Calculators/Board feet

Board foot calculator

Board feet from nominal dimensions, for one piece or a whole order — with an optional price per board foot when you are pricing a cut list.

The lumber

Use nominal sizes — a 2×4 counts as 2 by 4, not as its actual 1½ × 3½. That is how lumber is tallied and priced.

The tally

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Check the result against the job. This does the arithmetic from the values you enter. Building codes, span tables and material specifications vary by jurisdiction and by product, and the governing document is your approved drawings and your local code. Nothing you type here leaves your browser: the calculation runs on your device and we never receive it.

How this is checked. Every formula on this site runs from one shared calculation engine, and every one has a test fixture whose expected answer was worked out from the geometry or taken from a figure the trade already publishes — never from what the code returns. Some land exactly, which is the point: a 6/12 hip over a 144″ run is exactly 216″, a 45° crown in a square corner bevels at exactly 30°, and a 30° conduit bend has a multiplier of exactly 2. Where a number is a convention rather than arithmetic — a code limit, a waste allowance, bundles per square — it is an input with a stated default rather than a hidden constant. Found something wrong? Tell us at [email protected] and we will fix it and say so.

What a board foot is

One board foot is 144 cubic inches of lumber — a piece one inch thick, twelve inches wide and twelve inches long. Everything else is that same volume in a different shape.

Which gives the formula: thickness in inches × width in inches × length in feet, divided by 12. A 2×4×8 is (2 × 4 × 8) ÷ 12 = 5.33 board feet. A 1×12×12 is exactly 12 board feet, which is a useful one to remember as a sanity check.

Nominal, not actual

This is the part that catches people. A 2×4 does not measure 2 by 4 — it measures 1½ by 3½ after it has been surfaced and dried. But it is tallied and priced as a 2×4, so board feet use the nominal number.

Use actual dimensions instead and you will undercount by roughly a third, and your figure will not match the supplier's quote. The full table of what every size really measures is in the lumber dimensions reference.

Board feet against linear feet

Linear feet count length and ignore the cross-section, so 100 linear feet of 2×4 and 100 linear feet of 2×12 are the same number — while in board feet the 2×12 is three times the material. Dimensional lumber is usually sold by the piece or the linear foot; hardwood and rough stock are sold by the board foot. Know which one the quote in front of you is using.

Common questions

How do you calculate board feet?

Multiply nominal thickness in inches by nominal width in inches by length in feet, then divide by 12. A 2x4x8 is (2 × 4 × 8) ÷ 12, which is 5.33 board feet. One board foot is 144 cubic inches — a piece 1 inch thick, 12 inches wide and 12 inches long.

Do you use nominal or actual dimensions for board feet?

Nominal. A 2x4 is priced and tallied as 2 by 4 even though it actually measures 1 1/2 by 3 1/2 inches. Using actual dimensions would undercount every piece by roughly a third and put you badly out against a supplier quote.

What is the difference between board feet and linear feet?

Linear feet measure length alone and ignore the cross-section, so 100 linear feet of 2x4 and 100 linear feet of 2x12 are the same number. Board feet measure volume, so the 2x12 is three times the board footage. Dimensional lumber is often sold by the piece or the linear foot; hardwood and rough stock are usually sold by the board foot.

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