What the lumber calculator does
Timber in North America is priced by the board foot — a volume unit, not a length — and figuring out how many board feet a stack of 2×6s at 8 ft represents, and what it will cost, is the first step in any framing, decking or furniture estimate. Enter the thickness, width and length of a board, the quantity, and the price per board foot, and the calculator returns total board feet and total cost. Runs in your browser.
The formula
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
= thickness (in) × width (in) × length (in) ÷ 144
One board foot = 1 in × 12 in × 1 ft (144 cubic inches)
2 × 6 × 8 ft: 2 × 6 × 8 ÷ 12 = 8 board feet
10 of them: 80 bf × $1.10/bf = $88Enter nominal dimensions (2 × 6), which is how dimensional lumber is sold and priced by the board foot — even though the actual dried size is 1½ × 5½ in. Hardwood is sold by actual thickness in quarters (4/4 = 1 in, 8/4 = 2 in) and actual width.
Board feet per piece for common sizes
| Size | 8 ft | 10 ft | 12 ft | 16 ft |
|---|---|---|---|---|
| 1 × 4 | 2.67 | 3.33 | 4 | 5.33 |
| 1 × 6 | 4 | 5 | 6 | 8 |
| 2 × 4 | 5.33 | 6.67 | 8 | 10.67 |
| 2 × 6 | 8 | 10 | 12 | 16 |
| 2 × 8 | 10.67 | 13.33 | 16 | 21.33 |
| 2 × 10 | 13.33 | 16.67 | 20 | 26.67 |
| 2 × 12 | 16 | 20 | 24 | 32 |
| 4 × 4 | 10.67 | 13.33 | 16 | 21.33 |
Nominal vs actual size
| Nominal | Actual (softwood, dried) |
|---|---|
| 1 × 4 | ¾ × 3½ in |
| 2 × 4 | 1½ × 3½ in |
| 2 × 6 | 1½ × 5½ in |
| 2 × 8 | 1½ × 7¼ in |
| 2 × 10 | 1½ × 9¼ in |
| 4 × 4 | 3½ × 3½ in |
The difference comes from planing and drying after the rough cut. Use nominal sizes for board-foot pricing and actual sizes for fitting and structural calculation.
Estimating a project
- Wall framing: one stud per 16 in of wall length plus three, plus top and bottom plates (3× the wall length for a double top plate).
- Deck joists: deck width ÷ joist spacing (16 in typical) + 1, each the deck depth long; add rim joists and blocking.
- Decking boards: deck width ÷ (board width + gap) rows, each the deck length; 5½ in boards with ¼ in gaps give about 2.1 boards per foot of width.
- Waste: add 10% for cuts and defects, 15% for diagonal patterns.
- Price the list by board feet with this calculator, or by the piece if the yard prices that way — check which.
Outside North America
Most of the world sells timber by the linear metre or the cubic metre in metric sizes (45 × 95 mm, 47 × 150 mm). To compare with board-foot prices: 1 m³ = 423.8 board feet. A price of $1.10/bf is about $466/m³. The calculator works in inches and feet; convert metric sizes with the Unit Converter first.