Board Foot Calculator
Enter nominal thickness, width, length and piece count to get board feet, total volume and cost — using the nominal-dimension convention hardwood is bought and sold by.
Last updated: 2026-09-22
How the calculation works
- One board foot is 144 cubic inches of nominal lumber — a 1 in thick × 12 in wide × 1 ft long board.
- Thickness enters in quarter-inches (the 4/4, 5/4, 6/4 hardwood convention), width in inches, length in feet — the three numbers every hardwood quote uses.
- Totals multiply by piece count; cost multiplies by your price per BF.
- The formula uses nominal dimensions: a 2×4 is 2 in × 4 in for BF purposes even though it dresses to 1.5 × 3.5.
Formula
BF = thickness_in × width_in × length_ft / 12 (per piece) total BF = BF × pieces cost = total BF × price
| Symbol | Meaning | Unit |
|---|---|---|
BF | Board feet — 144 in³ of nominal lumber | BF |
4/4 | Quarter-inch thickness convention (4/4 = 1 in) | — |
nominal | Rough-sawn dimensions before milling | in |
Worked example
Interpreting the result
Hardwood lumber is sold by the board foot at random widths, so your actual order's BF depends on the boards you pick — the calculation here is an estimate for budgeting: measure or average the stock you'd actually select. Construction softwood (2×4, 2×8) is sold by the piece, so BF applies only when comparing dimensional lumber prices or ordering rough timber. Milled thickness is below nominal — 4/4 hardwood finishes at 13/16 in after surfacing — which is why the nominal convention persists for pricing.
Assumptions
- Nominal (rough) dimensions throughout — the pricing standard for hardwood.
- Random-width lumber averaged; a fixed-width order uses that width.
- Price per BF excludes delivery, milling and waste from defects.
Limitations
- Actual usable yield is lower — defects, end checks and cut-offs typically consume 20–30% of rough BF.
- Not valid for sheet goods (plywood sold by the 4×8 sheet) or dimensional softwood (sold by the piece).
- Some yards quote 'Super BF' or surface-measure variants — check local convention.
Board feet vs the wood you actually get
You pay for nominal board feet but build with less. Three deductions stack between the quote and the finished part: manufacturing defects (knots, splits, warp — graded stock limits but doesn't eliminate them), planing (4/4 rough becomes 13/16 finished), and cut-off waste when parts are laid out on boards of random width. Furniture makers budget 1.3–1.5× the finished part volume in rough BF. The number this calculator produces is the purchasing figure — what you order at the yard — not the yield, and confusing the two is how projects run out of material at 80% completion.
Frequently asked questions
How do I calculate board feet?
Thickness (in) × width (in) × length (ft) ÷ 12. A 2 in thick × 6 in wide × 10 ft board is 2 × 6 × 10 / 12 = 10 BF. Multiply by piece count for an order.
What does 4/4 mean in lumber?
Four quarters of an inch — 1 in nominal thickness. Hardwood thickness is always quoted in quarters: 5/4 = 1.25 in, 6/4 = 1.5 in, 8/4 = 2 in. After milling, 4/4 finishes around 13/16 in.
Why is a 2×4 not 2 inches by 4 inches?
The nominal size is the rough-sawn green dimension; planing and drying shrink it to 1.5 × 3.5 in. Board foot pricing uses the nominal figure — a convention that persists because rough lumber is what sawmills sell by volume.