Board Feet Lumber Calculator
Calculates total board feet of lumber needed for a project, including a waste factor for cuts and defects. Use it when estimating material quantities and costs at the lumber yard.
About this calculator
A board foot is the standard North American unit of lumber volume equal to 144 cubic inches — equivalent to a board 12 inches wide, 12 inches long, and 1 inch thick. To find board feet for any piece, multiply its three dimensions in inches and divide by 144: boardFeet = (length × width × thickness) / 144. When buying for a project you must account for waste from saw kerfs, end trimming, and defect cutouts. The full formula used here is: totalBoardFeet = ((length × width × thickness × quantity) / 144) × wasteFactor. A wasteFactor of 1.0 means no waste allowance; 1.15 adds 15% extra, which is typical for straight cuts on clear lumber; 1.25 or higher is appropriate for figured wood with frequent defects. All dimensions must be entered in inches. Note that lumber yards sell by nominal dimensions (e.g., a 2×4 is actually 1.5 × 3.5 inches), so always use actual measured dimensions for accurate results.
How to use
Project: you need 6 pieces of walnut, each 36 inches long, 5 inches wide, and 1 inch thick, with a 20% waste allowance. length = 36, width = 5, thickness = 1, quantity = 6, wasteFactor = 1.20. Step 1 — raw volume: 36 × 5 × 1 × 6 = 1,080 cubic inches. Step 2 — convert to board feet: 1,080 / 144 = 7.5 BF. Step 3 — apply waste factor: 7.5 × 1.20 = 9.0 board feet. If walnut costs $12 per board foot at your lumber yard, budget 9.0 × $12 = $108. Always round up to the nearest whole board foot when ordering — most suppliers sell in whole-foot increments.
Frequently asked questions
What is a board foot and how is it different from a linear foot of lumber?
A board foot measures volume — specifically 144 cubic inches — and accounts for a board's width and thickness as well as its length. A linear foot measures only length, ignoring how wide or thick the board is. Lumber is priced in board feet because a 1-inch-thick plank and a 2-inch-thick plank of the same length represent very different amounts of raw material. To convert: one linear foot of a 1×6 board equals 0.5 board feet (12×6×1/144), while one linear foot of a 2×6 equals 1.0 board feet (12×6×2/144).
How much waste factor should I add when buying lumber for a woodworking project?
A 10–15% waste factor (1.10–1.15) is typical for projects using straight-grained, clear lumber with minimal defects and mostly rip or cross cuts. Increase to 20–25% (1.20–1.25) when working with figured or knotty lumber where you must cut around defects, or when your design requires many short pieces that leave long offcuts. Parquet flooring and small-part projects like boxes often need 30% or more because the efficient nesting of parts is limited. It is always cheaper to buy slightly too much upfront than to make a special trip to the lumber yard for a few extra board feet, especially with species that vary in color and grain between purchase dates.
Why should I use actual dimensions instead of nominal lumber dimensions in the board feet formula?
Nominal dimensions are the rough-sawn size a board starts at before drying and surfacing at the mill, but the lumber you buy has already been dried and planed to a smaller actual size. A nominal 2×4 measures 1.5 × 3.5 inches, a 1×6 measures 0.75 × 5.5 inches, and so on — each dimension is roughly 1/4 to 1/2 inch smaller than the nominal label. Using nominal dimensions overstates the volume you are actually receiving by 10–20% and leads to underestimating how many pieces you can cut from a board. Always measure the board in hand or look up the standard actual size for the nominal designation you are buying.