Use this mode for one board of a known nominal size and length. Pick a standard nominal cross-section (1×4, 2×4, 4×4 …) or enter custom thickness and width in inches.
BF = (T × W × L_ft) / 12
Use this mode when you're buying N identical boards — for example, 12 pieces of 2×4 × 8 ft for a deck frame. The calculator multiplies the single-piece BF by the count.
Total BF = N × (T × W × L_ft) / 12
Use this mode when your order mixes different sizes — for example, 6 × 2×4 × 8 ft plus 4 × 2×6 × 10 ft plus 2 × 1×12 × 8 ft. Add a row per size; the calculator sums the BF across all rows.
Total BF = Σ (Tᵢ × Wᵢ × Lᵢ × Nᵢ) / 12
A board foot (BF) is the standard volume unit lumber is sold in: 1 BF = 144 cubic inches, the volume of a board 1 inch thick × 12 inches wide × 12 inches long (or any equivalent volume). To compute board feet for a piece of lumber, multiply nominal thickness (inches) × nominal width (inches) × length (feet) and divide by 12. Lumberyards and hardwood dealers use NOMINAL dimensions for pricing — the label size, not the planed actual size — so a 2 × 4 × 8 ft is always 5.333 BF for billing, even though the planed dimensions are 1.5″ × 3.5″. This calculator handles a single piece, N identical pieces, and mixed orders, and can multiply the total by a price-per-board-foot to estimate cost.
A carpenter is buying 10 pieces of 2 × 4 nominal lumber, each 8 feet long, at $1.25 per board foot. How many board feet total, and what is the cost?
When you take the lumber home and measure it, a 2 × 4 is 1.5″ × 3.5″ — but the lumberyard still bills 5.333 BF per 8-foot piece because BF math is conventionally NOMINAL.
Board foot ≠ linear foot ≠ square foot. A board foot is a volume (144 cubic inches). A linear foot (sometimes 'lineal foot') is a length — 1 ft of any cross-section. A square foot is an area. Lumberyards quote softwood dimensional lumber by the piece or by the linear foot, but hardwood and rough-cut softwood are priced by the board foot because cross-section varies. Always confirm with the dealer which unit you're being quoted in. NOMINAL vs ACTUAL is the other classic gotcha: a 2 × 4 is sold as 2 × 4 but planed to 1.5″ × 3.5″; the BF math uses nominal dimensions, but the assembly clearance you actually have to work with is the actual size. This calculator computes BF using nominal dimensions because that is the dealer billing convention.
A board foot (BF) is the standard volume unit for lumber — specifically 144 cubic inches, or the volume of a board 1 inch thick × 12 inches wide × 12 inches long. Equivalent volumes are also 1 BF: a 2 × 6 × 12″ board, a 2 × 4 × 18″ board, and so on. Hardwood and rough-cut lumber are priced per BF; the formula is BF = (thickness_in × width_in × length_ft) / 12.
Nominal dimensions are the size on the label (2 × 4, 2 × 6, 4 × 4) — what the rough-sawn lumber measured before planing. Actual dimensions are what you measure with a tape after the lumber is dressed (planed) and dried. The standard subtraction: 1″ nominal → 0.75″ actual, 2″ nominal → 1.5″ actual, 4″ nominal → 3.5″ actual. Widths drop by 0.5″ for widths ≤ 6″ and 0.75″ for widths 8″ and up. For example, a 2 × 4 is actually 1.5″ × 3.5″ and a 2 × 10 is actually 1.5″ × 9.25″.
Compute total BF for your order, then multiply by the price per BF. For example, 50 BF of red oak at $6.75 / BF costs 50 × 6.75 = $337.50. The board-feet calculator above accepts an optional price input and shows total cost alongside the BF total. Compare prices on a per-BF basis — a high per-piece price on a wide board can still be cheaper per BF than narrow stock.
5.333 board feet. BF = (T × W × L_ft) / 12 = (2 × 4 × 8) / 12 = 64 / 12 = 5.333. Equivalent in cubic inches: 2 × 4 × 96 = 768 in³, and 768 / 144 = 5.333 BF. The lumberyard prices the 8-foot 2 × 4 as 5.333 BF even though the planed actual size is 1.5″ × 3.5″ — board-feet pricing is NOMINAL.
The 2 × 4 label is the rough-sawn dimension before the lumber is planed (dressed) on all four sides and kiln-dried to moisture content. Planing removes about ¼ inch from each face on lumber 6″ wide or less, and about ⅜ inch on lumber 8″ wide or more, which is why a 2 × 4 finishes at 1.5″ × 3.5″ but a 2 × 10 finishes at 1.5″ × 9.25″. The American Lumber Standards Committee (ALSC) standardized these reductions in PS 20 — that's why every dealer's 2 × 4 measures the same actual size.
Linear feet and lineal feet are the same thing — both mean length in feet, ignoring the cross-section. Board feet are a VOLUME unit (144 cubic inches). A 2 × 6 board that is 10 feet long is 10 linear feet (and 10 lineal feet), but only 10 BOARD feet by coincidence because (2 × 6 × 10) / 12 = 10. For any other cross-section the numbers differ: a 1 × 4 × 10 ft is 10 linear feet but only 3.333 board feet, and a 4 × 4 × 10 ft is 10 linear feet but 13.333 board feet.
Same formula as dimensional lumber — BF = (T × W × L_ft) / 12 — but rough-cut lumber is measured at the size it was cut, before any drying or planing. A rough 5/4 board (1.25 inches thick) actually IS 1.25″ thick when you receive it; you'd enter T = 1.25 in this calculator. Sawmill operators often quote 4/4, 5/4, 6/4, 8/4 etc. — that's thickness in quarters of an inch (4/4 = 1″, 5/4 = 1.25″, 8/4 = 2″) at the rough size.
For hardwood projects, yes — order 10% to 20% more BF than your cut list calls for, because you'll lose material to checking (end-cracks), knots, sapwood you cut around, and rip cuts that don't yield clean grain. For dimensional softwood used in framing where you mostly cut to length without ripping, a 5–10% overage handles bad cut-offs and on-site mistakes. The mixed-order mode lets you add a row for the buffer.
Reference: American Lumber Standard Committee (ALSC) Voluntary Product Standard PS 20 — standard nominal-to-actual dimension reductions for U.S. dimensional softwood lumber. National Hardwood Lumber Association (NHLA) Rules Book for board-foot measurement of hardwood lumber.
Deck Frame
A typical deck frame uses a dozen pressure-treated 2 × 4 × 8 ft pieces for the rim joists and headers. At $1.25 / BF, what's the total order and cost?
Total = 64 BF, estimated cost = $80.00
Nominal 2 × 4 measures 1.5″ × 3.5″ after planing — but board-feet pricing uses the NOMINAL 2 × 4 dimensions.
Hardwood Tabletop
A solid red oak tabletop, 30 × 60 inches, finished to 0.75 in (sold as 4/4 = 1 in nominal). At $6.50 / BF retail, how much hardwood and what does it cost?
Tabletop ~12.5 BF; order 15 BF for waste; cost ≈ $97.50
Hardwood is sold in quarters: 4/4 = 1 in, 5/4 = 1.25 in, 6/4 = 1.5 in, 8/4 = 2 in. Enter the nominal (rough) thickness, not the finished thickness.
Mixed Workbench Order
A simple workbench project that combines three different lumber sizes. Use the mixed-order mode to sum the BF across all rows.
Total ≈ 43.1 BF; estimated cost ≈ $64.65
The mixed mode skips fully-empty rows silently but blocks the total when any row has a typo, so a stray non-numeric entry can't silently understate your order.
A board foot is a volume unit — specifically 144 cubic inches, the volume of a 1″ × 12″ × 12″ board. The pricing formula:
Where:
The American Lumber Standards Committee (ALSC) PS 20 standard defines how rough-sawn dimensions are planed and dried. Use nominal dimensions for board-foot pricing and project material lists; use actual dimensions when laying out the project and checking clearances.
| Nominal | Actual (in) | BF / ft of length |
|---|---|---|
| 1 × 2 | 0.75″ × 1.5″ | 0.16666667 |
| 1 × 4 | 0.75″ × 3.5″ | 0.33333333 |
| 1 × 6 | 0.75″ × 5.5″ | 0.5 |
| 1 × 8 | 0.75″ × 7.25″ | 0.66666667 |
| 2 × 4 | 1.5″ × 3.5″ | 0.66666667 |
| 2 × 6 | 1.5″ × 5.5″ | 1 |
| 2 × 8 | 1.5″ × 7.25″ | 1.3333333 |
| 2 × 10 | 1.5″ × 9.25″ | 1.6666667 |
| 2 × 12 | 1.5″ × 11.25″ | 2 |
| 4 × 4 | 3.5″ × 3.5″ | 1.3333333 |
| 4 × 6 | 3.5″ × 5.5″ | 2 |
BF / ft of length lets you size up an order without a calculator: multiply the per-foot figure by total linear feet to get total BF. For example, 100 linear feet of 2 × 6 = 100 × 1.0 = 100 BF.