Board Feet Lumber Calculator
Board feet of lumber from thickness, width, and length
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What this calculator computes
The board-feet calculator converts the dimensions of a single piece of lumber, or a quantity of identical pieces, into board feet, the volume unit used by US sawmills, hardwood dealers, and furniture-grade lumber yards. One board foot equals 144 cubic inches, the volume of a 1-inch thick by 12-inch wide by 12-inch long board (1 × 12 × 12 = 144 in³). The formula is bf = (T × W × L) / 144 when the dimensions are in inches, or bf = (T × W × L) / 12 when the length is in feet (the most common convention). Inputs are nominal thickness (e.g., 4/4 for 1-inch nominal hardwood, which actually measures 0.75 inch dry; 8/4 for 2-inch nominal, etc.), width in inches, length in feet, and the quantity of pieces. The calculator returns the total board feet, useful for both pricing (hardwood is sold per board foot) and waste-planning (rough lumber is bought 25–30% over net dimensions to account for jointing, planing, and defect removal). Hardwood lumber is typically rough-sawn and sold by the board foot from sawmills and specialty dealers; softwood construction lumber is sold by the linear foot in standard nominal sizes (2x4, 2x6, etc.) and the board-foot calculation is mostly relevant for cabinet, furniture, and millwork projects where rough lumber is dressed in-house.
Calculator
The formula
Formula
board_feet = (thickness × width × length_feet × pieces) / 12
Worked example
When to use this calculator
Use this calculator any time you are pricing or ordering hardwood lumber from a sawmill, a hardwood specialty dealer, or planning a furniture, cabinetry, or millwork project where rough lumber needs to be sized into a finished cut list. The most common cases are furniture-making (where the bill of materials is converted to total board feet for pricing and rough lumber waste planning), cabinet door and face-frame fabrication, custom moulding and trim runs, decking material orders for non-standard widths, and turning and woodworking blanks where the per-board-foot price varies by species and grade. Construction lumber (2x4, 2x6, 2x8) is typically sold by the linear foot rather than the board foot, but the board-foot calculation is still relevant for engineered-lumber and timber-frame applications. The calculator does not handle plywood, MDF, or other sheet goods, which are sold by the sheet (typically 4 × 8 ft or 1220 × 2440 mm).
Common input mistakes
- Using actual (dressed) dimensions instead of nominal. A "1-inch" board (4/4 hardwood or 1x in softwood) is actually 0.75 inch thick after planing and jointing, and a "2x4" is actually 1.5 × 3.5 inch. Board feet always use nominal dimensions for pricing because that is how the lumber was rough-sawn at the mill before dressing. Using actual dimensions under-counts the volume by roughly 25%.
- Confusing board feet with square feet or linear feet. Linear feet measures length only (a 10-foot 2x4 is 10 linear feet); square feet measures area (10 ft² of decking surface); board feet measures volume (10 ft of 1×12 is 10 board feet, but 10 ft of 2×12 is 20 board feet because of the doubled thickness). Mills and dealers price differently by unit, so confirm which unit a quote uses.
Frequently asked questions
What is a board foot?
A board foot is the volume of a piece of lumber 1 inch thick, 12 inches wide, and 12 inches long — equal to 144 cubic inches or about 2.36 litres. Hardwood mills and furniture-grade dealers price by the board foot, with prices varying by species and grade from about $3/bf for poplar to $12+/bf for figured walnut and exotic woods. Softwood construction lumber is more often priced by the linear foot or per-piece, but board foot calculations still apply where engineered components or timber-frame applications are involved.
How do I calculate board feet?
Multiply nominal thickness (inches) by nominal width (inches) by length (feet), then divide by 12. A 1 × 6 × 8 board is (1 × 6 × 8) / 12 = 4 board feet. For multiple identical pieces, multiply by the number of pieces. The dividing factor changes if all dimensions are in inches: divide by 144 instead of 12. Use nominal (rough-sawn) dimensions, not the actual dressed sizes after planing.
Why use nominal dimensions instead of actual?
Lumber is rough-sawn at the mill at the nominal dimension (1 inch, 2 inches, etc.) and then planed down to the dressed dimension (0.75 inch, 1.5 inches) at the dealer or job site. The board-foot price was set when the piece was still the rough-sawn nominal size and reflects the volume of wood the mill harvested from the log. Using dressed dimensions for pricing would shortchange the mill by about 25% on every transaction, so the trade convention universally uses nominal.
How much waste should I plan for hardwood projects?
Plan for 25–35% rough-lumber waste on furniture-grade projects: jointing one edge straight, planing both faces flat, ripping to width, cross-cutting to length, and removing defects (knots, sapwood, checks) all reduce yield. Highly figured species like quilted maple and curly walnut have lower yield (35–40%) because of grain-direction sorting. Long, wide, clear hardwood components (table tops, panel doors) drive yield down further. Order accordingly — running short forces a second mill trip and risks colour-grain mismatches.
How does this differ from softwood construction lumber pricing?
Softwood dimensional lumber (2x4, 2x6, 2x8, 2x10) is sold per piece or per linear foot at most home centres and lumber yards, with prices set by the standard length increments (8, 10, 12, 14, 16 ft). Board-foot pricing is rare for softwood unless ordering rough timbers or engineered components. Hardwood is almost universally board-foot-priced because widths and lengths are not standard — every board off the sawmill is a different size, and per-board-foot pricing is the only way to handle the variety.