked example
Ten pieces of 2 x 6 lumber, 8 ft long: 8 board feet each, 80 board feet total.
Frequently asked questions
What is a board foot calculator?
A board foot calculator is a tool that measures lumber volume in board feet by multiplying thickness, width, and length of a board. Our board foot calculator works entirely in your browser, no signup required.
Do I need to create an account or install anything?
No. Our board foot calculator is free, no-signup, and runs directly in your browser with no downloads or installations needed.
How accurate is the board foot calculator?
The board foot calculator uses the standard formula: (thickness in inches × width in inches × length in feet) ÷ 12. Results are precise as long as you enter accurate measurements.
Cite this tool
BoringToolsKit. “Board Foot Calculator.” boringtoolskit.com/board-foot-calculator/. Free to reference in articles, syllabi, and answer posts with a link.
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Where the divide-by-12 comes from
One board foot is 144 cubic inches: one square foot of area, one inch thick. A board 1 inch thick, 8 inches wide and 8 feet long runs 96 inches, so its volume is 1 x 8 x 96 = 768 cubic inches, and 768 / 144 = 5.33 board feet. The formula skips that conversion. Cubic inches need feet times 12, board feet need division by 144, and 12 / 144 reduces to 1/12. The divide-by-12 is that unit reduction.
Worked example: thickness 1, width 8, length 8, quantity 12. Per piece, 1 x 8 x 8 = 64, then 64 / 12 = 5.333..., shown as 5.33. The total multiplies the unrounded figure, 5.333... x 12 = 64 exactly, shown as 64. The displayed numbers do not multiply back: 5.33 x 12 = 63.96, short by 0.04. At quantity 120 the per-piece line still reads 5.33 and the total reads 640, a 0.4 gap on the round trip.
Boundary inputs and where the number stops meaning anything
Blank fields read as zero, so empty thickness, width, length and quantity print 0 bd ft per piece and 0 total instead of an error. Letters are worse: Number('abc') is NaN, so text in thickness prints NaN bd ft on both lines. Negatives pass through unclamped: thickness -2, width 8, length 8 gives -10.67 per piece, and quantity 4 gives -42.67.
The 2-decimal cap adds drift. Thickness 1, width 5, length 5 gives 25 / 12 = 2.0833..., shown as 2.08, and at quantity 6 the total reads 12.5 while 2.08 x 6 = 12.48. The larger real-world gap is nominal versus actual size: a surfaced 1x8 measures 0.75 x 7.25 inches, so 0.75 x 7.25 x 8 / 12 = 3.63 bd ft where the nominal entry gives 5.33. Ten boards total 36.25 instead of 53.33, about 32% less, so say which dimensions you measured.