DIY Cost Tools
Board Foot Calculator
Calculate board feet for solid lumber, add a waste allowance, and estimate cost using board thickness and width in inches plus length in feet.
Measure: Use the dimensions used by the seller for pricing. Confirm whether thickness and width are rough, nominal, or actual before calculating.
How the estimate works: The calculator uses your measurements, unit conversions, waste allowance, and product coverage to create a planning quantity. Review the formula shown above, then read the matching guide below before ordering. See How Our Calculators Work for assumptions and limitations.
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How this calculator works
Board feet = thickness in inches × width in inches × length in feet × quantity ÷ 12. Purchase board feet adds the selected waste allowance.
Nominal and actual sizes differ
Dimensional construction lumber is often named by a nominal size that differs from its dressed dimensions. Hardwood and specialty lumber may be priced from rough dimensions or thickness expressed in quarters. Use the dimensions specified by the seller.
Plan for defects and milling
Waste can include end checks, knots, sapwood, twist, matching grain, joinery, and surfacing. A cut list and board-by-board selection are more accurate than applying one allowance to every project.
Read the complete board foot guide: lumber dimensions, quantity, waste, and cost.
Board-foot example
Board feet measure volume, not surface area. Ten boards that are 1 inch thick, 6 inches wide, and 8 feet long equal 40 board feet: 1 × 6 × 8 ÷ 12 = 4 board feet per piece, multiplied by 10 pieces. If the supplier prices lumber by the board foot, multiply the calculated volume by the current price and then add an allowance for defects, grain matching, and cutting.
Use the dimensions the seller uses
Hardwood is often sold from rough dimensions, while construction lumber is commonly named by nominal dimensions that differ from its finished size. Confirm whether the invoice uses rough thickness, surfaced thickness, or a minimum billing increment. Track each thickness and length group separately; averaging mixed boards can hide shortages. Sheet goods, decking sold by lineal foot, and packaged trim may need a different calculator.