Calculation method
For each board, multiply thickness in inches by width in inches by length in inches, then divide by 144. Multiply by the number of boards and by the USD price per board foot. Use the dimension basis used by the seller.
Worked example: input to purchase quantity
One 1.5 in × 5.5 in × 8 ft board is 5.5 BF. Four boards are 22 BF. At $3 per BF, the total is $66.
This calculator supports lumber board-foot purchasing. Enter thickness and width in inches, length in feet, number of boards, and a price in US dollars per board foot. The arithmetic uses the values you provide and displays the purchase result alongside the intermediate amount. The output is intended for a measured planning worksheet; it does not replace a project drawing or product specification.
Measure and choose the correct input
Read the supplier’s dimensions and distinguish a nominal trade name from the dressed measurement of the physical board. Nominal 2×6 lumber can measure about 1.5×5.5 inches after dressing; some sellers still price from nominal tally. The invoice basis wins over a guessed dimension.
How the estimate is calculated
Board feet per piece = thickness × width × length in inches ÷ 144; total board feet = per-piece result × quantity; cost = total board feet × unit price. With 1.5 inches of thickness, 5.5 inches of width, and 96 inches of length, 1.5 × 5.5 × 96 ÷ 144 = 5.5 BF. Four equal pieces are 22 BF; at $3 per BF the material subtotal is $66. Sales tax, delivery, and cutting charges are separate.
Verify the order
Compare the calculator volume with a second hand calculation for one piece. Confirm whether the seller bills actual dimensions or a nominal tally before comparing the calculated cost with a quote. Ask for species, grade, actual surfaced size, stock length, price basis, and whether the listed price applies per board foot or per piece. Record each line item separately when dimensions or rates vary.
Where the model ends
This volume estimate does not select a strength grade, span, species, moisture condition, waste allowance, or cut list. Keep that limitation visible when using the quantity for a real purchase.
Keep a traceable worksheet
A useful order begins with a dated sketch, a product name, and dimensions recorded in their original units. Mark each repeated element so that its count can be checked against the site. Record where each figure came from: a tape measure, a plan, a supplier listing, or a design detail. This makes later changes auditable. If two sections differ, estimate them separately before adding the purchase quantities. A single average may hide a small but important difference at a boundary.
Read the result in stages
The calculator shows intermediate quantities so the final purchase count can be checked. Work through the displayed values in order instead of treating the last number as a guarantee. Keep full precision during the calculation and round only where the model says a purchasable whole item is required. A value just over a whole item still requires another item. If the answer changes after switching units, check whether converted entries were rounded in the form or whether a product-specific unit was assumed.
Separate quantity from design
This worksheet estimates material amounts from chosen project inputs. It cannot inspect the site or decide what assembly is safe and suitable. Structural requirements, local rules, product instructions, drainage, loads, and installation methods belong in the project design. Resolve those matters before treating a material estimate as a purchase list. If the design changes, update the dimensions and parameters and calculate again. Do not use an arbitrary extra percentage to repair an incorrect geometry or unsuitable specification.
Check the seller before paying
Compare the measured result with the unit in which the seller actually quotes and sells material. Check available stock sizes, package quantities, delivery constraints, return terms, and whether a listed size is nominal or actual. A quantity that is mathematically correct can still produce a wrong order when a product is sold by a different unit. Save the product page or label used for the estimate. If the listed yield, dimension, or unit price changes, revise the worksheet rather than reusing an old purchase count.
Product and method reference
Reference limits and default yields are identified separately from user-entered values; verify the adopted local code and current product label. Penn State Extension board-foot valuation.
Calculation and editorial review: November 3, 2026. Arithmetic runs in your browser; project inputs are not submitted to TwoCut.