From board feet to a lumber order

Choose the right dimensions

A board foot measures volume: 144 cubic inches. With thickness and width in inches and length in feet, calculate T × W × L / 12. If length is also in inches, divide by 144 instead. Quantity multiplies the result after the volume of one board is calculated.

In hardwood descriptions, 4/4 means one inch of nominal thickness, 5/4 means 1.25 inches and 8/4 means two inches. Surfacing removes material, so a finished board can measure less. For a buying estimate, ask which thickness, width and length the yard uses for billing. For the physical volume of a board you already own, measure its actual dimensions.

The calculator does not know whether an input is rough, nominal or finished. For example, a board entered as 1 × 6 × 8 feet gives 4 BF; entering a measured thickness of 3/4 inch gives 3 BF. Neither answer establishes what a seller should charge. Similarly, the nominal label on construction lumber is not its measured cross-section. Do not switch between nominal and actual dimensions in the middle of an estimate.

The thickness buttons enter numeric inch values; in metric mode they enter their centimetre equivalents. To enter a three-quarter-inch measured thickness, use 3/4. Use the 4/4 button for a nominal one-inch thickness rather than typing 4/4 as a mathematical fraction.

Price one board

Assume a supplier quotes a 4/4 board at $5.80 per BF and uses a 1-inch billed thickness, 6-inch width and 8-foot length. These prices are invented examples, not current lumber-market rates.

1. In the calculator, select in / ft. Enter thickness 1, width 6, length 8 with ft selected, and quantity 1.
2. Enter 5.80 in Price per board foot. The volume is 1 × 6 × 8 / 12 = 4 BF, and its cost is 4 × $5.80 = $23.20.
3. For four matching boards, change quantity to 4: the per-board result stays 4 BF, while total footage becomes 16 BF and cost becomes $92.80.
4. Name the row "Shelf stock" and add it to the cut list. A list row describes stock of one size, not a guaranteed finished shelf or an optimized cutting layout.

Length is easy to misread. An entry of 8 with inches selected is only eight inches long; 96 inches is the same as eight feet. When comparing another calculator's result, check the unit selector before assuming its formula is different.

Build a mixed project and add waste

Keep the shelf row and add "Rail stock": thickness 2, width 4, length 6 ft, quantity 2, price 8.00 per BF. This second row has a different thickness and price, so it must be calculated separately.

With 15 in Waste allowance, the calculator scales net footage by 1.15: 24 × 1.15 = 27.60 BF. The proportional priced cost is $156.80 × 1.15 = $180.32. The default 15% is only a starting assumption. Defects, short usable sections, grain matching and your cutting layout can change how much extra stock is needed.

Why the Buy count and cost are different estimates

The Buy count adds whole pieces separately per row: 4 + ceil(4 × 0.15) = 5 shelf boards, and 2 + ceil(2 × 0.15) = 3 rail boards, for 8 boards. Those eight boards total 32 BF. At the example prices they would cost 5 × $23.20 + 3 × $32.00 = $212.00, not $180.32. The displayed Cost with waste is proportional; it is not a quote for the rounded whole-piece count.

The BF view shows a rounded-up footage purchase estimate, ceil(27.60) = 28 BF, but that does not ensure the available boards have the widths and lengths your project needs. A long part cannot be made from several short offcuts just because their combined volume is sufficient.

Unpriced rows and rounding

If a row has no price, the optional Default $/BF can supply one. Without either price, that row contributes volume but no cost; the page labels a partial estimate "priced boards only". Check that every row you want included in the budget is priced. Costs use the supplied rate only: sales tax, delivery, minimum orders and machining charges are not added.

Project totals are accumulated at full precision before rounding. Displayed row totals are balanced to match the rounded project total. A yard may round each board, measure widths differently or apply a minimum charge, so its invoice can differ even when the underlying volume formula agrees.

Check a metric entry

Select cm and enter thickness 2.54, width 15.24, length 243.84, quantity 1. These are the exact centimetre equivalents of 1 inch × 6 inches × 8 feet. The calculator again gives 4 BF. All three metric dimensions are in centimetres, including length; entering 2.4384 as the length would mistake metres for centimetres.

The conversion follows the exact definition 1 inch = 0.0254 metres: one BF = 144 × 0.0254³ = 0.002359737216 m³, so one cubic metre is approximately 423.776 BF. The engine returns a four-decimal volume of 0.0094 m³ for this board; the page displays at most three decimals, showing 0.009 m³. Neither rounded value is used to derive its board footage.

Switching units clears dimension inputs and the cut list rather than converting an existing project. Print or export your list first; if you switch by mistake, Undo restores the previous list and units. The price remains per board foot, not per cubic metre. To convert a quote of $1,000 per m³ to the expected input, multiply by 0.002359737216, giving about $2.359737216 per BF. The dollar sign is a display convention; there is no currency conversion.

Compare the yard's quote before ordering

• Confirm species, grade, thickness, moisture condition and whether stock is rough or surfaced. These affect usefulness and price but are not calculator inputs.
• Confirm billed dimensions and whether the yard rounds footage per board or across the order.
• Check that boards have enough usable length and width for each part after trimming, joinery and saw kerf. The cut list does not optimize nesting or cuts.
• Compare priced and unpriced rows, waste allowance and whole-piece rounding separately.
• Ask about tax, delivery, surfacing and minimum purchase charges before treating the estimate as a budget.
• Keep a dated printout or CSV/JSON export. A saved browser session is convenient, but clearing site data removes it.

Methodology and corrections

These worked numbers are original examples calculated using the same engine as the tool and covered by regression tests. The methodology page describes the automated checks and excluded factors. For background on timber products and measurement, see the USDA Forest Products Laboratory's Wood Handbook; supplier-specific billing still needs confirmation.

Report an unclear explanation or a conflicting result through Contact, including dimensions, units, quantity, price and the result you expected. Read Privacy before sharing a project link, which contains readable project data.

Use these steps in the calculator