Board Foot Calculator. Enter your board's thickness (inches), width (inches), length (feet), and number of boards to calculate total board feet of lumber. The Board Foot Calculator returns both per-board footage and the cumulative total — handy when pricing hardwood by volume at the lumber yard. Also try the Programmable Calculator.
A board foot is a unit of lumber volume equal to a board that is 1 foot long, 1 foot wide, and 1 inch thick — equivalent to 144 cubic inches or 1/12 of a cubic foot. Unlike linear feet (length only) or square feet (area only), board feet measure three-dimensional volume, making them the standard unit for buying and selling hardwood lumber. See also our use the BTU Calculator.
Use the formula: Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12. For example, a board that is 1.25 inches thick, 10 inches wide, and 8 feet long equals (1.25 × 10 × 8) ÷ 12 = 8.33 board feet. Multiply by quantity to get the total board footage for your project.
A standard 2×4 that is 8 feet long contains (2 × 4 × 8) ÷ 12 = 5.33 board feet. Note that a '2×4' refers to nominal dimensions — the actual surfaced size is 1.5 inches × 3.5 inches. Board foot calculations are typically done using nominal dimensions for rough or hardwood lumber.
A linear foot measures only the length of a board (one dimension), while a board foot measures volume (thickness × width × length). Linear feet are used for trim, molding, and materials sold by length alone. Board feet are used for hardwood lumber where thickness and width vary significantly between pieces.
Hardwood lumber thickness is expressed in quarters of an inch. '4/4' means 4 quarters = 1 inch, '6/4' means 1.5 inches, '8/4' means 2 inches, and so on. These are nominal or rough-sawn dimensions — the actual surfaced thickness will be slightly less. Always use the nominal thickness when calculating board feet.
Log board footage uses specialized scaling rules. The most common is the Doyle scale: Board Feet = ((Diameter − 4) / 4)² × Length. For a log with a 10-inch small-end diameter and 17-foot length, that's ((10 − 4) / 4)² × 17 = 2.25 × 17 = 38.25 board feet. The Scribner and International scales give slightly different results.
Hardwood boards come in random widths and thicknesses, so pricing by linear foot would be inconsistent — a narrow thin board would cost the same as a wide thick one of the same length. Board feet account for all three dimensions, creating a fair, volume-based pricing standard across different board sizes.
The weight depends on the species and moisture content. Red oak weighs roughly 3.9 to 4.2 pounds per board foot when air-dried (approximately 12% moisture content). White oak is similar at around 4.0 to 4.4 pounds per board foot. Knowing board footage helps you estimate total weight for shipping or structural load planning. You might also find our Square Footage Calculator useful.