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This board foot calculator works out the volume of lumber in board feet, the unit used to price hardwood and many specialty lumbers in North America. Enter the thickness and width in inches, the length in feet and the number of boards, and add the price per board foot to estimate the cost.
What Is a Board Foot?
A board foot is a volume of wood 12 inches long, 12 inches wide and 1 inch thick, which is 144 cubic inches or 1/12 of a cubic foot. Hardwood dealers price lumber by the board foot, while home centers usually price softwood framing lumber by the piece or by the linear foot.
Board Foot Formula
Board feet = Thickness (in) × Width (in) × Length (ft) ÷ 12
If you measure the length in inches, divide thickness × width × length by 144 instead.
Worked Example
Ten 2 × 6 boards, 8 ft long: 2 × 6 × 8 ÷ 12 = 8 board feet each, so 80 board feet in total. At $1.50 per board foot, that is $120.
Board Feet for Common Lumber Sizes
| Nominal size | Board feet per linear foot | 8 ft board | 10 ft board | 12 ft board |
|---|---|---|---|---|
| 1 × 4 | 0.333 | 2.67 | 3.33 | 4 |
| 1 × 6 | 0.5 | 4 | 5 | 6 |
| 2 × 4 | 0.667 | 5.33 | 6.67 | 8 |
| 2 × 6 | 1 | 8 | 10 | 12 |
| 2 × 8 | 1.333 | 10.67 | 13.33 | 16 |
| 2 × 10 | 1.667 | 13.33 | 16.67 | 20 |
| 4 × 4 | 1.333 | 10.67 | 13.33 | 16 |
Nominal vs Actual Size
Softwood lumber is named by its rough size before drying and planing. A 2 × 4 actually measures about 1½ × 3½ inches. Board feet are normally calculated using the nominal size. Hardwoods are sold by rough thickness in quarters of an inch: 4/4 is 1 inch, 5/4 is 1¼ inch and 8/4 is 2 inches.
Tips for Buying Lumber
- Add 15–20% extra for defects, knots and cutting waste in hardwood projects.
- Ask whether the price is per board foot, per linear foot or per piece.
- Building a deck? Our deck calculator counts boards and joists, and the deck cost calculator estimates the budget.
Frequently Asked Questions
How do I calculate board feet?
Multiply the thickness in inches by the width in inches by the length in feet, then divide by 12.
How many board feet are in a 2×4×8?
Using nominal dimensions, a 2 × 4 that is 8 ft long contains 5.33 board feet.
How many board feet are in a cubic foot?
12 board feet make one cubic foot.
Is board footage calculated with nominal or actual size?
Usually with the nominal (named) size for softwood lumber and the rough thickness for hardwoods.
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