Calculators · Board Foot Calculator
Lumber & framingBoard Foot Calculator
Add your boards by thickness, width, length and quantity to get the total board feet, cubic feet and your cost.
Total board feet
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How to calculate board feet
A board foot is a unit of volume for lumber. It is a piece of wood 12 inches wide, 12 inches long and 1 inch thick, which is 144 cubic inches (University of Wisconsin-Madison Extension, checked October 2026). The American Hardwood Export Council calls the board foot the unit of measurement for hardwood lumber and gives the same formula (AHEC).
- One board. Thickness in inches × width in inches × length in feet ÷ 12.
- If the length is in inches. Thickness × width × length in inches ÷ 144. It is the same number.
- Several boards of the same size. Multiply the board feet of one board by the quantity.
- Different sizes. Work out each size on its own line and add the lines. That is what the calculator does.
Board feet convert to ordinary volume with one number. 12 board feet make 1 cubic foot, so cubic feet are board feet ÷ 12, cubic inches are board feet × 144, and cubic meters are cubic feet × 0.0283168 (one cubic foot is 0.3048 m cubed). The calculator shows all three under the total.
Example: a mixed lumber order
Say you need six 2×4 studs that are 8 ft long, four 5/4 × 6 hardwood boards that are 8 ft long, and two 8/4 × 8 boards that are 10 ft long. Type the thickness as 2, 5/4 and 8/4, or choose the quarters unit.
| Line | Operation | Board feet |
|---|---|---|
| 6 × 2×4×8 | 6 × (2 × 4 × 8 ÷ 12) | 32.00 |
| 4 × 5/4×6×8 | 4 × (1.25 × 6 × 8 ÷ 12) | 20.00 |
| 2 × 8/4×8×10 | 2 × (2 × 8 × 10 ÷ 12) | 26.67 |
| Total | 32 + 20 + 26.67 | 78.67 |
That is 78.67 ÷ 12 = 6.56 cubic feet, 11,328 cubic inches or 0.186 cubic meters. If you add 10% for waste, you buy 78.67 × 1.10 = 86.53 board feet. Multiply that by the price on your quote to get the cost.
Board feet in common boards
These use the nominal size, which is how lumber is named, and the usual lengths.
| Nominal size | 8 ft | 10 ft | 12 ft |
|---|---|---|---|
| 1×6 | 4.00 | 5.00 | 6.00 |
| 1×12 | 8.00 | 10.00 | 12.00 |
| 2×4 | 5.33 | 6.67 | 8.00 |
| 2×6 | 8.00 | 10.00 | 12.00 |
| 2×8 | 10.67 | 13.33 | 16.00 |
| 2×10 | 13.33 | 16.67 | 20.00 |
| 2×12 | 16.00 | 20.00 | 24.00 |
| 4×4 | 10.67 | 13.33 | 16.00 |
Nominal and actual size
A 2×4 is not 2 inches by 4 inches. The University of Wisconsin-Madison fact sheet says that today’s surfaced lumber is not exactly 2 inches thick or 6 inches wide, so the formula with nominal sizes gives the nominal volume and not the true one. It works out the real volume of a 10 ft 2×6 as 6.875 board feet, against 10 for the nominal size. For softwood, the federal rule that defines the board foot for the softwood lumber promotion program bases the calculation on the nominal thickness and width and the actual length (7 CFR 1217.4).
The real sizes come from the American Softwood Lumber Standard, PS 20-25 (January 2025, table 3, checked October 2026). These are the minimum dressed sizes of dry lumber. The standard says the thicknesses apply to all widths and the widths apply to all thicknesses. The last two columns compare an 8 ft piece.
| Nominal | Actual size, dry (in) | Nominal, 8 ft | Actual, 8 ft |
|---|---|---|---|
| 1×4 | 3/4 × 3-1/2 | 2.67 bf | 1.75 bf |
| 1×6 | 3/4 × 5-1/2 | 4.00 bf | 2.75 bf |
| 1×8 | 3/4 × 7-1/4 | 5.33 bf | 3.63 bf |
| 1×12 | 3/4 × 11-1/4 | 8.00 bf | 5.63 bf |
| 2×4 | 1-1/2 × 3-1/2 | 5.33 bf | 3.50 bf |
| 2×6 | 1-1/2 × 5-1/2 | 8.00 bf | 5.50 bf |
| 2×8 | 1-1/2 × 7-1/4 | 10.67 bf | 7.25 bf |
| 2×10 | 1-1/2 × 9-1/4 | 13.33 bf | 9.25 bf |
| 2×12 | 1-1/2 × 11-1/4 | 16.00 bf | 11.25 bf |
| 4×4 | 3-1/2 × 3-1/2 | 10.67 bf | 8.17 bf |
To buy lumber the way a yard sells it, use the nominal size. To know how much wood is really in the piece, use the actual size. The quick pick in the calculator fills in the nominal size and, under the result, shows the board feet with the actual size next to it. Green lumber and some pieces come out a little bigger than these minimums.
Hardwood thickness in quarters
Hardwood is named by thickness in quarters of an inch. 4/4 (“four-quarter”) is 1 inch. The American Hardwood Export Council says the standard thicknesses are expressed this way for rough sawn lumber (AHEC, Measurement, checked October 2026). It also says that when the lumber is surfaced, the finished thickness is the nominal thickness minus 3/16 inch for lumber of 1-1/2 inches or less and minus 1/4 inch for lumber of 1-3/4 inches or more. The last column applies that rule.
| Name | Rough thickness (in) | Rough (mm) | Surfaced by AHEC rule (in) |
|---|---|---|---|
| 3/4 | 3/4 | 19.0 | 9/16 |
| 4/4 | 1 | 25.4 | 13/16 |
| 5/4 | 1-1/4 | 31.8 | 1-1/16 |
| 6/4 | 1-1/2 | 38.1 | 1-5/16 |
| 8/4 | 2 | 50.8 | 1-3/4 |
| 10/4 | 2-1/2 | 63.5 | 2-1/4 |
| 12/4 | 3 | 76.2 | 2-3/4 |
| 16/4 | 4 | 101.6 | 3-3/4 |
The board foot formula uses the thickness in inches, so a 5/4 board counts as 1.25. Type 5/4 in the thickness box, or pick the “quarters” unit and type 5. If your supplier bills a surfaced board on its finished thickness instead of its rough thickness, type that thickness.
Waste, price and cost
- Waste. The box starts empty and no percentage is assumed. If you type one, the calculator adds it to the total and shows the board feet to buy.
- Price. No price is shown on this page, because lumber prices change by species, grade and region. Type the price per board foot from your quote and the calculator multiplies it by the board feet to buy.
- Units. Thickness can be inches, quarters, millimeters or centimeters. Width can be inches, feet, millimeters or centimeters. Length can be feet, inches, yards or meters, or something like 8'6" or 8 ft 6 in.
Frequently asked questions
How do I calculate a board foot?
Multiply the thickness in inches by the width in inches by the length in feet, then divide by 12. A board foot is a piece 1 inch thick, 12 inches wide and 12 inches long, which is 144 cubic inches. If your length is in inches, divide by 144 instead. A 2 inch by 6 inch board that is 8 feet long is 2 × 6 × 8 ÷ 12 = 8 board feet.
How many board feet is a 2x4x8?
A 2x4 that is 8 feet long is 5.33 board feet (5 1/3), because 2 × 4 × 8 ÷ 12 = 5.3333. That uses the nominal size, which is how lumber is named and sold. The real volume is smaller. A dry 2x4 measures 1-1/2 by 3-1/2 inches, and 1.5 × 3.5 × 8 ÷ 12 = 3.5 board feet.
How many board feet are in a 1x12x12?
A 1x12 that is 12 feet long is 12 board feet, because 1 × 12 × 12 ÷ 12 = 12. With the real dry size of 3/4 by 11-1/4 inches the same board is 0.75 × 11.25 × 12 ÷ 12 = 8.44 board feet.
How many board feet are in a 2x4x10?
A 2x4 that is 10 feet long is 6.67 board feet (6 2/3), because 2 × 4 × 10 ÷ 12 = 6.6667. With the real dry size of 1-1/2 by 3-1/2 inches it is 1.5 × 3.5 × 10 ÷ 12 = 4.38 board feet.
Do board feet use nominal or actual sizes?
Nominal for softwood lumber. A University of Wisconsin-Madison Extension fact sheet says the formula gives the nominal volume when you use sizes like 2x6, and that using the real size gives the true volume. A federal regulation that defines the board foot for softwood says the calculation uses nominal thickness and width and the actual length. This calculator multiplies what you type, so type nominal sizes to match a lumber yard and real sizes to get the true volume.
What does 4/4 or 8/4 mean on hardwood?
It is the thickness in quarters of an inch. 4/4 is 1 inch, 5/4 is 1-1/4 inches, 6/4 is 1-1/2 inches and 8/4 is 2 inches. The American Hardwood Export Council says these names describe rough sawn thickness. Type 5/4 as the thickness, or pick “quarters” as the unit and type 5, and the calculator reads it as 1.25 inches.
How many board feet are in a cubic foot?
Twelve. A board foot is 144 cubic inches and a cubic foot is 1,728 cubic inches. In metric, one board foot is about 0.00236 cubic meters. The calculator shows the cubic feet, cubic inches and cubic meters of your total.
How do I find the cost of lumber in board feet?
Multiply the board feet you will buy by the price per board foot your supplier quotes. If you add a waste percentage, the calculator multiplies the price by the board feet with waste included. It does not suggest any price. Prices change by species, grade and region, so you type the one from your quote.
Building a deck with these boards? The deck calculator counts deck boards, joists and screws and has its own table of real board widths.
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