Board foot calculator
This board foot calculator multiplies thickness × width × length to find the board feet in your lumber, for one piece or a whole stack. Add a price per board foot to see what the order costs.
- Length in feet or inches
- Any number of pieces
- Total cost from your price per board foot
Last updated
How to use the board foot calculator
- Enter the thickness and width in inches. For softwood like a 2 × 6, use the nominal size (2 and 6), which is how lumber is tallied.
- Enter the length and pick feet or inches.
- Enter how many pieces of that size you need.
- Add the price per board foot if your yard quotes one, and read the board feet, linear feet and total cost.
The board foot formula
A board foot is a piece of wood 1 inch thick, 12 inches wide and 12 inches long, which is 144 cubic inches. To count board feet, multiply the three sizes and divide by 12 when the length is in feet, or by 144 when it is in inches.
board feet = thickness (in) × width (in) × length (ft) ÷ 12
board feet = thickness (in) × width (in) × length (in) ÷ 144
The American Softwood Lumber Standard defines board measure with nominal sizes: nominal thickness in inches × nominal width in feet × length in feet. So a 2 × 6 counts as 2 by 6 inches, even though the dry board measures 1½ × 5½ inches.
Worked example
Ten 2 × 6 boards, each 8 feet long.
- One board: 2 × 6 × 8 = 96.
- Divide by 12: 96 ÷ 12 = 8 board feet per board.
- Ten boards: 8 × 10 = 80 board feet.
That is also 80 linear feet and 80 ÷ 12 = 6.67 cubic feet of nominal lumber. At a price of $2.50 per board foot, the order would cost 80 × $2.50 = $200.
What size is a 2x4 really?
A dry 2 × 4 is 1½ inches thick and 3½ inches wide. Lumber is named by its nominal size, and the American Softwood Lumber Standard (PS 20-25, Table 3) sets the minimum dressed size of each. These are the dry sizes for boards and dimension lumber, from that table:
| Nominal size | Minimum dressed (dry) | Board feet per foot of length |
|---|---|---|
| 1 × 4 | ¾ × 3½ in | 0.33 |
| 1 × 6 | ¾ × 5½ in | 0.50 |
| 5/4 × 6 (1¼ in board) | 1 × 5½ in | 0.63 |
| 2 × 4 | 1½ × 3½ in | 0.67 |
| 2 × 6 | 1½ × 5½ in | 1.00 |
| 2 × 8 | 1½ × 7¼ in | 1.33 |
| 2 × 10 | 1½ × 9¼ in | 1.67 |
| 2 × 12 | 1½ × 11¼ in | 2.00 |
| 4 × 4 | 3½ × 3½ in | 1.33 |
Board feet per foot use the nominal size, so multiply by the length in feet to get the board feet in one piece. Green (unseasoned) lumber is dressed slightly larger, for example 1 9/16 inches for a nominal 2 inch thickness.
Board feet, linear feet or by the piece?
Home centers sell framing lumber and deck boards by the piece, so you rarely need board feet there. Board feet matter when a lumberyard or sawmill quotes a price per board foot, which is common for hardwoods, rough-sawn lumber and large orders.
- Board feet measure volume, so they let you compare a wide board with a thick one on price.
- Linear feet are just length. A 1 × 6 and a 2 × 12 that are both 10 feet long are 10 linear feet each, but 5 and 20 board feet.
- Hardwood is often sold rough in quarters of an inch: 4/4 is 1 inch, 5/4 is 1¼ inch and 8/4 is 2 inches. Ask the dealer how they measure width before you compare prices.
Building a deck? The deck calculator counts boards, joists and screws from the deck size.
Common questions
How do you calculate board feet?
Multiply thickness in inches × width in inches × length in feet, then divide by 12. A 2 × 6 that is 8 feet long is 2 × 6 × 8 ÷ 12 = 8 board feet.
How many board feet are in a 2x4x8?
A 2 × 4 that is 8 feet long has 2 × 4 × 8 ÷ 12 = 5.33 board feet, using the nominal size as the lumber standard does.
Do you use actual or nominal size for board feet?
For softwood lumber, use the nominal size. The American Softwood Lumber Standard figures board measure from nominal thickness and width, so a 2 × 6 counts as 2 by 6 inches even though it measures 1½ × 5½. Some hardwood dealers measure rough width, so ask.
How many board feet are in a cubic foot?
There are 12 board feet in a cubic foot, because a cubic foot is 1,728 cubic inches and a board foot is 144 cubic inches (1,728 ÷ 144 = 12).
What does a board foot cost?
It depends on the species, grade and region, so use your yard’s quote. Enter it in the price box and the calculator multiplies it by your total: 80 board feet at $2.50 is $200.
Sources
- NIST, Voluntary Product Standard DOC PS 20-25, American Softwood Lumber Standard. Section 2.2 board measure (nominal thickness × nominal width in feet × length in feet); Table 3 nominal and minimum dressed sizes of boards and dimension lumber. Last checked 5 November 2026
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