How to use the board foot calculator
- Add a line for each board size: thickness and width in inches, length in feet, and how many.
- Set the extra for defects and cutting waste.
- Enter your price per board foot to see the cost.
The board foot formula
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
All in inches: thickness × width × length ÷ 144
Cost = board feet × (1 + extra) × price per board foot
Worked example
4 boards 1 × 6 × 8 ft and 2 boards 2 × 10 × 12 ft
- 1 × 6 × 8 ÷ 12 = 4 BF each, × 4 = 16 BF.
- 2 × 10 × 12 ÷ 12 = 20 BF each, × 2 = 40 BF.
- Total 56 board feet; with 10% extra, buy 61.6 BF.
Board feet per foot of length
| Size (nominal) | Board feet per linear foot | 8 ft board | 12 ft board |
|---|---|---|---|
| 1 × 4 | 0.333 | 2.67 | 4 |
| 1 × 6 | 0.5 | 4 | 6 |
| 1 × 8 | 0.667 | 5.33 | 8 |
| 2 × 4 | 0.667 | 5.33 | 8 |
| 2 × 6 | 1 | 8 | 12 |
| 2 × 10 | 1.667 | 13.33 | 20 |
| 4 × 4 | 1.333 | 10.67 | 16 |
Common mistakes to avoid
- Length in inches by mistake. In this formula, length is in feet.
- Surfaced vs rough. A board planed to 3/4" was bought as 4/4.
- Too little extra. Defects and grain matching eat more than you expect.
Frequently asked questions
What is a board foot?
A volume of wood 12 in long, 12 in wide and 1 in thick: 144 cubic inches. A board 1 in × 6 in × 8 ft is 4 board feet.
How do I calculate board feet?
Thickness (in) × width (in) × length (ft) ÷ 12. Or, with everything in inches, divide by 144. A 2 × 10 that is 12 ft long is 2 × 10 × 12 ÷ 12 = 20 board feet.
Do I use nominal or actual size?
Hardwood is measured rough, by nominal quarters (4/4 is 1 in), before planing. For softwood lumber priced per board foot, suppliers usually use the nominal size (a 2 × 4 counts as 2 × 4). Ask your supplier how they measure.
How many board feet are in a cubic foot?
12 board feet, because a cubic foot is 12 one-inch layers of 1 sq ft.
How much extra hardwood should I buy?
For furniture and cabinets, 20 to 30% to allow for knots, splits, color matching and cutting. For rough framing, 5 to 10%.