Board Foot Calculator
Hardwood is priced by the board foot — a volume equal to a 12×12×1 inch board. Enter your lumber dimensions to get board feet and cost, instantly, in your browser.
Board Foot Calculator
About this board foot calculator
Lumberyards sell hardwood by the board foot, not by the board. One board foot is 144 cubic inches of wood — the volume of a board 12 inches wide, 12 inches long, and 1 inch thick. The formula is (thickness in inches × width in inches × length in feet) ÷ 12.
Note that lumber dimensions here are actual dimensions, not nominal. A "2x4" is actually 1.5 × 3.5 inches — but board-foot pricing for construction softwood is usually quoted per piece anyway. This calculator shines for hardwoods (oak, walnut, maple, cherry) where per-board-foot pricing is the norm and a miscalculation gets expensive fast.
Enter an optional price per board foot and the calculator totals your materials cost — handy when comparing species or deciding whether that walnut upgrade fits the budget.
Worked example: pricing a walnut bookshelf project
Say your bookshelf design calls for 20 boards of walnut, each measuring a true 3/4 inch thick, 7-1/4 inches wide, and 10 feet long, and your lumberyard quotes $9.50 per board foot. Per board: (0.75 × 7.25 × 10) ÷ 12 = 4.53 board feet. For 20 boards: 4.53 × 20 = 90.63 board feet. At $9.50 per board foot, the lumber costs about $860.94 before waste.
Furniture-grade work needs a waste allowance for defects, miscuts, and grain matching — 20% is the standard. That brings the buy to 90.63 × 1.2 = 108.75 board feet, or about $1,033.13 total. Notice how the waste allowance alone adds over $170: skipping it is the classic way a hardwood project blows its budget.
Buying tips
Hardwood is sold rough (thickness in quarters: 4/4, 5/4, 8/4) or surfaced (S2S/S4S). Surfaced boards cost more per board foot because the mill did the planing — but if you do not own a planer, the premium is usually worth it. Always check moisture content with a meter before buying: 6–8% is right for indoor furniture. Wood bought wet shrinks, cups, and twists as it dries in your shop, and no calculator can fix that.
When comparing lumberyards, normalize everything to dollars per board foot — and confirm whether each quote is for rough or surfaced stock. A yard quoting $9.50/bf rough beats $10.25/bf surfaced only if you can surface it yourself; otherwise the surfaced board is the better deal.
How to use
- Measure the actual thickness and width of your boards in inches and the length in feet.
- Enter how many identical boards you need.
- Optionally add the price per board foot from your lumberyard quote.
- Press Calculate for total board feet and estimated cost.
Good to know
- Uses actual (not nominal) dimensions — measure the wood, don't trust the label.
- Does not account for waste, defects, or planing loss; buy 15–20% extra for furniture-grade work.
- Prices vary wildly by species, grade, and region — treat the cost figure as a planning estimate.
- Hardwood thickness is quoted in quarters of an inch (4/4 = 1 in rough, 8/4 = 2 in rough). Surfaced boards (S2S/S4S) measure thinner than their rough label — measure the actual wood.
- Check moisture content before you buy: 6–8% for indoor furniture. Wet lumber shrinks and twists as it dries, no matter how carefully you calculated.
Frequently asked questions
What is a board foot?
A board foot is a unit of lumber volume equal to 144 cubic inches — for example, a board 1 inch thick, 12 inches wide, and 12 inches long. Hardwood lumber is priced per board foot.
How do you calculate board feet?
Multiply thickness (inches) × width (inches) × length (feet), then divide by 12. A 1×6 that is 8 feet long = (1 × 6 × 8) ÷ 12 = 4 board feet.
Do I use nominal or actual dimensions?
Actual dimensions. A nominal 2x4 is really 1.5 × 3.5 inches, which changes the board-foot count. Always measure the real wood.
How many board feet are in a 2x4x8?
Using actual dimensions (1.5 × 3.5 in, 8 ft): (1.5 × 3.5 × 8) ÷ 12 = 3.5 board feet.
Why is hardwood sold by board foot instead of by the piece?
Because hardwood comes in random widths and lengths from the mill. Board feet normalize everything to pure volume, so a wide short board and a narrow long board are priced fairly.
What do 4/4, 5/4, and 8/4 mean on a lumber price list?
Lumber thickness in quarters of an inch: 4/4 is 1 inch rough (surfacing brings it to about 3/4 in), 5/4 is 1-1/4 in rough, 8/4 is 2 in rough. The board-foot formula always uses the actual measured thickness, not the quarters label.
How much extra lumber should I buy for waste?
For furniture-grade work, buy 15–20% extra for defects, miscuts, and grain matching. A project needing 60 board feet means buying 69–72. For rough shop fixtures or framing, 10% is usually enough.
How do I compare lumber prices between two yards?
Compare dollars per board foot, never price per board — and check whether each quote is for rough or surfaced stock. A $9.50/bf rough quote beats $10.25/bf surfaced only if you own a planer; otherwise the surfaced board is the better deal.
Is a board foot the same as a linear foot?
No. A linear foot measures length only. Ten linear feet of 1×6 is 5 board feet; ten linear feet of 2×12 is 20 board feet. Hardwood is priced by board feet because board widths and thicknesses vary.