About this calculator
A board foot is a unit of lumber volume equal to a piece 1 inch thick, 12 inches wide and 12 inches long, or 144 cubic inches. Hardwood and many specialty boards are priced per board foot, so this calculator turns dimensions into the number you pay for.
The board foot formula
Board feet = thickness (in) × width (in) × length (ft) ÷ 12. When all three measurements are in inches, divide by 144 instead. Multiply by the number of pieces for a total, and by your price per board foot for the cost.
Worked example
A 2 × 6 that is 10 feet long: 2 × 6 × 10 ÷ 12 = 10 board feet. Twenty pieces of 2 × 4 × 8 ft come to 20 × (2 × 4 × 8 ÷ 12) = 106.7 board feet. At $4.50 per board foot, that is $480.
Common sizes at 8 feet long
| Nominal size | Board feet per 8 ft piece |
|---|---|
| 1 × 6 | 4.00 |
| 1 × 8 | 5.33 |
| 1 × 12 | 8.00 |
| 2 × 4 | 5.33 |
| 2 × 6 | 8.00 |
| 2 × 8 | 10.67 |
| 2 × 10 | 13.33 |
| 2 × 12 | 16.00 |
| 4 × 4 | 10.67 |
Things to watch out for
Lumber yards usually price by nominal size, so a "2 × 4" counts as 2 × 4 even though the actual board is about 1.5 × 3.5 inches. Enter the nominal size to match a quote, or the actual size to measure real wood volume. Many suppliers also round each board up and may count thin stock as 1 inch thick, so ask how your supplier measures. Add 10 to 15 percent for waste on most projects. For volume-based materials such as gravel, mulch and concrete, see the building calculators.
Frequently asked questions
Multiply thickness in inches by width in inches by length in feet, then divide by 12. If all three are in inches, multiply them and divide by 144.
A 2 × 4 × 8 ft piece is 2 × 4 × 8 ÷ 12 = 5.33 board feet, using nominal dimensions.
One cubic foot is 12 board feet, because a board foot is 144 cubic inches and a cubic foot is 1,728 cubic inches.
Use nominal sizes to match how most lumber yards quote prices. Use actual sizes when you need the true volume of wood.
Yes. Choose millimetres for thickness or width and metres for length, and the calculator converts to inches and feet first.