Lumber Calculator

A material list often mixes three useful but different quantities: board feet describe a nominal wood volume, linear feet describe total length, and pieces describe countable stock. This calculator shows all three so a cut list can be checked from more than one angle. They should not be treated as interchangeable without the dimensions and stock lengths that connect them.

Board Foot and Cost modes use the nominal width and thickness in the formula. The page also displays an actual-size lookup for common dimensional lumber, but that lookup does not change the calculation. For example, the tool treats a nominal 2 by 4 as 2 in by 4 in when calculating board feet, while its reference text displays 1.5 in by 3.5 in as a typical milled size. Confirm the actual product label at the supplier, especially for surfaced, treated, engineered, imported, or specialty products.

The USDA Forest Products Laboratory's commercial-lumber reference is useful context: lumber sizes, grades, and availability are product and market facts, not values a quantity calculator can decide.

For Board Foot and Cost modes, the calculation is explicit:

The denominator of 12 comes from the traditional board-foot unit: one inch by twelve inches by one foot. NIST's unit tables support the inch, foot, and volume relationships used in that arithmetic. The formula is a quantity convention, not a statement of structural capacity or a substitute for a supplier's grade and product information.

The Framing Lumber mode is deliberately simpler than a wall layout. It calculates base positions as ceil(wall length in inches ÷ spacing) + 1, adds three studs for each corner you enter and two studs for each opening you enter, then applies the allowance. It uses the stock stud length and nominal size you select to derive linear feet and board feet.

This is a preliminary stock-count model only. It does not know the actual position, width, height, or framing arrangement of an opening; it does not separate king, jack, cripple, trimmer, backing, blocking, braced-wall, or connection requirements; and it cannot decide whether 16 in or 24 in on-center spacing, a 2 by 4 or 2 by 6, or any framing configuration is appropriate. Use the more detailed Stud Calculator only after a wall design has been selected, and verify the final design under the locally adopted rules and project documents.

Deck Board mode first takes the listed actual width for the chosen board and adds the entered gap. It divides deck width in inches by that effective width and rounds up to whole board runs. It then multiplies runs by the entered board-run length, applies the allowance, and rounds up to the selected stock length.

For the page's 20 ft by 12 ft example with 5/4 by 6 boards, 1/8 in gap, 12 ft stock, and 10% allowance, the tool uses a 5.5 in actual width plus 0.125 in gap = 5.625 in. It calculates 26 runs, 520 raw linear feet, 572 adjusted linear feet, and 48 stock boards. It does not create a board-joint plan, account for a picture frame, decide fastener spacing, or evaluate joists, beams, footings, rails, or connections.

For a job-level board, framing, hardware, and cut-list workflow, use the separate deck material takeoff guide. Keep structural design and product installation requirements outside this coverage arithmetic.

An allowance is not a repair for an undefined material list. First write the raw list: member or board type, nominal size, actual product if known, finish length, stock length, count, and where offcuts can be reused. Then decide whether extra material is justified by end cuts, non-reusable offcuts, defects, selected stock lengths, matching, pattern work, or a future repair piece. Record that reason next to the percentage.

The Custom Cut List mode is useful for a mixed tally, but read its cost output carefully. The page sums the price entered for each raw row; it applies the allowance to displayed board feet and linear feet, not automatically to the custom-row cost. Add the cost of extra stock deliberately after you decide what extra pieces will actually be purchased.

Use a current supplier quote for the final check. Price per board foot, per linear foot, and per piece are different units, and a price total cannot see tax, delivery, handling, treatment, hardware, or labour unless those values are separately recorded.

This calculator cannot choose a species, grade, member size, span, connection, fastener, treatment, fire or decay rating, decking product, framing layout, or safe cutting and installation method. The 2024 IRC's wall-framing provisions, where adopted, show why those decisions depend on much more than a count: wall height, load, bracing, openings, connections, and local conditions matter. The applicable code may be a different edition or locally amended, and it is not automatically the right standard for every project or location.

Before ordering, compare the output against the approved list and supplier product data. If a total looks high or low, check nominal versus actual dimensions, stock length, unit price, allowance, board direction, and whether a structural member was accidentally treated as finish lumber. You can also report a calculator issue or unclear result so the site team can review it.