Board Foot Guide: Lumber Dimensions, Quantity, Waste, and Cost

Use the free Board Foot Calculator to turn your measurements and local prices into a project estimate.

A board foot is a volume measure used to price solid lumber. One board foot equals a board 1 inch thick, 12 inches wide, and 1 foot long. It does not describe the final shape of the project or the number of usable parts.

Use the standard formula

Multiply thickness in inches by width in inches by length in feet, then divide by 12. Multiply by the number of identical boards. Keep units consistent; using length in inches requires dividing the full cubic-inch result by 144.

Confirm the dimensions used for pricing

Construction lumber is commonly identified by nominal dimensions, while its actual dressed size is smaller. Hardwood may be sold rough or surfaced and thickness may be described in quarters, such as 4/4 or 8/4. Ask whether the seller calculates from rough, nominal, or actual dimensions.

Build a cut list

List every finished part with length, width, thickness, and quantity. Group similar parts and consider how they fit on available boards. Grain direction, color matching, defects, and joinery may prevent you from using every square inch.

Add waste deliberately

A simple project using clear, straight stock may need less waste than one requiring wide matched panels, long uninterrupted parts, or removal of knots and checks. Rough lumber also loses material during jointing and planing.

Estimate cost

Multiply purchase board feet by the seller’s price per board foot. Add milling fees, minimum charges, delivery, tax, and specialty services. Sheet goods such as plywood are normally priced by sheet rather than board foot.

Use the estimate as a planning range

Measure twice, use exact product dimensions or package coverage, and compare the result with supplier or contractor information. Taxes, delivery minimums, labor, tools, site conditions, and local requirements can change the final cost.

Worked board-foot example

A rough board measuring 1.5 inches thick, 8 inches wide, and 10 feet long contains 10 board feet: 1.5 × 8 × 10 ÷ 12 = 10. Six boards at those dimensions total 60 board feet. Adding a 15% allowance for defects, grain selection, and milling raises the purchase target to 69 board feet.

If the lumber costs $8.50 per board foot, the material estimate is $586.50 before tax, delivery, and milling charges. The seller may calculate from rough dimensions even when the surfaced board delivered to the shop is thinner or narrower, so confirm the pricing dimensions before comparing suppliers.

Build the estimate from a cut list

• List the finished length, width, thickness, and quantity of every part.
• Add machining allowance for jointing, planing, squaring, and trimming.
• Account for sapwood, knots, checks, color matching, and grain direction.
• Check available board widths and lengths before assuming every part nests perfectly.
• Separate sheet goods, molding, hardware, finish, and labor from solid-lumber board feet.

Common pricing differences

Hardwood dealers may use quarter-thickness names such as 4/4 and 8/4, sell random-width and random-length stock, and apply minimum board-foot rules. Construction lumber is usually sold by the piece using nominal dimensions. A board-foot calculation is useful for comparing volume, but it does not convert those selling methods into identical products.

Review notes

This guide was reviewed on September 21, 2026. The formula is thickness in inches × width in inches × length in feet ÷ 12. Read how our calculators work for our approach to units, rounding, waste, and prices.

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