About Board Feet
Hardwood isn't sold by the piece — walnut, maple, and oak are priced per board foot, a volume measure that lets a dealer price random widths and lengths on one scale. Misfigure it and a furniture project's lumber bill surprises you at the register; figure it right and you can compare dealers and species on equal footing.
Enter the board's three dimensions, how many pieces, and optionally the dealer's per-board-foot price. You get total board feet, the per-piece figure, cubic inches, and cost. For a cut list with mixed sizes, run each size and add the results.
Pricing a floor rather than project lumber? Coverage math lives in the Flooring Calculator.
The Board-Foot Formula
One line, with the length conveniently in feet:
Board feet = thickness (in) × width (in) × length (ft) ÷ 12 1 board foot = 144 cubic inches = a 12″ × 12″ × 1″ slab
Worked example: a rough 8/4 maple board 8″ wide and 10′ long is 2 × 8 × 10 ÷ 12 = 13.33 board feet — at $8/bf, $106.67. Ten 8-foot 2×4s (actual 1.5″ × 3.5″) total 35 board feet.
Nominal vs Actual & Common Pieces
Surfaced softwood is named by its rough size but measures smaller. Board feet below use ACTUAL dimensions for an 8-foot piece — every value computed by this calculator:
| Nominal | Actual (in) | Board feet (8′ piece) |
|---|---|---|
| 1×4 | 0.75 × 3.5 | 1.75 |
| 1×6 | 0.75 × 5.5 | 2.75 |
| 2×4 | 1.5 × 3.5 | 3.50 |
| 2×6 | 1.5 × 5.5 | 5.50 |
| 2×8 | 1.5 × 7.25 | 7.25 |
| 2×10 | 1.5 × 9.25 | 9.25 |
| 2×12 | 1.5 × 11.25 | 11.25 |
| 4×4 | 3.5 × 3.5 | 8.17 |
Convenient coincidence: an 8-foot 2×anything works out to its nominal width × 0.5 − small change — a 2×8×8 is 7.25 bf because the actual width is 7.25″.
The Quarter System (4/4, 8/4…)
Hardwood thickness is quoted in quarters of an inch of ROUGH thickness: 4/4 (“four-quarter”) is 1″ rough, 5/4 is 1.25″, 6/4 is 1.5″, 8/4 is 2″, 12/4 is 3″. Dealers charge board feet on that rough thickness even after the board is surfaced down — S2S 4/4 stock actually measures around 13/16″, but you pay for the full 4/4. That's the convention, not a scam; the surfacing waste was real wood.
Practical buying notes: figure your project in finished dimensions, then buy the next quarter size up (a finished 1¾″ table leg needs 8/4 stock, not 6/4); add 15–30% for defects, grain matching, and test cuts — hardwood has knots and checks the grade allows; and confirm whether the dealer's tally is gross (before defect cutting) or net.