Board Foot Calculator
Board feet of lumber & total cost
Ten boards 1 inch thick, 6 inches wide and 8 feet long are 40 board feet, 4 per board. Enter the thickness, width, length and number of boards for the total board feet, the volume unit lumber is priced in, and the cost at your price per board foot.
What is a board foot?
A board foot is a volume of lumber 1 inch thick, 12 inches wide and 12 inches long — 144 cubic inches. It is how rough and hardwood lumber is sold, because it folds thickness, width and length into a single number you can put a price against.
Board feet = thickness (in) × width (in) × length (ft) ÷ 12, multiplied by the number of pieces.
The 12 in the denominator is what confuses people: it is there because length is in feet while thickness and width are in inches. Put all three in inches and you would divide by 144 instead.
| Size | Length | Per piece | 10 pieces |
|---|---|---|---|
| 1 × 6 | 8 ft | 4.00 bd ft | 40.00 |
| 1 × 8 | 10 ft | 6.67 bd ft | 66.67 |
| 2 × 4 | 8 ft | 5.33 bd ft | 53.33 |
| 2 × 6 | 10 ft | 10.00 bd ft | 100.00 |
| 2 × 8 | 12 ft | 16.00 bd ft | 160.00 |
| 2 × 10 | 16 ft | 26.67 bd ft | 266.67 |
| 4 × 4 | 8 ft | 10.67 bd ft | 106.67 |
Nominal vs actual lumber: it changes the answer by a third
This is the trap on this page. A "2 × 4" is not 2 inches by 4 inches — it is 1½ by 3½ once dried and surfaced. The nominal name describes the rough sawn size before milling, and the wood you buy is smaller.
| Basis | Dimensions | Board feet |
|---|---|---|
| Nominal (how it is sold) | 2 × 4 in | 5.33 bd ft |
| Actual (what you measure) | 1.5 × 3.5 in | 3.50 bd ft |
| Difference | 34% less | |
The rule that resolves it: softwood dimensional lumber is priced by nominal size, so use the name on the tag — 2 × 4, not 1.5 × 3.5. Measuring the board and entering the real dimensions will understate your board feet by about a third and undercount your bill.
Hardwood thickness quarters work differently, and any lumber calculator has to treat them separately. Hardwood is sold by actual thickness expressed in quarter inches: 4/4 is one inch, 5/4 is 1¼, 6/4 is 1½, 8/4 is two. Those are rough thicknesses before surfacing, so a surfaced 4/4 board measures about 13⁄16 inch but is still sold and priced as 4/4. Width and length are actual.
| Called | Rough thickness | Surfaced (S2S) |
|---|---|---|
| 4/4 | 1 in | ~13⁄16 in |
| 5/4 | 1¼ in | ~1⅛ in |
| 6/4 | 1½ in | ~1⅜ in |
| 8/4 | 2 in | ~1¾ in |
Board feet vs linear feet
Linear feet measure length alone and ignore the cross-section entirely, so they only work when every piece is the same width and thickness. Board feet measure volume. A 2 × 12 holds six times the board feet of a 1 × 4 at the same length, and a linear-foot price would treat them the same.
- Use board feet for rough and hardwood lumber, where widths vary board to board.
- Use linear feet for trim, moulding and any fixed profile sold by the foot.
- They are numerically equal only for a 1 × 12, which is exactly one board foot per foot of length.
Buying rough lumber
Hardwood is usually quoted in dollars per board foot, and yards calculate it on the rough dimensions before you surface or joint anything — you pay for wood that ends up on the shop floor. Add 10 to 15% beyond your finished requirement for defects, trimming, snipe and the board that turns out to have a check running through it.
- Boards are measured at their narrowest point, and rough stock rarely has parallel edges.
- Grades matter to yield. FAS gives long clear cuts; Select and Common grades cost less but need more culling, which changes how much you should buy rather than just the price.
- Random width and length is normal for hardwood. Plan cuts around what you get rather than expecting uniform stock.
- Buy it all together for colour and grain consistency across a project.
Building with dimensional lumber instead? The deck board, fence and stair calculators count pieces rather than volume, which is how softwood is usually bought.
What the board-foot total assumes
Board feet are thickness (in) × width (in) × length (ft) ÷ 12, multiplied by the piece count. The divisor is 12 because length is in feet while the other two dimensions are in inches; all three in inches would divide by 144.
- Enter nominal dimensions for softwood — 2 × 4, not 1.5 × 3.5 — because that is the basis lumber is priced on. Using actual dimensions understates a 2 × 4 by 34%.
- Enter actual dimensions for hardwood, with thickness in quarters expressed as inches: 4/4 as 1, 8/4 as 2. Hardwood width and length are actual, and yards measure at the board's narrowest point.
- Rough basis. Hardwood is charged on rough dimensions before surfacing, so the board feet you pay for exceed the finished volume you keep.
- No waste allowance is applied. Add 10 to 15% yourself for defects, trimming and snipe, and more in lower grades.
- Not modelled: grade yield, random width and length stock, kerf loss, and the difference between rough and surfaced dimensions.
Reviewed September 2026.
Both unit systems. Metric mode takes millimetres and metres and prices timber by the cubic metre, with the board-foot equivalent alongside it (1 board foot is 0.00236 m³).
Figures reviewed . Every worked example on this page is checked against the calculator above.
Board Foot Calculator: frequently asked questions
How do I calculate board feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12, and multiply by the number of pieces. An 8 ft 2 × 4 is 2 × 4 × 8 ÷ 12 = 5.33 board feet.
Should I use nominal or actual dimensions for board feet?
Nominal for softwood dimensional lumber, since that is how it is priced. An 8 ft 2 × 4 is 5.33 board feet nominally but only 3.50 by its actual 1.5 × 3.5 inch size — a 34% difference, and using actual would undercount your bill.
Why is a 2x4 not actually 2 by 4 inches?
The nominal name describes the rough sawn size before the board is dried and surfaced. A finished 2 × 4 measures 1½ by 3½ inches. Lumber is still sold and priced under the nominal name.
What does 4/4 mean in lumber?
Rough thickness in quarter inches: 4/4 is one inch, 5/4 is 1¼, 6/4 is 1½ and 8/4 is two. Hardwood is priced this way before surfacing, so a surfaced 4/4 board measures about 13/16 inch but is still sold as 4/4.
Are board feet the same as linear feet?
No. Linear feet measure only length, ignoring the cross-section; board feet measure volume. A 2 × 12 holds six times the board feet of a 1 × 4 at the same length. They are equal only for a 1 × 12.
How many board feet are in a 2x4x8?
5.33 board feet using nominal dimensions, which is how it is priced. Ten of them is 53.33 board feet.
How much extra hardwood should I buy?
10 to 15% above your finished requirement, and more in lower grades. Rough lumber is measured before surfacing, so you pay for material that ends up as shavings, and random-width stock means some boards will not yield the cut you wanted.
What does FAS mean in hardwood grading?
First and Seconds, the top grade, yielding long clear cuts with few defects. Select and Common grades cost less but need more culling, so the grade changes how much you should buy rather than just the price per board foot.