Board Foot Calculator

How do you calculate board feet of lumber?

A board foot is a volume unit equal to 144 cubic inches, so the arithmetic is thickness in inches × width in inches × length in inches ÷ 144. A board 1 in thick, 12 in wide, and 12 in long is exactly one board foot. If the length is easier in feet, the equivalent form is thickness (in) × width (in) × length (ft) ÷ 12. The American Softwood Lumber Standard states the same rule in trade form: the number of board feet is obtained by multiplying nominal thickness in inches by nominal width in feet by length in feet [1]. Multiply the per-piece figure by the number of identical pieces, then total each size group separately. Never mix nominal and surfaced dimensions inside one tally.

Work size group by size group. A cut list of 10 pieces of 1×6 at 8 ft plus 6 pieces of 2×8 at 10 ft is two calculations, not one average: 40 BF plus 80 BF equals 120 board feet. Round only at the end and keep at least two decimals while you work, because 0.333 BF per lineal foot compounds quickly across a large order. Add a defect and planing allowance on top of the net tally — 15% to 30% is common for random-width, random-length rough hardwood, and more when you need long clear rips. This calculator returns net geometric volume; it does not deduct planing loss, cull defect, or saw kerf.

What is the difference between nominal and actual lumber dimensions?

Nominal size is the trade name — 1×6, 2×4, 2×10 — and actual (dressed) size is what you measure after the mill surfaces the piece. Under the American Softwood Lumber Standard, a nominal 1-inch board is dressed to 3/4 in (19 mm) dry, and nominal 2-inch dimension lumber is dressed to 1-1/2 in (38 mm). Widths shrink more: nominal 4 in becomes 3-1/2 in (89 mm), 6 in becomes 5-1/2 in (140 mm), 8 in becomes 7-1/4 in (184 mm), and 12 in becomes 11-1/4 in (286 mm) [1]. The standard is explicit that no inference should be drawn that nominal sizes are dressed sizes [1].

Board measure uses nominal dimensions, which is why a 2×4 that actually measures 1-1/2 × 3-1/2 in is still tallied as 2 × 4. Using actual dimensions would understate that 2×4 by about 34%: 1.5 × 3.5 = 5.25 in² of cross section against 8 in² nominal. Cubic measure is the exception — the standard specifies dressed sizes when lumber is measured in cubic meters [1]. Keep two habits separate: order and price by nominal board measure, and lay out joinery, rip widths, and clearances from the actual dressed dimensions you measure with a tape.

What does 4/4, 6/4, and 8/4 mean in lumber?

Quarter notation is hardwood shorthand for rough thickness in quarter-inches before surfacing. 4/4 (four-quarter) is 1 in, 5/4 is 1-1/4 in, 6/4 is 1-1/2 in, 8/4 is 2 in, 10/4 is 2-1/2 in, and 12/4 is 3 in. The numerator counts quarter-inches, so 8/4 = 8 × 1/4 = 2 in. Board-foot tallies use that quarter thickness, not the surfaced thickness: 20 square feet of 8/4 walnut is 40 board feet, because 2 in of nominal thickness doubles the one-inch base. That is also why 4/4 is the easy case — one square foot of surface equals exactly one board foot.

Surfaced-two-sides (S2S) hardwood arrives thinner than its quarter call. 4/4 is commonly supplied near 13/16 in and 8/4 near 1-3/4 in, though the exact surfaced thickness varies by mill and by the grading rules in force, so confirm it before planning a 3/4-in finished part. You still buy and pay for the full 4/4 or 8/4 thickness. If you need a finished 1-in component, order 5/4 or 6/4 and build the extra board feet into the budget. Enter the quarter thickness in this calculator — 1 for 4/4, 1.5 for 6/4, 2 for 8/4 — with the width and length you actually have.

How many board feet are in a 1x6 board 8 feet long?

One 1×6 at 8 ft is 4 board feet. Convert the length to inches (8 ft = 96 in), then compute (1 × 6 × 96) ÷ 144 = 576 ÷ 144 = 4.00 BF. Ten identical pieces are 40 board feet — the named result for a typical shelving or fencing order. The shortcut form gives the same answer: 1 × 6 × 8 ÷ 12 = 4. Because a 1×6 delivers exactly 0.5 BF per lineal foot, a mixed pile of 1×6 tallies fast: total lineal feet ÷ 2. Eighty lineal feet of 1×6 is 40 board feet no matter how the lengths are cut.

Now price it. At a hypothetical $4.50 per board foot for kiln-dried hardwood, 40 BF is $180 before tax; at $7.25 per board foot it is $290. Those are arithmetic scenarios, not quotes. Add the waste allowance before ordering rather than after: 40 BF plus 20% for defect and planing is 48 BF, which is twelve 1×6 × 8 ft pieces instead of ten. If the supplier sells random-width rough stock, ask whether the tally is taken before or after surfacing, and whether short lengths are counted at full or reduced footage.

Is hardwood priced by the board foot or the linear foot?

Hardwood is normally priced by the board foot, softwood dimensional lumber by the piece or the linear foot, and sheet goods by the sheet. Those units are not interchangeable. A linear (lineal) foot counts only length; a board foot counts volume. One linear foot of 1×4 is 0.333 BF, one linear foot of 2×6 is 1.00 BF, and one linear foot of 2×10 is 1.667 BF — three very different amounts of wood for the same single foot of length. When a quote reads $3.20 per foot, find out whether that foot is lineal or board measure before you compare suppliers.

Two more conversions come up constantly. One cubic foot of solid lumber contains 12 board feet (1,728 in³ ÷ 144), so a 500-BF order is about 41.7 ft³ of wood. Log and standing-timber conversions are a different animal: USDA Forest Service planning documents have used roughly 6.0 board feet per cubic foot for log scaling, because saw kerf and slabbing waste are built into that ratio [2]. Use 12 BF per ft³ for finished lumber volume and never mix the two. Plywood, MDF, and other panels stay on a per-sheet basis; this calculator is for solid lumber.

How many board feet are in common lumber sizes?

Board measure uses nominal thickness and width. Multiply by quantity and add a separate waste allowance.

What are the actual dimensions of nominal lumber sizes?

Dressed sizes from the American Softwood Lumber Standard. The standard states that nominal sizes are not dressed sizes.

What do hardwood quarter thicknesses mean in board feet?

Tally and pricing use the quarter thickness, not the surfaced thickness. Confirm surfaced dimensions with your supplier.

What to do with this result

• price lumber per board footMaterial Cost Calculator

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