Board foot calculator for lumber and hardwood

Buying 2×4s or pine boards by the piece at a home center? Use the cut list calculator instead.

Enter the size the lumber is sold by: nominal size for construction lumber (a 2×4 is 2 × 4), rough thickness for hardwood (type 4/4, 5/4 or 8/4 straight into the field). Price it per board foot, per piece, per MBF or per linear foot — whichever the yard quotes — and the calculator converts to the others. New to this? Words explained.

How to calculate board feet

Board feet measure volume, not length. Multiply thickness by width by length and divide by the volume of one board foot. With everything in inches, divide by 144; with the length in feet, divide by 12.

board feet = thickness (in) × width (in) × length (in) ÷ 144
board feet = thickness (in) × width (in) × length (ft) ÷ 12
1 board foot = 144 cu in ≈ 0.00236 m³  ·  1 m³ ≈ 423.8 board feet

Example: a 2×6 that is 10 ft long is 2 × 6 × 10 ÷ 12 = 10 board feet. A stack of twelve of them is 120 board feet. The board foot chart lists every common size from 1×4 to 6×6 at 8 to 20 ft.

Worked examples

• How many board feet in a 2x4x8 — the stud everyone prices, and how to turn an MBF quote into a per-piece price.
• How many board feet in a 2x6x8 — the size where board feet equal linear feet.
• How many board feet in a 4x4x8 — posts, and why the wet ones measure fat.
• Board feet in a 4/4 hardwood board, 8 in × 8 ft — how a hardwood dealer tallies a single board.
• Board feet in an 8/4 slab, 24 in × 8 ft — measuring a live edge that is not the same width twice.

Nominal size or actual size?

Use the size the lumber is sold by, because that is what the yard multiplies by the price:

• Softwood dimensional lumber (2×4, 2×6, 4×4, 1×6) is tallied on its nominal size — the rounded name, not the tape measure. A 2×4 is dressed to 1½ × 3½ in under the American Softwood Lumber Standard (NIST PS 20), but a 2×4×8 still counts as 5.33 board feet.
• Hardwood is sold by the quarter-inch thickness it was sawn at: 4/4 (four quarters, 1 in), 5/4 (1¼ in), 6/4, 8/4 (2 in). The tally usually stays on that rough thickness even if the dealer surfaces it for you, while width and length are measured on each board.
• True volume — for weight or shipping — needs actual dimensions. The lumber dimensions calculator shows both for common sizes.

Boards under 1 in thick

Yards do not bill thin stock by its true volume. Under the National Hardwood Lumber Association (NHLA) rules, hardwood thinner than 1 in is counted as if it were 1 in — board feet equal its surface measure — so a 3/4 in board 6 in wide and 8 ft long is 4 board feet, not the 3 its wood actually fills. Softwood 1× boards come out the same way because they are billed on their nominal 1 in thickness. The calculator uses this yard tally by default; switch to True volume under More options when you want the wood that is actually there, for weight or a finish estimate.

Tips for buying by the board foot

• Add waste. Rough hardwood loses thickness to planing and length to checked ends and defects; 15–30% extra is a common planning range, more for figured or low-grade boards.
• Random-width hardwood is tallied board by board. Under the NHLA rules, as illustrated in the American Hardwood Export Council grading guide, each board’s surface measure is rounded to a whole number and lengths drop to the whole foot, so your receipt may not match your own math exactly. The hardwood tally calculator runs a stack of boards the way the yard does.
• Compare prices across units. If one store sells by the piece and another by the board foot, convert both to board feet (or use the board feet to linear feet calculator). Per-piece and per-linear-foot prices here are charged on whole boards, so waste rounds up to the next board.
• Fractions work in the fields: type 5/4, 1 1/2 or 3/4, or a length like 8' 6".