A board foot calculator works out how much lumber is in a board or a whole cut list, measured in board feet. One board foot is 144 cubic inches: a piece 1 inch thick, 12 inches wide and 1 foot long. Board feet = thickness (in) × width (in) × length (ft) ÷ 12. Contruva’s free board foot calculator does that for every line of your list, adds waste, and prices it at your cost per board foot.
Open the free board foot calculator in your browser. No login, no email, nothing to pay.
Open the free toolIt reads thickness the way lumber yards write it (4/4, 5/4, 8/4), takes lengths in feet or inches, and also gives linear feet, cubic feet and cubic metres. No login. Below is the formula, the nominal-size rule that trips people up, a worked order you can check by hand, and how yards actually price hardwood and framing lumber.
How to use the board foot calculator
Hardwood is usually listed in feet. Furniture cut lists are often in inches. Switching converts the lengths you’ve already entered.
Thickness in quarters (5/4), fractions (3/4), mixed numbers (1 1/2) or decimals, then width in inches, length and quantity.
Each row has its own price, so oak, maple and cedar can sit on the same list.
The calculator adds it to the board feet and the cost.
Board feet per row and in total, board feet to buy with waste, linear feet, cubic feet, cubic metres, cost and your blended price per board foot.
The board foot formula
Everything comes back to 144 cubic inches. Pick whichever version matches the units on your list:
| Your measurements | Formula |
|---|---|
| Thickness (in), width (in), length (ft) | T × W × L ÷ 12 |
| Thickness (in), width (in), length (in) | T × W × L ÷ 144 |
| Several identical boards | Quantity × T × W × L ÷ 12 |
| Board feet to cubic feet | Board feet ÷ 12 |
| Board feet to cubic metres | Board feet × 0.00236 |
A 2×4 that’s 8 ft long is 2 × 4 × 8 ÷ 12 = 5.33 board feet. A 4/4 oak board 6 in wide and 8 ft long is 1 × 6 × 8 ÷ 12 = 4 board feet. A cubic metre is about 424 board feet, which is handy when a supplier quotes in metric.
Hardwood thickness is written in quarter inches: 4/4 is 1 in, 5/4 is 1¼ in, 6/4 is 1½ in, 8/4 is 2 in, 12/4 is 3 in and 16/4 is 4 in. Type the quarter straight into the calculator.
Nominal vs actual size
Board feet are figured on the nominal size, not what the tape reads after the board is planed. That’s the convention for both hardwood and softwood, and it’s why your board feet won’t match a calculation off the finished board.
| Lumber | Nominal (what you enter) | Typical actual size |
|---|---|---|
| Framing 2×4 | 2 × 4 in | 1½ × 3½ in |
| Framing 2×6 | 2 × 6 in | 1½ × 5½ in |
| Framing 2×10 | 2 × 10 in | 1½ × 9¼ in |
| Hardwood 4/4, rough | 1 in thick | About 1 in, varies by mill |
| Hardwood 4/4, surfaced two sides | 1 in thick | Commonly 13/16 in |
| 5/4×6 decking | 1¼ × 6 in | About 1 × 5½ in |
So when you buy 4/4 hardwood surfaced to 13/16 in, you still pay for 1 in of thickness. The difference was there when the board was rough-sawn and went into the planer shavings. Width works differently with hardwood: rough boards come in random widths, and the yard measures each board’s actual width when it tallies the board feet. Ask how your yard tallies before you compare prices between them.
Worked example: a mixed hardwood order
A built-in and a cedar bench, all on one order. Prices are sample numbers to show the math, not market prices.
| Line | Board feet | Price | Cost |
|---|---|---|---|
| 4 × 4/4 red oak, 6 in × 8 ft | 4 × 1 × 6 × 8 ÷ 12 = 16 | $9.00 / BF | $144.00 |
| 2 × 8/4 hard maple, 8 in × 10 ft | 2 × 2 × 8 × 10 ÷ 12 = 26.67 | $11.00 / BF | $293.33 |
| 10 × 5/4 cedar, 6 in × 12 ft | 10 × 1.25 × 6 × 12 ÷ 12 = 75 | $6.50 / BF | $487.50 |
| Cut list total | 117.67 | $7.86 / BF average | $924.83 |
117.67 × 1.15 with 15% for defects and milling.
$924.83 × 1.15.
4 × 8 + 2 × 10 + 10 × 12.
117.67 ÷ 12, and 117.67 × 0.00236.
Notice the cedar line. It’s the cheapest wood per board foot but the biggest line on the bill, because ten 5/4 boards at 12 ft add up. The blended price of $7.86 a board foot is the number to compare against a supplier’s package quote.
How lumber is priced
Not all lumber is sold by the board foot, and mixing the two systems is how quotes go wrong.
| Lumber | Usually sold by | What to enter |
|---|---|---|
| Hardwood (oak, maple, walnut, cherry) | Board foot, rough or surfaced | Nominal thickness in quarters and the price per BF |
| Framing lumber (SPF, pressure-treated) | The piece, by size and length | Use the calculator for volume only, or divide the piece price by its board feet |
| Trim, mouldings and decking | Linear foot or the piece | Linear feet from the calculator, priced separately |
| Large wholesale orders | Thousand board feet (MBF) | Price per MBF ÷ 1,000 = price per BF |
To compare framing lumber on a board-foot basis, divide the piece price by its board feet. A 2×4×8 at $5.33 is $1.00 a board foot; the same price for a 2×6×8 (8 board feet) is about $0.67. It’s a quick way to see which size gives you the most wood for the money, or whether a mill’s price on rough timbers beats the yard.
Board feet per foot for common sizes
Multiply by the length in feet to get board feet. The calculator shows the same table beside your results.
| Nominal size | Board feet per linear foot | 8 ft piece | 12 ft piece |
|---|---|---|---|
| 1×6 (4/4 × 6) | 0.5 | 4 | 6 |
| 5/4×6 | 0.625 | 5 | 7.5 |
| 2×4 | 0.667 | 5.33 | 8 |
| 2×6 | 1.0 | 8 | 12 |
| 2×8 | 1.333 | 10.67 | 16 |
| 2×10 | 1.667 | 13.33 | 20 |
| 2×12 | 2.0 | 16 | 24 |
| 4×4 | 1.333 | 10.67 | 16 |
| 6×6 | 3.0 | 24 | 36 |
How much waste to add
Board feet in a cut list are the parts you keep. You buy more than that, because of defects, end checks, knots, and the saw kerf and planer passes between rough stock and finished parts.
- Surfaced (S4S) stock for simple parts: 5 to 10%.
- Rough hardwood you’ll joint, plane and rip: 15 to 20% is a common starting point, more for low grades.
- Figured or wide boards where you’re choosing grain: more again. You’ll set aside boards that don’t match.
- Long, clear parts: price them on longer boards. A 7 ft part can’t come out of the 6 ft offcut.
If you buy by the board, round each line up to whole boards after the calculator gives you the board feet. A list that needs 26.67 board feet of 8/4 maple might mean three boards, not two and two-thirds.
From board feet to a quote
Lumber cost is one line of a millwork or carpentry quote. Add finishing materials, shop time, install hours at your real rate, delivery, and your markup. The contractor hourly rate calculator sets the labour rate and the markup calculator turns total cost into price. For decks and fences, the deck calculator and fence calculator count the framing and boards for you.
If you quote carpentry every week, Contruva keeps your materials, costs and markup in a price catalog, so a quote goes out in minutes and the customer can sign and pay a deposit online with card payments. Job costing then shows what you spent on lumber against what you priced. It’s built for general contractors and trades alike, in one plan, Contruva Pro, at $249.99 CAD a month. Try it free for 7 days, no credit card needed.