Board Feet / Lumber Calculator — ft, in to board feet, cost
How to use this calculator
Enter lumber dimensions — thickness, width, and length — to calculate board feet. Use Single Piece for one board, Multiple Pieces for a cut list of different sizes, or Common Lumber for nominal sizes (2x4, 2x6…) with actual dressed dimensions applied automatically. Board feet is the bill-of-material unit your yard and quote use.
Formula: Board Feet = Thickness (in) x Width (in) x Length (ft) / 12. One board foot equals a 1" x 12" x 1' piece of lumber. Nominal sizes use actual dimensions (e.g., 2x4 = 1.5" x 3.5").
Saved Calculations
| Time | Mode | Size | Length | Qty | BF | Cost |
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How to Calculate Board Feet
A board foot is the lumber-yard unit for hardwood and rough-sawn stock: a piece 1 in thick × 12 in wide × 1 ft long, or 144 cubic inches. Charged thickness is normally the rough/quarter size (4/4 = 1″, 5/4 = 1¼″, 8/4 = 2″), not the surfaced size, so price your stock at the thickness the mill bills. Build a takeoff in Multiple Pieces mode, then add 10–15% for cutting and defect waste before ordering.
Formula
BF = T(in) × W(in) × L(ft) ÷ 12. Equivalently BF = T × W × L(in) ÷ 144. For surfaced framing the calculator applies actual sizes — a nominal 2×4 is 1.5″ × 3.5″, a 2×6 is 1.5″ × 5.5″, a 2×8 is 1.5″ × 7.25″ — so volume and weight reflect what is delivered, not the call-out size.
Nominal vs Actual & Field Use
Dimensional softwood is sized per the IRC/NDS dressed-lumber schedule after kiln drying and planing. Use board feet for hardwood and pricing comparisons; use piece counts when framing. For a deck or floor frame, size members with the floor joist span calculator and the deck calculator, then total the lumber bill here. For walls use the stud wall calculator, for fencing the fence calculator, and for sheet goods the plywood & OSB calculator.
Weight Estimation
Weight is estimated at about 35 lb/ft³, typical for kiln-dried softwood (SPF, Douglas Fir, ~12% MC). Green lumber is heavier; hardwoods like oak or maple run 40–50 lb/ft³, while cedar and redwood are lighter at 22–28 lb/ft³.
FAQ
Do I use nominal or actual size? For surfaced framing the actual size governs volume — this tool applies it automatically in Common Lumber mode. For rough hardwood, enter the billed thickness (4/4, 8/4).
How much waste should I add? 10–15% for framing cuts and defects, ~10% for sheathing.
Why does my receipt differ? Mills round up to the next 1/4 BF and price by the rough quarter size, not the surfaced dimension.
At the lumber yard
2025 USA pricing (big-box, per piece): 2x4x8 SPF stud $3.50–5, 2x4x10 $5–7, 2x6x8 $7–10, 2x10x12 $20–28, 5/4x6x12 PT decking $14–22, 4x4x8 PT post $14–22, 6x6x8 PT $42–60. Per board foot: SPF construction $0.60–1.10/BF, #1 SYP PT $1.20–2.20/BF, #1 common red oak $5–8/BF, walnut $12–20/BF. The number-one estimator mistake is buying by piece count and forgetting the 10–15% cutoff allowance — a 16 ft wall with 92⅝″ studs at 16″ o.c. needs more studs than the simple math says once you add corners, T-intersections, headers and the second top plate, per IRC §R602.3. For posts and beams, also verify your size with the floor joist span calculator before ordering — bumping a 2x10 to a 2x12 adds 20% volume but often saves on doubling.
