Lumber Cost Calculator

Background.

A lumber cost calculator answers the question a board-feet calculation alone does not: what will this order actually cost at the register? Board feet is the standard unit lumber is bought and sold by in the United States, defined by the USDA Forest Products Laboratory's Wood Handbook as 144 cubic inches — the volume of a board one inch thick, one foot wide, and one foot long. Knowing the board-foot quantity of a project is the first step, but a real purchase also needs a waste allowance for cutoffs and defects, sales tax, and often a delivery or handling fee before the number on the receipt matches the number in the budget. This calculator computes all of it in one pass: board feet per piece, total board feet, waste-adjusted board feet to order, material subtotal, sales tax, and a final total cost.

This calculator is deliberately not a duplicate of the existing Board Foot Calculator on this site. That calculator focuses on the underlying unit-of-measure conversion — board feet, cubic feet, and cubic inches from a board's dimensions — and includes an optional flat material cost. This calculator instead starts from the assumption that you already know you need lumber and are trying to budget an actual purchase: it adds a waste allowance as a first-class input, layers sales tax on top of the material subtotal, and adds a flat delivery or handling fee, with the total purchase cost as the headline result rather than the board-foot quantity. If you only need the raw board-foot or cubic-foot conversion without the purchasing layer, use the Board Foot Calculator instead; if you are trying to answer "what will I actually spend," this calculator is the right tool.

One detail this calculator handles explicitly, because general-purpose lumber tools often gloss over it, is the distinction between nominal and actual board dimensions. A board sold and labeled as a "2x6" is not actually 2 inches by 6 inches after milling — the dressed, finished size is closer to 1.5 by 5.5 inches, because the rough-sawn board loses material during surfacing. Despite that, the lumber trade prices and measures board footage using the nominal dimensions, not the smaller dressed dimensions, a convention documented in the National Hardwood Lumber Association's grading rules for measuring and inspecting lumber. That is why this calculator's thickness and width inputs default to nominal sizes like 2 and 6 for a "2x6" board — entering the smaller dressed dimensions would understate the board footage and, ultimately, the price a supplier actually charges.

Waste allowance is included as an editable input rather than folded silently into the price, because the right percentage varies by project: a straightforward framing run with few cuts might need only 5 percent, while a project with many angle cuts, joints, or a higher defect rate in the specific grade of lumber purchased might reasonably need 10 to 15 percent or more. Sales tax and delivery fee are also both editable and both optional, since tax rates vary enormously by jurisdiction and many lumber yards either include delivery in the unit price or charge a flat fee that has nothing to do with the board-foot quantity ordered. Keeping these as separate, visible inputs — rather than hidden constants — means the final total cost stays auditable line by line, from raw board feet through to the number a supplier would actually invoice.

What is lumber cost calculator?

A board foot is the standard unit of lumber volume in the United States, equal to 144 cubic inches — the volume of a board one inch thick, one foot wide, and one foot long. For a board measured in inches and feet, board feet per piece is calculated as thickness (inches) times width (inches) times length (feet), divided by 12. The USDA Forest Products Laboratory's Wood Handbook and the National Hardwood Lumber Association's grading rules are the standard references for this definition and its use in lumber pricing.

This calculator extends the basic board-foot calculation into a full purchase estimate. It multiplies board feet per piece by the number of boards to get total board feet, applies a waste percentage to account for cutoffs and defects, multiplies the result by a price per board foot to get a material subtotal, applies a sales tax rate, and adds a flat delivery or handling fee to arrive at a total purchase cost.

Board footage in the lumber trade is conventionally measured and priced using nominal dimensions (the size a board is labeled and sold as, such as "2x6"), not the smaller actual dressed dimensions after milling (roughly 1.5 by 5.5 inches for a nominal 2x6). This calculator's thickness and width inputs are intended as nominal dimensions to match standard lumber-yard pricing practice.

How to use this calculator.

1. 01Enter the board's nominal thickness and width in inches, and its length in feet.
2. 02Enter the number of boards needed for the project.
3. 03Enter a waste allowance — a higher percentage for projects with many cuts or a lower-grade lumber selection.
4. 04Enter the price per board foot quoted by your supplier.
5. 05Optionally enter a sales tax rate and a flat delivery or handling fee.
6. 06Read board feet per piece and total, the waste-adjusted board feet to order, the material subtotal, sales tax, and the total purchase cost.

The formula.

Board feet per piece is thickness in inches times width in inches times length in feet, divided by 12 — the standard board-foot formula from the USDA Forest Products Laboratory's Wood Handbook. For a nominal 2x6x8 board, that is 2 times 6 times 8, divided by 12, or 8 board feet per piece.

Total board feet before waste is board feet per piece multiplied by the number of boards. For 20 boards at 8 board feet each, that is 160 board feet. The waste-adjusted board feet to order applies the waste percentage: total board feet multiplied by (1 plus waste percent divided by 100). At a 10 percent waste allowance, 160 board feet becomes 160 times 1.10, or 176 board feet — the actual quantity a supplier should be asked to supply, since a straight 160-board-foot order would likely run short once cutoffs and defective pieces are accounted for.

The material subtotal is the waste-adjusted board feet multiplied by the price per board foot. At $1.10 per board foot, 176 board feet costs 176 times 1.10, or $193.60. Sales tax is the material subtotal multiplied by the tax rate: at 7 percent, that is 193.60 times 0.07, or $13.552. The total purchase cost adds the material subtotal, sales tax, and any flat delivery fee together: 193.60 plus 13.552 plus a $25 delivery fee equals $232.152, rounding to $232.15 at the register.

A worked example.

Frequently asked questions.

References& sources.

1. [1]USDA Forest Products Laboratory (2021). Wood Handbook: Wood as an Engineering Material, FPL-GTR-282.
2. [2]National Hardwood Lumber Association (2023). NHLA Rules for the Measurement & Inspection of Hardwood & Cypress Lumber.
3. [3]National Institute of Standards and Technology (2026). NIST Handbook 133, Appendix E: General Tables of Units of Measurement.