How do I calculate board feet?
Multiply thickness in inches by width in inches, length in feet and piece count, then divide by 12. A board foot is 144 cubic inches of lumber volume. Ten pieces measuring 2 × 6 inches and 8 ft long total 80 board feet by those entered dimensions. At $5 per board foot, the estimate is $400.
Board feet measure volume, not board count
A board foot combines thickness, width and length. It is useful when a lumber price is quoted per board foot instead of per piece or per linear foot. The same total can describe a few thick boards or more thin ones. It does not identify the number of usable parts that can be cut from the timber.
This board foot calculator assumes every piece in the entry has the same dimensions. Calculate separate groups for mixed widths, thicknesses or lengths. Add their unrounded board-foot totals for a combined geometric volume. Supplier invoices may apply their own tally rules, which should be checked before using that total as a purchase quote.
Board foot formula with inches and feet
Board feet per piece = thickness in inches × width in inches × length in feet ÷ 12. Total board feet = board feet per piece × number of pieces. For lengths measured entirely in inches, divide thickness × width × length by 144 instead. Mixing those two denominators is a common source of a twelvefold error.
Metric mode accepts thickness and width in millimeters and length in meters, then converts the result to board feet. The output remains a board-foot measure; switching units does not change the definition. One board foot is exactly 0.002359737216 m³, based on the inch and foot conversions used by the calculator.
Nominal versus actual lumber dimensions
Choose dimensions according to the question you want to answer. To estimate physical wood volume, use measured dimensions. To reproduce a seller’s quoted board-foot price, use that seller’s measurement convention. A nominal label and a finished measurement can produce different totals without either calculation being an arithmetic error.
For ten 8-ft pieces, entering 2 × 6 inches gives 80 board feet. Entering 1.5 × 5.5 inches gives 55 board feet. That 25-board-foot difference comes entirely from the dimensions supplied. The tool does not automatically translate a nominal 2 × 6 into a finished size.
Worked example: lumber volume and price
One piece measuring 2 inches thick, 6 inches wide and 8 ft long contains 2 × 6 × 8 ÷ 12 = 8 board feet. Ten identical pieces contain 80 board feet. At an entered rate of $5 per board foot, the lumber subtotal is 80 × $5 = $400.
The same ten pieces have 80 linear feet of total length, but that numerical match is a coincidence of the chosen dimensions. Ten 1 × 6 pieces of the same length still have 80 linear feet but only 40 board feet. Keep the unit label beside the number when comparing supplier quotes.
| Dimensions per piece | Pieces | Board feet | Total linear length |
|---|---|---|---|
| 1 × 6 in × 8 ft | 10 | 40 | 80 ft |
| 2 × 6 in × 8 ft | 10 | 80 | 80 ft |
| 1.5 × 5.5 in × 8 ft | 10 | 55 | 80 ft |
Compare per-piece and per-board-foot prices
To compare a piece price with a board-foot rate, divide the piece price by the board feet calculated under the same dimension convention. For example, a $40 piece containing 8 board feet implies $5 per board foot. This comparison is meaningful only when the material specification and pricing basis also match.
The entered price produces a material subtotal. It excludes delivery, tax, machining, grading premiums and other line items unless you incorporate them in your own rate. A geometric volume also does not tell you how many clear, defect-free parts the boards will yield. Keep cutting allowance and usable-part planning separate from the volume calculation.
Use the right lumber measure for the next task
Download the estimate with thickness, width, length and piece count so the price calculation can be repeated. When a supplier uses board-foot rounding or a bundle tally, compare their method explicitly rather than adjusting dimensions until two totals happen to match. Record whether your figures are nominal or measured.
For a deck surface, the deck material calculator counts stock boards and their layout instead of lumber volume. For a fence, the picket, post and rail calculator counts components. Read the deck materials guide to keep surface coverage, stock length and material cost on separate lines.
The American Hardwood Export Council defines board feet using thickness and width in inches and length in feet. Supplier tally and rounding conventions can differ from a calculator’s unrounded geometric volume. American Hardwood Export Council measurement guide.
Frequently asked questions
What is the difference between board feet and square feet?
Square feet measure area, such as a deck surface. Board feet measure volume and include thickness. A 1-inch-thick board covering 1 ft² is 1 board foot; a 2-inch-thick piece covering the same area is 2 board feet.
Does 4/4 lumber always measure exactly 1 inch thick?
A quarter-based label describes a lumber thickness convention. The measured finished piece and the supplier’s pricing basis can differ. Enter the dimension that matches your purpose, and confirm the seller’s convention rather than assuming a label is a measured finished thickness.
Can I enter several lumber sizes at once?
This version handles one repeated size per calculation. Calculate each size group, download its estimate and add the board-foot totals. Keep the groups separate if their price per board foot differs.
Written by Velour Trends · Updated 7 November 2026. Worked examples use the calculator’s stated formulas and rounding model. Our editorial approach · Report a calculation issue.