Board Foot Calculator
Hardwood is sold by the board foot, not the board. Enter your boards below and this gives you the board feet for each one, the total for the project, and what it costs at your yard's price.
| Part | Thickness (in) | Width (in) | Length (in) | Qty | Board ft | Remove |
|---|
What a board foot actually is
A board foot is a volume, not a length or an area. One board foot is 144 cubic inches: think of a piece 1 inch thick, 12 inches wide and 12 inches long. That is why two boards with the same footprint can cost very different amounts if one is thicker.
The formula, with everything in inches:
board feet = (thickness × width × length) ÷ 144
Or if your length is in feet:
board feet = (thickness × width × length in feet) ÷ 12
Quarter thickness, and why 4/4 is not 1 inch
Hardwood yards talk in quarters. 4/4 ("four quarter") is nominally 1 inch, 8/4 is 2 inches, and so on. The catch is that rough stock is measured before it is surfaced. A 4/4 board that has been planed on both faces will land nearer 13/16 inch, but you are usually charged for the 1 inch you started with. Ask the yard whether the price is for rough or surfaced stock, because it changes the sum.
| Called | Nominal thickness | Typical after surfacing |
|---|---|---|
| 4/4 | 1" | 13/16" |
| 5/4 | 1 1/4" | 1 1/16" |
| 6/4 | 1 1/2" | 1 5/16" |
| 8/4 | 2" | 1 3/4" |
Why the waste allowance matters
Nobody uses every inch of a board. You lose material to defects, to squaring the ends, to ripping a straight edge, and to the saw kerf on every cut. Ordering exactly the board feet in your cut list is how you end up back at the yard. Twenty percent is a sensible default for reasonably clean stock; push it to thirty for rough-sawn or heavily figured timber where you will be cutting around problems.
Softwood is different
Construction lumber is usually sold by the piece at a nominal size, so a "2x4" is really 1 1/2 by 3 1/2 inches. If you are buying 2x4s and studs rather than hardwood by volume, the cut list calculator is the more useful tool: it tells you how many boards to buy and where to cut them.
Not sure which species to buy in the first place? Start with types of wood for beginners, or plywood vs MDF vs solid wood if you are weighing sheet goods against solid timber. To weigh the load rather than price it, use the lumber weight calculator, and the full set of calculators is here.
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