Board Calculator
Lumber is priced by volume, but it is sold in named sizes that are not the sizes the wood actually measures. That gap is where board foot calculations go wrong: use the wrong dimensions and you either run short mid-project or pay for wood you never needed. The question this page answers is the order question: how much lumber, in board feet, do these pieces add up to, what should you actually order once waste is counted, and what will it cost?
The board calculator below takes thickness, width, length, number of pieces, a waste factor and an optional price per board foot, and returns board feet per piece, the total, the with-waste order quantity, board feet per linear foot, total linear feet, cubic volume and the estimated cost. A second mode runs the problem backwards: tell it how many board feet a project needs and what each board holds, and it tells you how many boards to buy. If your question is instead what one board foot should cost, that is a unit-price question, and it is answered on the separate cost per board foot page; this page is about quantity.
Enter thickness, width, length and pieces as positive numbers to calculate.
Tip: run the Board feet mode for one piece first to get its board feet, then switch here.
Enter the required board feet and the board feet per board as positive numbers.
Board feet measure volume, not length: one board foot is 144 cubic inches of wood. Whether to enter nominal or actual dimensions depends on the stock, and the section on the nominal trap below explains which to use when.
Quick Answer
Key takeaways
- A board foot is volume: 144 cubic inches. The formula is thickness (in) x width (in) x length (ft) / 12, or / 144 when the length is in inches.
- Framing lumber is billed on its nominal size, so a 2×6 counts as 2 by 6 even though it measures 1.5 by 5.5 inches. Rough and hardwood stock is billed on measured size. Mixing the two conventions is the single biggest board foot error.
- Waste belongs on the order, not in the project total. This calculator reports both: the net total your project contains, and the with-waste figure you should actually buy.
- Cost is priced on the with-waste quantity, because that is the quantity on the invoice.
How to use the board calculator
Work in the mode that matches your question. Board feet mode starts from dimensions and counts up to a total. Boards needed mode starts from a required total and counts back down to whole boards.
Set the size. Use a preset for standard framing sizes or type custom dimensions. Presets enter nominal sizes, which is how yards bill this lumber.
Enter the length and its unit. Cut lists come in both feet and inches; the calculator switches the divisor (12 or 144) to match, so never convert by hand first.
Add pieces and waste. Pieces are identical boards of the size above. Waste defaults to 10%, the standard starting point for straight work.
Price it if you have a quote. Add the yard’s price per board foot and the cost is worked out on the order quantity. For other material quantities on the same job, the same volume logic drives the concrete volume calculator for footings and slabs.
The board foot formula
A board foot is a piece of wood 12 inches wide, 12 inches long and 1 inch thick, which is 144 cubic inches in any shape. Counting how many of those units fit inside your board gives the formula, and the divisor changes only because the length unit changes.
The calculator also reports two figures most tools skip. Board feet per linear foot, which is (thickness x width) / 12, lets you convert any length of the same stock instantly: a 2×6 runs exactly 1.000 board foot per linear foot, which is why it is the easiest framing size to estimate in your head. Cubic volume converts the order into the unit used for timber, shipping and kiln space, at 12 board feet to the cubic foot.
Worked example: ten 2×6 boards, eight feet long
The calculator is pre-filled with this case: nominal 2×6, 8 feet, 10 pieces, 10% waste, $2.50 per board foot.
| Figure | Value |
|---|---|
| Board feet per piece ((2 x 6 x 8) / 12) | 8.00 BF |
| Total for 10 pieces | 80.00 BF |
| With 10% waste (order this) | 88.00 BF |
| Board feet per linear foot | 1.000 |
| Total linear feet | 80.00 ft |
| Volume | 6.67 cu ft |
| Estimated cost (88.00 x $2.50) | $220.00 |
Run the same boards through Boards needed mode in reverse and the rounding effect shows up clearly. A project needing 100 board feet, bought as 8-board-foot pieces, needs 12.5 boards on paper, which the calculator rounds up to 13 boards, actually supplying 104 board feet. That 4 board feet of overage is not waste in the bad sense: it is the cutting allowance the waste factor would otherwise have to cover, and it is why whole-board rounding should happen before you judge whether the waste percentage is enough.
The nominal vs actual trap, settled
A 2×6 is not 2 inches by 6 inches. It left the saw at roughly that size, then drying and planing brought it to 1.5 by 5.5 inches, the size it measures in your hand. The sizes are defined that way in the American Softwood Lumber Standard (PS 20), published through the National Institute of Standards and Technology system and administered by the American Lumber Standard Committee, and every North American yard works to it. The trap is that both sizes are legitimate inputs, for different jobs.
| Nominal size | Actual size (in) | BF per foot (nominal) | BF per foot (actual) |
|---|---|---|---|
| 1×6 | 0.75 x 5.5 | 0.500 | 0.344 |
| 2×4 | 1.5 x 3.5 | 0.667 | 0.438 |
| 2×6 | 1.5 x 5.5 | 1.000 | 0.688 |
| 2×8 | 1.5 x 7.25 | 1.333 | 0.906 |
| 2×12 | 1.5 x 11.25 | 2.000 | 1.406 |
| 4×4 | 3.5 x 3.5 | 1.333 | 1.021 |
The rule is simple once the billing is understood. Softwood framing lumber is invoiced on nominal board feet, so calculate and compare quotes in nominal: a yard selling you a 2x4x8 charges for 5.33 board feet, whatever the tape measure says. Rough-sawn and hardwood stock is invoiced on measured size, so measure the boards and calculate in actual. And for laying out the project itself (spans, clearances, fit), only actual dimensions exist. Using actual sizes for a framing order understates it by roughly a third, which is how the 2×4 in the table drops from 0.667 to 0.438 board feet per foot. The same nominal-versus-actual discipline shows up in other material estimates, from boards to the asphalt volume calculator for a driveway apron.
How much waste to add
Waste covers saw kerf, end trimming, defects you cut around, and the occasional ruined cut. Ten percent, the default here, suits straight framing and simple shelving. Move up to 15 to 20% for decks and fences with angles or many short pieces, and 20 to 25% or more for hardwood work where you are selecting for grain and cutting around knots and sapwood. Going the other way, a single repeated cut in clean stock can run at 5%. Notice what waste is not for: it does not fix a wrong board count, and it should not be stacked on top of whole-board rounding twice. This calculator keeps the net total and the order quantity as separate lines precisely so you can see the allowance you are carrying.
What competing calculators miss
Miss 1: the reverse question. Most board foot tools only go one way, from dimensions to a total. The equally common yard question, how many boards do I buy to cover a required total, is left as mental arithmetic with a rounding error built in. Boards needed mode here rounds up properly and shows the overage you will actually receive.
Miss 2: a straight answer on nominal versus actual. Competitor guidance contradicts itself: some pages insist actual dimensions should always be used, others bill nominal without explaining why, and at least one worked example uses actual dimensions in its own arithmetic while telling readers to use nominal. The billing rule depends on the stock, and this page states it plainly with the size table to back it up.
Miss 3: waste priced honestly. Tools that apply a price to the net total understate the invoice, because you pay for the waste allowance too. Here the cost line is calculated on the with-waste figure, and both figures stay visible so the allowance is a decision, not a surprise.
Frequently Asked Questions
A unit of lumber volume equal to 144 cubic inches: a board 1 inch thick, 12 inches wide and 12 inches long. Any shape with the same volume holds the same board feet, which is why a 2×6 and a 1×12 of the same length both work out to 1 board foot per linear foot.
Multiply thickness in inches by width in inches by length in feet, then divide by 12. If the length is in inches, divide by 144 instead. For ten 2×6 boards at 8 feet: (2 x 6 x 8) / 12 = 8 board feet per piece, times 10 pieces = 80 board feet.
Match the billing. Framing lumber is invoiced on nominal size, so use nominal figures (2 and 6 for a 2×6) when ordering or comparing quotes for dimension lumber. Rough and hardwood stock is invoiced on measured size, so measure and use actual figures. For layout and fit, always use actual dimensions.
On the nominal basis yards bill, (2 x 4 x 8) / 12 = 5.33 board feet. On measured size (1.5 x 3.5 inches) it is 3.50 board feet. The 5.33 figure is the one on your invoice for standard framing lumber.
Start at 10% for straight framing and simple work. Use 15 to 20% for angled work like decks and fences, and 20 to 25% or more for hardwood projects where you cut around defects and select for grain. The calculator keeps the net total and the with-waste order quantity separate so you can see the allowance.
Because you pay for what you order, not for what ends up in the finished project. Pricing the net total understates the invoice by exactly the waste percentage. Here the estimated cost is the with-waste board feet times your price per board foot: 88.00 x $2.50 = $220.00 in the worked example.
It reverses the calculation. Enter the board feet a project requires and the board feet in one board, and it returns the whole number of boards to buy, rounded up, plus what those boards actually supply. Needing 100 board feet in 8-board-foot boards returns 13 boards supplying 104 board feet.
No. A linear foot is length only and ignores thickness and width. A board foot is volume. They coincide for a 2×6 or a 1×12 (1 board foot per linear foot) and diverge for everything else, which is why this calculator reports board feet per linear foot for your exact size.
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References
- US Department of Agriculture, Forest Products Laboratory, “Wood Handbook: Wood as an Engineering Material” (General Technical Report FPL-GTR-190) – properties, moisture and dimension conventions for lumber. USDA Forest Products Laboratory: Wood Handbook (PDF). Accessed October 2026.
- National Institute of Standards and Technology, Voluntary Product Standard PS 20, the American Softwood Lumber Standard – defines nominal and dressed (actual) sizes for softwood lumber, the basis of the size table in this article. National Institute of Standards and Technology. Accessed October 2026.
- American Lumber Standard Committee – administers the softwood lumber standard and the grading system US yards bill against. American Lumber Standard Committee. Accessed October 2026.
- American Wood Council – design values, span guidance and lumber resources for wood construction. American Wood Council. Accessed October 2026.
- Western Wood Products Association – western lumber grading, sizing and use guidance. Western Wood Products Association. Accessed October 2026.