Board Foot Calculator — Lumber Volume and Quantity
Estimate the volume of dimensional lumber, rough-sawn boards, or hardwood sold by the board foot. Enter each board’s measured thickness and width in inches, its length in feet, the number of matching pieces, and any cutting or defect allowance.
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View all saved project estimatesWhat does the board foot calculator calculate?
One board foot equals 144 cubic inches. Multiply board thickness in inches by width in inches by length in feet, divide by 12, and multiply by the number of matching pieces. Add waste only for purchasing; the exact board-foot total remains the measured lumber volume.
Board-foot lumber volume formula
A one-foot length converts the entered cross-section into cubic inches, and division by 12 expresses that volume in 144-cubic-inch board feet. The piece count applies only to boards with identical dimensions. Waste increases the purchase target without changing the exact calculated volume.
How to measure for an accurate estimate
- Measure thickness and width at several points when rough lumber varies, then group boards with similar dimensions or calculate them separately.
- Enter length in feet; convert inches beyond a whole foot to a decimal, such as 8 feet 6 inches becoming 8.5 feet.
- Use the dimensions your seller applies to board-foot pricing, which may differ from the finished size after surfacing and drying.
- Separate mixed sizes into individual calculations and add their exact board-foot totals before applying one project-wide waste allowance.
Ten rough boards for a cabinet project
Ten matching boards measure 1 inch thick, 6 inches wide, and 8 feet long, with a 15% allowance for defects, milling, and cutting.
Each board contains 4 board feet; all ten contain 40 board feet, and the purchase target becomes 46 board feet after adding 15%.Before you purchase material
- Allow extra volume for knots, checks, sapwood exclusions, grain matching, milling loss, and cut optimization rather than relying on piece count alone.
- Ask whether the invoice rounds board dimensions or tallies every board individually; grading and measurement practices affect the final billed total.
- Buy boards long and wide enough for the finished parts, then verify that defects do not fall inside critical joinery or visible faces.
- Keep the exact volume separate from waste so quotes from different lumberyards can be compared on the same measured quantity.
Common questions
What is one board foot of lumber?
A board foot is a volume equal to 144 cubic inches, commonly pictured as a board 1 inch thick, 12 inches wide, and 12 inches long. Other dimension combinations can contain the same volume, so a board foot is not a fixed board shape.
Should I use nominal or actual lumber dimensions?
Use the dimensions on which the seller bases board-foot pricing. Hardwood and rough lumber are often tallied before or at stated surfacing stages, while construction lumber uses nominal trade names that differ from actual size. Ask the yard when the pricing basis is unclear.
How many board feet are in a 2×4×8 board?
Using nominal dimensions, 2 × 4 × 8 ÷ 12 equals 5.33 board feet. Using an actual dressed size of 1.5 by 3.5 inches gives 3.5 board feet. The appropriate answer depends on which dimensions the supplier uses for the transaction.
How much waste should I add when buying hardwood?
A simple project using clear, consistent boards may need about 10% extra, while visible grain matching, rough stock, defects, or many short parts can justify 20%–30% or more. Build a cut list and inspect the grade before selecting an allowance.
Sources and reference standards
- USDA Forest Products Laboratory — Wood HandbookFederal reference for wood characteristics, lumber terminology, dimensions, moisture, and structural use.
- National Institute of Standards and Technology — SI Units: LengthPrimary federal reference for customary-to-metric length relationships and unit definitions.
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