How this calculator works
Board feet measure lumber by volume rather than by piece, which is how hardwood and specialty softwood are typically priced. Pick a nominal thickness using standard 'quarters' notation (4/4 for 1 inch, 8/4 for 2 inches, and so on) or enter a custom thickness in inches, give the board's width and length, how many identical pieces you need, and a price per board foot, and this calculator returns the total board feet and total cost.
The board foot is formally defined as 144 cubic inches of wood — exactly the volume of a 1 inch by 12 inch by 12 inch board. Any board's board-foot count is thickness (inches) × width (inches) × length (feet), divided by 12 — or, equivalently, thickness × width × length all in inches, divided by 144. Standard framing lumber (2×4s, 2×6s, and so on) is normally sold by the linear foot instead, so board-foot pricing mostly shows up with hardwoods and specialty rough-sawn or surfaced stock.
The formula
Board feet = thickness (in) × width (in) × length (ft) ÷ 12, equivalently thickness × width × length (in) ÷ 144Total board feet = board feet per piece × quantity; total cost = total board feet × price per board footQuarters notation ('4/4', '8/4') states the nominal rough-sawn thickness, which is what board-foot pricing is quoted against — see the surfaced-lumber note below for why the board in your hand often measures thinner.
Worked example: five 8/4 × 6 in × 8 ft boards at $6/board foot
- 8/4 is nominally 2 inches thick. Board feet per piece: 2 × 6 × 8 ÷ 12 = 8 board feet.
- Five pieces: 5 × 8 = 40 board feet total.
- At $6 per board foot: 40 × $6 = $240.
- Check with the 144 cubic inch definition: 2 × 6 × 96 (8 ft in inches) ÷ 144 = 8 board feet per piece — the same answer.
Frequently asked questions
Why does my board measure thinner than its nominal 4/4 or 8/4 size?
Quarters notation states the rough-sawn thickness before surfacing. A surfaced-two-sides (S2S) 4/4 board is typically planed down to about 13/16 inch, and 8/4 to roughly 1¾ inches, since planing removes material to create smooth, flat faces. Board-foot pricing is still based on the nominal rough thickness, not the finished measured thickness.
Is a board foot the same as a square foot?
No — a board foot is a volume measurement (144 cubic inches) while a square foot is an area measurement. A thicker board of the same width and length contains more board feet even though it covers the same floor or surface area.
Why is framing lumber (2x4s, 2x6s) usually priced per linear foot instead?
Standard dimensional softwood framing lumber comes in a small number of fixed cross-sections, so pricing by the linear foot is simpler for both retailers and buyers. Board-foot pricing is more common for hardwoods and specialty stock, which come in a wider range of thicknesses and widths and are often sold by weight or volume from a sawmill.
Does board-foot pricing include waste from milling or drying?
No — this calculator computes the board-foot volume of the finished pieces you specify. Actual purchased volume is often higher once you account for kerf loss from resawing, planing allowance, and defect culling, especially when buying rough lumber to mill yourself.
How many board feet are in a single 4/4 × 8 in × 10 ft board?
About 6.67 board feet. A 4/4 board is nominally 1 inch thick, so using the board-foot formula (thickness in inches × width in inches × length in feet ÷ 12): 1 × 8 × 10 ÷ 12 = 80 ÷ 12 ≈ 6.67 board feet.