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Board Foot Calculator
Board foot maths and lumber guidance from Go4Wood — The craft community for makers — learn, build, share, and shop.
See it on Go4WoodYour boards
Thickness × width × length for each piece. Press Enter to add another row.
Board 1
Need real prices? Go4Wood's Species Database lists typical cost per board foot by species.
Waste allowance
Rough lumber loses roughly ⅛″–¼″ of thickness when it's milled flat, and defects and snipe cost you more. Add the percentage you actually buy over.
Total board feet
0.00 BF
Estimated lumber cost
Add a cost per board foot to any row to price the order.
Formula: board feet = (thickness × width × length) ÷ 144 when every dimension is in inches. One board foot is 144 cubic inches — a 1″ × 12″ × 12″ board.
A worked example
Three boards of 8/4 walnut, 8 inches wide and 8 feet long. Thickness is 2″, width is 8″, and the length is 8 ft, so each board is 2 × 8 × 96 ÷ 144 = 10.67 board feet. Three of them come to 32 board feet.
At an illustrative $14 per board foot that's 32 × 14 = $448 of lumber. Add a 15% waste allowance and you're buying 36.8 board feet instead — about $515. Whether $14 is anywhere near right for walnut where you live is a different question, and the one Go4Wood's Species Database exists to answer.
Why the units matter
Lumber is quoted with mixed units more often than not: thickness and width in inches, length in feet. That's the default here — Length in feet. The other two modes treat every dimension the same way, so pick All inches if you've already converted, and All feet if you're working in cubic feet (one cubic foot is 12 board feet).
Getting this wrong is the single most common way a board foot total ends up off by a factor of twelve.
Common questions
- What is a board foot?
- 144 cubic inches of lumber — a board 1 inch thick, 12 inches wide and 12 inches long. It's a measure of volume, which is why a 1×12 and a 2×6 of the same length come to the same board footage.
- How do you calculate board feet?
- Multiply thickness × width × length in inches and divide by 144. When the length is in feet instead, divide by 12: thickness (in) × width (in) × length (ft) ÷ 12.
- What do 4/4, 5/4 and 8/4 mean?
- Quarters of an inch of rough thickness, the way sawmills sell hardwood. 4/4 is one inch, 5/4 is an inch and a quarter, 8/4 is two inches. Type the decimal into the thickness field — the suggestions list shows which quarter each one is.
- Should I use rough or finished dimensions?
- Rough. You buy the board at its rough size and lose some of it at the jointer and planer — Go4Wood puts that at roughly an eighth to a quarter of an inch of thickness to get a board flat. Costing the finished part under-buys the lumber.
- How much waste should I add?
- It depends on the board and the build — defects, snipe, cutting around knots and figure, and how forgiving your part sizes are all move it. Narrow parts cut from wide boards waste more than a straight rip. Use your own recent orders as the guide rather than a rule of thumb, which is why the waste allowance here starts at zero.
- Board feet, linear feet or square feet?
- Board feet measure volume and are how rough hardwood is priced. Linear feet measure length only, and are how trim and dimensional softwood are usually sold. Square feet measure area, and are how sheet goods like plywood are sold.
Now price the whole job
Lumber is one line on a quote. Quote It Right takes the materials, your shop time, overhead and margin and turns them into a price you can send — and the Pay Yourself Calculator works out what your shop hour has to earn in the first place.