# Board Foot Calculator URL: https://speedycalculator.com/calculators/construction/board-feet/ Last updated: 2026-10-25 > The board foot calculator works out the board feet in lumber from thickness, width and length, for one piece or a whole stack, and prices the order from a cost per board foot. ## Inputs - Thickness (in, cm, mm, ft, m) — Use quarters for rough lumber: 4/4 = 1 in, 5/4 = 1.25 in, 8/4 = 2 in - Width (in, cm, mm, ft, m) - Length (ft, m, in, yd, cm) - Number of pieces - Waste allowance (%) - Price per board foot (/board ft, /m³, /ft³) ## Results - Board feet per piece - Total board feet - Board feet to buy (with waste) - Total linear feet - Estimated cost ## Formula ``` Board feet = thickness (in) × width (in) × length (ft) ÷ 12 Total = board feet per piece × pieces × (1 + waste) Cost = total board feet × price per board foot ``` ## Explanation Hardwood and many specialty lumber yards sell by the board foot, a volume unit equal to a board 1 inch thick, 12 inches wide and 12 inches long (144 in³). Knowing the board footage lets you compare prices between yards, check an invoice and plan how much rough stock to buy for a project. Use the nominal thickness for rough-sawn stock (a 4/4 board counts as 1 inch) and the actual size for anything else. ### How to use the Board Foot Calculator - **Thickness** — Use quarters for rough lumber: 4/4 = 1 in, 5/4 = 1.25 in, 8/4 = 2 in - **Width** - **Length** - **Number of pieces** - **Waste allowance** - **Price per board foot** - Every result field is editable: type into **Total board feet** or any other result and **Length** plus every other field update to match. Results update as you type, and every field accepts the units shown in its menu. ### How it works Multiply thickness and width in inches by the length in feet and divide by 12. Multiply by the number of pieces, add a waste allowance for defects and offcuts, then multiply by the price per board foot. ### Board feet in common sizes (per 8 ft length) Nominal sizeBoard feet per footBoard feet in 8 ft1×40.3332.671×60.541×80.6675.332×40.6675.332×6182×81.3310.72×101.6713.32×122164×41.3310.76×6324 ### Tips for an accurate estimate - Measure every dimension twice and write the unit next to each number – most estimating errors are unit mix-ups (inches entered as feet). - Pick the unit in each field's menu instead of converting by hand; the calculator converts everything to the same base before it multiplies. - Round up only at the very end. Rounding each dimension first can add several percent to the final quantity. - Suppliers sell in whole units – bags, boxes, sheets or quarter yards – so always round the final order up, not down. ### Common mistakes to avoid - Mixing square and cubic units: square feet measure area, cubic yards measure volume, and you need a depth to go from one to the other. - Using nominal lumber sizes where actual sizes matter (a 2×4 is really 1½ × 3½ in). - Forgetting that 1 yd³ = 27 ft³, not 9 ft³ (9 is for square yards). ### Inputs explained FieldWhat to enterThicknessUnits: in, cm, mm, ft, m. Use quarters for rough lumber: 4/4 = 1 in, 5/4 = 1.25 in, 8/4 = 2 inWidthUnits: in, cm, mm, ft, mLengthUnits: ft, m, in, yd, cmNumber of piecesA numberWaste allowanceIn %Price per board footUnits: /board ft, /m³, /ft³ ### What each result means - **Board feet per piece** = [Thickness]×[Width]×[Length] - **Total board feet** = [Thickness]×[Width]×[Length]×[Number of pieces] - **Board feet to buy (with waste)** = [Total board feet]×(1 + [Waste allowance]÷100) - **Total linear feet** = [Length]×[Number of pieces] - **Estimated cost** = [Board feet to buy (with waste)]×[Price per board foot] ## Worked example Inputs — Thickness: 1 in; Width: 6 in; Length: 8 ft; Number of pieces: 10; Waste allowance: 15 %; Price per board foot: $6.5 /board ft. Results — Board feet per piece = 4 board ft; **Total board feet = 40 board ft**; Board feet to buy (with waste) = 46 board ft; Total linear feet = 80 ft; Estimated cost = $299.00. ## Key terms - **Board foot**: A volume of 144 cubic inches (1 in × 12 in × 12 in), about 2.36 litres. - **Nominal size**: The rough-sawn size used to name lumber; a nominal 2×4 is actually 1½ × 3½ in after drying and planing. ## FAQ **How many board feet are in a 2×4 that is 8 feet long?** 2 × 4 × 8 ÷ 12 = 5.33 board feet using nominal sizes. Lumber yards selling dimensional lumber by the piece usually ignore board feet, but hardwood dealers price by them. **What is 4/4, 5/4 and 8/4 lumber?** Rough hardwood thickness in quarter inches: 4/4 is 1 in, 5/4 is 1¼ in, 6/4 is 1½ in and 8/4 is 2 in. Use these nominal numbers for board feet. **How many board feet are in a cubic foot?** Twelve, because a cubic foot is 1,728 in³ and a board foot is 144 in³. **Why add waste?** Knots, checks, snipe and offcuts usually cost 15–30% of rough hardwood; furniture makers often allow even more. **What formula does the Board Foot Calculator use?** Board feet = thickness (in) × width (in) × length (ft) ÷ 12. ## Sources - [USDA Forest Products Laboratory – Wood Handbook](https://www.fpl.fs.usda.gov/documnts/fplgtr/fpl_gtr282/fpl_gtr282.pdf)