Board Foot Calculator
Board feet of lumber from length, width, thickness and quantity.
Total board feet
40
4 bf per board
Per board
4 bf
Boards
10
AI Breakdown & Smart Takeaway
Plain-English insight on your numbers
Get a personalized explanation of what these results mean — and how to improve them.
How the Board Foot Calculator works
The Board Foot Calculator helps contractors, woodworkers, and DIYers instantly determine the total volume of lumber needed for a project by converting length, width, thickness, and quantity into board feet (bf) — the standard unit used by lumber yards across North America.
A board foot is a volumetric unit equal to a piece of wood that is 1 inch thick, 12 inches wide, and 12 inches long — essentially 144 cubic inches of lumber. This standard was adopted by the North American timber industry to create a consistent pricing and inventory system regardless of the actual dimensions of a given board. When you enter your lumber's thickness, width, and length into the calculator, it multiplies those three dimensions and divides by 144 (if working in inches) or by 12 (if length is in feet) to produce the board foot count for one piece, then multiplies by quantity for your total.
The key inputs — thickness, width, length, and quantity — each play a distinct role in the final result. Thickness and width are typically measured in nominal inches (the size a board is called at the lumber yard), while actual dressed dimensions are slightly smaller after milling. For example, a '2x4' actually measures 1.5 inches by 3.5 inches, but lumber yards price and sell by the nominal dimension. This calculator uses the dimensions you enter as-is, so it's important to decide whether you're pricing from a yard quote (use nominal) or estimating actual wood volume for joinery work (use actual/dressed dimensions).
One of the most common mistakes when calculating board feet is failing to account for waste. Cutting, planing, jointing, and routing all remove material, and defects like knots or warping often require you to cut around problem areas. A professional rule of thumb is to add 15–20% overage to your calculated board feet for furniture or finish carpentry, and 10% for rough framing where precision cuts are fewer. If you're working with figured or exotic timber where waste can be higher, 25–30% overage is not uncommon. This calculator gives you the raw bf total — always apply your waste factor before ordering.
When ordering from a lumber yard, board feet are used to calculate cost: the price per board foot ($/bf) multiplied by total board feet gives your material estimate. Prices vary significantly by species — common softwoods like pine or Douglas fir run $1–$3/bf, while hardwoods like walnut or cherry can exceed $10–$20/bf. Using this calculator with accurate dimensions and realistic quantities before you visit a supplier helps you compare quotes, avoid over-ordering expensive material, and budget confidently for your project.
Formula
Board feet = (Length_ft × Width_in × Thickness_in) / 12
Pro tips
- Always clarify with your lumber supplier whether they price by nominal or actual dimensions — most North American yards use nominal, but hardwood dealers sometimes charge by actual thickness, especially for thicker slabs.
- For large projects, group your cut list by species and thickness before calculating total board feet; this makes ordering more efficient and helps you take advantage of bulk pricing tiers.
- Add a 15–20% waste factor for finish carpentry and furniture projects, and at least 10% for framing — never order exactly what your bf calculation returns or you risk running short mid-project.
- When comparing lumber prices between suppliers, always convert to a cost-per-board-foot figure; a lower sticker price on a shorter board can actually be more expensive per bf than a longer piece from another yard.
- If you're working with S4S (surfaced four sides) lumber for joinery, use the actual dressed dimensions in your calculation to get a true volume figure for your wood movement and glue-up planning, even if you use nominal dimensions for purchasing.
Key terms
- Board Foot (BF)
- — A unit of lumber volume equal to 144 cubic inches, representing a board 1 inch thick, 12 inches wide, and 12 inches long.
- Nominal Dimension
- — The named size of a lumber piece as sold at the yard (e.g., 2×4), which is larger than the actual milled dimension after drying and surfacing.
- Actual (Dressed) Dimension
- — The true measured size of a board after milling and surfacing, always smaller than the nominal dimension — a nominal 2×4 is actually 1.5" × 3.5".
- Linear Foot
- — A one-dimensional length measurement of lumber (12 inches), used for pricing molding or trim, as opposed to board feet which account for volume.
- Waste Factor
- — An overage percentage added to the calculated board foot total to account for cutting losses, defects, and material spoilage during a project.
- Rough Sawn Lumber
- — Lumber cut directly from a log without surfacing, sold closer to its true nominal dimension and commonly priced and measured in board feet.
