Lumber Calculator
Board feet for a single piece of lumber or a whole order, calculated from nominal length, width, and thickness, which is how a lumber yard prices it.
Total board feet
80bd ft
Per piece
8bd ft
Use nominal dimensions, the size on the tag. A 2x4 counts as 2 in by 4 in even though it actually measures 1.5 by 3.5 once dressed. Lumber is priced per board foot off the nominal size, so that is the one that matters here.
How the lumber calculator works
Board feet measure volume, not length. One board foot is a 1-inch-thick piece 12 inches square, so length, width, and thickness all push the number up. That's the point of the unit: it lets a lumber yard price wood of different sizes off a single rate.
Formula: board feet = length (ft) × width (in) × thickness (in) ÷ 12. A 2x4x8 comes out at 2 × 4 × 8 ÷ 12 = 5.33 board feet. For a full order, multiply the per-piece figure by your quantity.
Board feet tell you how much wood to buy, not what it will cost. Lumber moves more than most building materials, so before you price an order it is worth checking the Lumber Price Index to see which way the market has gone.
Frequently asked questions
One board foot is a piece 12 inches long, 12 inches wide, and 1 inch thick, or 144 cubic inches. It's a unit of volume, not length, which is the part that trips people up. Lumber yards price hardwood and larger dimensional orders this way because it lets you compare a 1x8 against a 2x4 on the same terms.
Nominal, the size printed on the tag. A 2x6 actually measures 1.5 by 5.5 inches once it's been dressed, but board footage and pricing both run off the nominal 2x6. Use the actual dressed size and your total will come out well short.
Linear footage only measures length and ignores width and thickness, so it only makes sense for a single fixed size of board (like "how many linear feet of 2x4 do I need"). Board footage measures true volume, so it works for comparing or pricing different lumber sizes against each other.
5.33 board feet. The math is 2 in thick times 4 in wide times 8 ft long, divided by 12. A 1x6x8 works out to 4 board feet the same way. For a full order, work out one piece and multiply by the quantity, which is what the quantity field above does.
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