Lumber Calculator

1. Enter the number of boards. This is the quantity of individual boards in your order or project. If you are calculating for a framing job, count all studs, plates, and headers separately.
2. Use actual dimensions, not nominal. A 2×4 is actually 1.5 inches thick and 3.5 inches wide. A 1×6 board is actually 0.75 inches thick and 5.5 inches wide. Using nominal sizes overstates the board feet and gives an inflated cost. The reference table below shows common actual dimensions.
3. Enter board length in feet. This is the purchased length, usually 8, 10, 12, or 16 ft. Use the actual sold length, not a cut-to-size measurement.
4. Enter price per board foot. This is optional but gives you a total material cost. Lumber yards and hardwood dealers price wood by the board foot. Big-box stores typically price by the linear foot or per piece, so convert if needed: divide the per-piece price by the board feet per piece.

Example: 20 boards of 2×6 lumber, each 10 ft long. Actual dimensions are 1.5 inches × 5.5 inches. Board feet per board: (1.5 × 5.5 × 10) ÷ 12 = 6.875 BF. Total for 20 boards: 137.5 BF. At $2.50 per BF, cost is $343.75.

A board foot is a unit of lumber volume equal to 1 inch thick, 12 inches wide, and 12 inches long (144 cubic inches). It is the standard unit for pricing hardwood and for estimating large framing projects.

Where T = thickness in inches, W = width in inches, L = length in feet. Always use actual dimensions, not the nominal (labeled) size. Nominal sizes like "2×4" or "1×6" are holdovers from when lumber was sold rough-cut at those dimensions. After drying and surfacing, material is removed, leaving the smaller actual dimensions found in modern dimensional lumber.