Board foot calculator, for any list of boards.

A board foot is a unit of lumber volume. To work out board feet, multiply the thickness in inches by the width in inches by the length in feet, then divide by 12. A board 1 inch thick, 6 inches wide and 8 feet long is 1 × 6 × 8 ÷ 12 = 4 board feet. This calculator does that for as many rows as you like, in inches, feet, millimetres or centimetres, and adds up the total, the cost and the cubic feet.

How to use the board foot calculator

1. Fill in the first row. Type the Pieces, then the Thickness, Width and Length. Each one has its own unit menu, so you can mix inches, millimetres and feet in one row.
2. Or pick a lumber size from "Size list", such as 2 x 4. It fills in the thickness and the width for you. "The size list fills in" on the right decides whether you get the nominal size or the actual dry size.
3. Press "Add a row" for the next board size. It starts as a copy of the row above, so change only what differs. Press the cross to remove a row.
4. Read "Total board feet". The working for each row is shown under the table.
5. Type "Extra for waste (%)" to see the total with extra. Type "Price per BF" to see the cost. Nothing is filled in for you.
6. Use "Copy result", "Print" or "Copy link" to keep the list. The link carries every row.

The formula and what it means

A board foot is 144 cubic inches of wood. The NIST Handbook 130 (2026 edition), section 2.12.1.1, checked 18 Oct 2026, defines it as the volume of a board 1 ft long, 1 ft wide and 1 in thick, or its equivalent. Twelve inches by twelve inches by one inch is 144 cubic inches, so a board foot is one twelfth of a cubic foot. That is why the formula divides by 12: it turns inches times inches times feet into board feet. One board foot is 0.002359737 cubic metres.

Worked examples

• A 1 × 6 board, 8 feet long. 1 × 6 × 8 ÷ 12 = 4 board feet. If your seller charges 8 a board foot, that is 4 × 8 = 32.
• A 2 × 4, 8 feet long, nominal. 2 × 4 × 8 ÷ 12 = 5.33 board feet.
• The same 2 × 4 at its actual dry size. 1.5 × 3.5 × 8 ÷ 12 = 3.5 board feet. The difference is why you should ask whether a price uses nominal or actual sizes.
• Ten of those 2 × 4s. 10 × 5.33 = 53.33 board feet, or 58.67 with 10% extra.
• Hardwood in quarters. 8/4 means 2 inches thick. 8/4 × 6 × 8 ÷ 12 = 8 board feet.
• Metric. A board 25 mm thick, 150 mm wide and 2.4 m long is 0.9843 in × 5.9055 in × 7.874 ft ÷ 12 = 3.81 board feet.
• A list. Ten 2 × 4 × 8 (53.33) plus four 1 × 6 × 10 (4 × 1 × 6 × 10 ÷ 12 = 20) is 73.33 board feet.

Nominal and actual sizes

Softwood lumber is named by its nominal size, like 2 x 4, but a dry 2 x 4 is cut smaller. NIST Handbook 130 (2026), Table 1, "Softwood Lumber Sizes", lists the minimum dressed sizes for dry lumber and quotes the US Department of Commerce standard PS 20-20 (checked 18 Oct 2026). Some of the rows the size list uses:

Hardwood is different. Its thickness is often given in quarters of an inch. Sellers differ on whether they bill by nominal or surfaced size, so ask which one they use.

Common problems

• Length in inches. The formula wants feet. The Length menu converts inches, yards, metres, centimetres and millimetres for you.
• Thickness in quarters. Pick "/4 (quarters)" and type 4 for 1 inch. Typing 4 with the unit on "in" would mean 4 inches.
• Fractions. Type 1 1/2 or 3 1/4. Feet and inches work in the Length box, for example 8'6".
• Waste. The page starts at 0. Add your own percent for cuts, knots and mistakes.

To change the result into other volume units, the unit converter has a Volume group. To add a waste percent on its own, use the percentage calculator. For other measuring jobs, the square footage calculator adds up areas.