Board Foot Calculator
Enter the nominal thickness, width and length of a piece of lumber — we calculate the board feet per piece, the total board feet for the order, and the cost at your lumber yard price.
Total board feet
12
- Board feet per piece
- 12
- Cubic inches (total)
- 1,728
Board feet = (thickness × width × length in inches) ÷ 144, or equivalently (thickness × width × length in feet) ÷ 12. Always use the nominal lumber dimensions — that is what the lumber yard and the published price-per-BF refer to (NHLA Rules Book; USDA Forest Products Laboratory FPL-GTR-282).
How to use this calculator
Enter the lumber as the lumber yard quotes it — by NOMINAL dimensions. A "2 by 6 by 12 footer" is thickness 2, width 6, length 12, even though the dressed S4S piece you take home measures roughly 1.5" × 5.5". The board-foot count and the yard price both refer to the nominal size; using the actual dressed dimensions would under-count the volume by about 30% and you would underpay (and probably get short-shipped). Quantity is the number of identical pieces in the order. Price per board foot is optional — leave it at zero if you just want the BF number.
How the calculation works
A board foot is 144 cubic inches — a 12-inch × 12-inch × 1-inch slab. The formula is BF per piece = (thickness in × width in × length in) ÷ 144, which simplifies to (thickness × width × length-in-feet) ÷ 12 because there are 12 inches in a foot. Multiply by the quantity for the total BF on the order, then by the price-per-BF for the total cost. The formula and the nominal-dimension convention are set out in the National Hardwood Lumber Association Rules Book and the USDA Forest Products Laboratory technical report FPL-GTR-282.
Worked example
Twenty 2 × 6 × 12 ft pressure-treated boards for a deck frame, quoted at $4.50 per board foot. BF per piece = (2 × 6 × 12) ÷ 12 = 12 BF. Order total = 20 × 12 = 240 BF, which is 240 × 144 = 34,560 cubic inches of nominal wood. At $4.50/BF the lumber subtotal is 240 × 4.50 = $1,080 before tax and delivery. Sanity-check against a published yard ticket: Home Depot routinely quotes a single 2×6×12 at the BF-equivalent of 12 BF, so the math lines up with the receipt.
Frequently asked questions
What is a board foot?
A board foot, abbreviated BF or FBM ("foot board measure"), is the standard volume unit for sawn lumber in the US and Canadian timber trade. One board foot is 144 cubic inches — a piece 12 inches square and 1 inch thick. Lumber yards quote prices per BF for hardwoods and for any oversize stock that does not fit a tidy "per piece" price; understanding the unit is the only way to compare prices across thicknesses and lengths fairly.
Why does the calculator use nominal sizes instead of the actual dressed dimensions?
Because that is how the lumber industry sells, prices, and quotes timber. A "2 × 4" stud is named for the rough green dimensions before it is planed; the dressed S4S piece in the yard is actually about 1.5" × 3.5", but every price list, mill order, and contractor estimate still treats it as a 2 × 4 for the BF count. Using the actual dressed numbers would under-count the volume by roughly 30% on softwoods and you would end up disputing the invoice. Hardwoods sold rough (R/L, random width and length) are an exception — those are measured by actual dimensions, BF is calculated on what you bought, not on a nominal call-out.
How is board foot different from linear foot?
A linear foot is a length measurement — it counts only how long a piece is, regardless of thickness or width. A 2 × 4 × 8 ft is 8 linear feet but 5.33 board feet. A 2 × 12 × 8 ft is also 8 linear feet but 16 board feet because the cross-section is three times bigger. Linear feet is used for trim, mouldings, and any piece sold in a single fixed cross-section; board feet is used when the price depends on cross-section, which is most dimensional lumber and almost all hardwood.
How do I convert board feet to cubic metres?
One board foot is exactly 0.002359737 cubic metres (144 cubic inches × 16.387 cm³/in³ ÷ 1,000,000). So 1,000 BF — the "MBF" unit used in wholesale timber pricing — is about 2.36 m³. UK and European lumber is sold by the cubic metre rather than by BF, so a quote of "£600 per m³" for European oak is roughly equivalent to ($/USD per BF) × 0.71 (using 1 USD ≈ £0.83 and 1 m³ ≈ 424 BF).
Does the calculator account for kerf, defects, or waste?
No — it gives the geometric board-foot count for the nominal dimensions, which is what you order and what the yard charges. Add a separate wastage allowance for your project: 10% is the rule-of-thumb for square cuts in framing, 15% for trim and finished carpentry, and 20–30% for hardwood furniture work where you are cutting around knots and defects in random-width stock. Order the BF figure from the calculator multiplied by (1 + wastage).
Can I use this for plywood or sheet goods?
Not directly. Plywood, OSB, MDF, and other sheet goods are sold by the sheet (typically 4 ft × 8 ft) or by the square foot of face area, not by board feet. If a supplier does quote BF for a sheet — which is unusual — they will use the actual thickness (3/4", 1/2", etc.) and the full 32 ft² face area, so the math is BF = thickness × 32. For pricing comparisons across stock types, square footage or cost per sheet is the more useful number.