Formula
Board feet = thickness inches × width inches × length feet × quantity ÷ 12. Planning board feet = board feet × (1 + waste percent ÷ 100). Optional material estimate = planning board feet × price per board foot.
Board Foot
Calculate board feet for lumber from thickness, width, length, quantity and waste allowance, with cubic-foot cross-checks, optional material cost and a printable lumber order worksheet.
Worked example
For 12 boards at 2 in thick, 6 in wide and 8 ft long: board feet = 2 × 6 × 8 × 12 ÷ 12 = 96 board feet. With 10% waste, planning board feet = 96 × 1.10 = 105.6 board feet. At 4.50 per board foot, the material estimate is 105.6 × 4.50 = 475.20.
Professional note
Master’s Tip: record whether the dimensions are nominal or actual dressed sizes. Board-foot arithmetic is clean, but a quote can drift if one person uses 2×6 nominal dimensions and another uses measured finished dimensions.
Regional and unit assumptions
Standard or basis: common North American board-foot volume arithmetic, where one board foot equals 144 cubic inches. Results are planning estimates, not structural grading, certified tally or legal trade measurement advice.
Assumptions and limitations
- Thickness and width are entered in inches; length is entered in feet.
- A board foot is a volume measure equal to a board 1 inch thick, 12 inches wide and 12 inches long.
- The calculator does not correct nominal lumber size to dressed actual size; use the convention your supplier, plan or worksheet uses and note it on the report.
- Waste allowance is a planning buffer only. It does not replace a real cutting list, grading check, moisture allowance, structural design or supplier tally.
- Optional cost is material arithmetic before tax, delivery, machining, fasteners, treatment, labour or currency conversion.
Methodology & Accuracy
How this calculator is checked
CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.
Formula used
Board feet = thickness inches × width inches × length feet × quantity ÷ 12. Planning board feet = board feet × (1 + waste percent ÷ 100). Optional material estimate = planning board feet × price per board foot.
Standard or basis
Standard or basis: common North American board-foot volume arithmetic, where one board foot equals 144 cubic inches. Results are planning estimates, not structural grading, certified tally or legal trade measurement advice.
Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.Master's Tip
Master’s Tip: record whether the dimensions are nominal or actual dressed sizes. Board-foot arithmetic is clean, but a quote can drift if one person uses 2×6 nominal dimensions and another uses measured finished dimensions.
Related calculators
Questions
How do you calculate board feet?
Multiply thickness in inches by width in inches by length in feet, multiply by the number of boards, then divide by 12.
What is one board foot?
One board foot is a volume equal to a board 1 inch thick, 12 inches wide and 1 foot long, or 144 cubic inches.
Should I use nominal or actual lumber dimensions?
Use the convention your supplier, plan or teacher asks for, and write it down. Nominal and actual dressed sizes can produce different board-foot totals.
Why add a waste allowance?
Waste allowance helps account for defects, knots, end trimming, machining loss, unusable offcuts and spare stock. Keep it separate from the measured board-foot total.
Does this create a cut list?
No. It gives a board-foot volume estimate. A final order should still be checked against real stock lengths, grades, cutting layout and supplier tally.
Calculation note
Board-foot estimating is a practical bridge between three-dimensional lumber volume and everyday trade purchasing. It turns thickness, width, length and count into one comparable quantity, but the dimension convention and waste assumption need to stay visible.
Board feet measure volume, not surface area
A board-foot total describes lumber volume. Two boards can cover different surface widths but still have comparable board-foot volume if their thickness, width and length multiply to the same cubic-inch amount.
Nominal and actual sizes must not be mixed silently
Lumber is often discussed by nominal sizes while finished boards may measure smaller after drying and dressing. A useful worksheet records which convention was used so a supplier quote, classroom answer or shop cut list can be checked later.
Waste belongs on a separate line
Defects, knots, saw kerfs, end trimming and machining can make the purchase quantity larger than the measured board-foot total. Showing the allowance separately keeps the arithmetic auditable.
The printable report is a quote note
A one-page board-foot record with dimensions, quantity, formula, allowance, price and notes is useful for lumberyard calls, project files, classroom worksheets and shop approvals.