Board Feet and Lumber Cost Calculator
Calculates total lumber cost from board dimensions, quantity, price per board foot, and a waste factor. Use it when estimating material budgets for furniture, framing, or any woodworking project.
Last updated: September 2026
Formula below · 2 sources (fpl.fs.usda.gov, Wikipedia) · Updated Sep 2026
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About this calculator
A board foot is the standard North American unit of lumber volume equal to 144 cubic inches. With all three dimensions in inches, board_feet = (length × width × thickness) / 144; with length in feet it is (L_ft × W_in × T_in) / 12. The full cost formula used here is: total_cost = round(((length × width × thickness / 144) × quantity × wasteFactor × pricePerBoardFoot) × 100) / 100. The waste factor — typically 1.10 to 1.20 — increases the volume you buy to cover defects, trim ends and off-cuts. Multiplying by price per board foot converts volume to dollars, rounded to the cent.
How to use
You need 10 boards, each 96 inches long, 6 inches wide and 1 inch thick, at $4.50 per board foot with a 15% waste allowance (1.15). Board feet per board = (96 × 6 × 1) / 144 = 4 board feet. Total cost = 4 × 10 × 1.15 × $4.50 = $207.00. Without the waste factor the estimate would be $180.00, a $27 shortfall that could leave you short of material mid-project.
Frequently asked questions
How do I calculate board feet for lumber with different dimensions?
Board feet = (length in inches × width in inches × thickness in inches) / 144, or equivalently (length in feet × width in inches × thickness in inches) / 12. The formula works for any rectangular piece of wood. For example, a board 8 feet long, 4 inches wide, and 2 inches thick contains (8 × 4 × 2) / 12 = 5.33 board feet. When purchasing rough-sawn lumber, always use the nominal (rough) dimensions, not the finished planed dimensions, because lumber is sold and priced at nominal size.
What waste factor should I use for a furniture woodworking project?
A 10–15% waste factor (1.10–1.15) is appropriate for clear, premium hardwood where you are cutting mostly defect-free stock into large panels or long parts. For lower-grade lumber with knots, checks, and sapwood that must be cut around, 20–25% (1.20–1.25) is more realistic. Highly figured or quartersawn stock often commands a higher price and warrants careful layout to minimize waste, sometimes bringing the effective factor back down to 10%. Projects involving many short, narrow parts — like chair spindles or shaker pegs — can generate significant offcut waste even from high-grade stock, so 15–20% is a safe default for most furniture work.
Why is lumber sold by the board foot instead of by the linear foot or piece?
Board feet measure volumetric content, which directly reflects the amount of raw log resource consumed to produce the piece. Two boards of the same length but different widths or thicknesses represent very different amounts of timber, kiln energy, and milling labor, so selling by the linear foot or piece would create confusing price disparities. The board foot system allows a single price per unit to apply consistently across all dimensions, making it straightforward to quote, invoice, and compare prices from different suppliers. Softwood construction lumber (2×4s, 2×6s) is the main exception — it is sold by the linear foot or in standard lengths because dimensions are highly standardized.