What is a board foot?
A board foot is a unit of volume equal to a board 1 inch thick, 12 inches wide, and 1 foot long. That is 144 cubic inches. Different shapes can contain the same number of board feet: a 1-inch × 6-inch × 2-foot board also contains one board foot.
If your length is in inches, use thickness × width × length ÷ 144. Multiply the result by the number of identical boards. The calculator converts inch lengths to feet before applying the formula.
A worked lumber tally
Suppose you are buying four boards, each entered as 1 inch thick, 6 inches wide, and 8 feet long.
- One board: 1 × 6 × 8 ÷ 12 = 4 BF.
- Four boards: 4 × 4 = 16 BF.
- At $6.50 per BF: 16 × $6.50 = $104.00, before other charges.
| Thickness × width × length | Quantity | Total BF |
|---|---|---|
| 1 in × 6 in × 8 ft | 1 | 4 |
| 3/4 in × 8 in × 6 ft | 2 | 6 |
| 1 1/2 in × 8 in × 10 ft | 3 | 30 |
Which dimensions should you enter?
For a physical-volume estimate, enter the thickness and width you measured. For a purchasing estimate, ask the supplier which dimensions it uses to tally and price lumber. Rough thickness, surfaced measurements, nominal sizes, and tally practices are not interchangeable.
For example, entering 2 × 4 × 8 gives 5.3333 BF. Entering measured dimensions of 1.5 × 3.5 × 8 gives 3.5 BF. The formula is consistent; the inputs describe different volumes. Neither result establishes how the seller will price that board.
Questions from the workbench
Are board feet the same as linear feet?
No. Linear feet measure length. Board feet measure volume, so thickness and width are required. An 8-foot board can contain many different volumes depending on its cross-section.
Can I enter a mixed list of sizes?
Yes. Choose “Add board size” for each different thickness, width, or length. Quantity applies only to that row. Each row’s volume is calculated before the full list is added together.
Does this automatically add waste?
No. The result includes only the boards in your list. Add the extra boards you expect to purchase. A generic percentage cannot determine whether a specific cutting plan will fit.
Why does the supplier’s total differ?
Ask about tally dimensions, measurement increments, minimums, and rounding. This tool calculates unrounded geometric volume and rounds only for display. Supplier billing may use another convention.
Are my measurements saved?
No. Entries are calculated in your browser, are not uploaded by this calculator, and disappear when you reload or leave the page. Print a tally if you want to keep a copy.
Check the calculation
Results are displayed to four decimal places, with trailing zeros removed. Costs are displayed to two decimals and calculated from the unrounded volume. Tiny positive results below 0.0001 BF are labeled as such. See our calculation methodology and the board-foot purchasing guide for the assumptions behind this tool.