How to use the board foot calculator
- Measure the board thickness and width in inches, then the length in feet. For metric input, use millimeters for the cross section and meters for length.
- Enter how many boards have those dimensions. Use separate calculations for boards with different dimensions.
- Add your quoted price per board foot to estimate the material cost. Taxes, delivery, and unusable defects are not included.
The formula
Worked example
Ten boards, each 1 inch thick, 6 inches wide, and 8 feet long, contain 40 board feet. At $6 per board foot, the material cost is $240.
Before you measure and cut
A board foot is a volume: 144 cubic inches, or a piece 12 × 12 × 1 inch. It is not the same as a square foot or a linear foot.
Hardwood thickness is often quoted in quarters: 4/4 means 1 inch rough thickness; 6/4 means 1½ inches; 8/4 means 2 inches. Surfacing reduces finished thickness.
For a finished-volume calculation, enter actual measurements. For a purchasing estimate, use the supplier’s billing dimensions, which may be based on rough stock.
One board foot equals 0.083333 cubic feet or exactly 0.002359737216 cubic meters. With all three dimensions in inches, divide by 144 instead of 12.
Board feet in common lumber sizes
These examples use the listed cross section and one 8 ft board. They describe volume, not a supplier’s billing rules.
| Thickness × width | Length | Board feet |
|---|---|---|
| 1 × 4 in | 8 ft | 2.667 |
| 1 × 6 in | 8 ft | 4 |
| 1 × 8 in | 8 ft | 5.333 |
| 1 × 12 in | 8 ft | 8 |
| 1.5 × 3.5 in | 8 ft | 3.5 |
| 1.5 × 5.5 in | 8 ft | 5.5 |
| 2 × 4 in | 8 ft | 5.333 |
| 2 × 6 in | 8 ft | 8 |
| 2 × 8 in | 8 ft | 10.667 |
For a mixed order, calculate each size separately, then add its board feet. If prices differ by species, grade, or thickness, calculate each group’s cost separately too.
Read how to calculate board feet for a complete mixed-order example, or check nominal versus actual lumber sizes before choosing dimensions.
Frequently asked questions
How many board feet are in a 2×4×8?
Using nominal 2 × 4 inch dimensions and 8 feet of length gives 5.333 board feet. Using actual 1.5 × 3.5 inch dimensions gives 3.5 board feet. Ask whether you need nominal purchasing volume or actual finished volume.
How do I calculate board feet in metric?
Multiply thickness in millimeters, width in millimeters, length in meters, and quantity, then divide by 2359.737216. The result is board feet.
Should I add extra for waste?
First calculate the net volume. Then allow for your specific defects, grain selection, milling loss, and joinery. There is no single waste percentage that fits every project.