Lumber Calculator
Calculate board feet and cost for any lumber size — 2×4, 2×6, 4×4 and more — in seconds.
A 2×4 that is 8 ft long equals 5.33 board feet ((2×4×8)/12).
How to Use This Lumber Calculator
- Enter the nominal lumber size — thickness and width in inches (e.g. 2×4).
- Enter the length in feet and the number of pieces.
- Read the total board feet and the cost at your price per board foot.
The Formula
One board foot is 1 inch thick × 12 inches wide × 1 foot long (144 cubic inches). Board feet = thickness × width × length ÷ 12. Lumber yards price most softwood by the board foot; the same unit works for hardwoods and specialty wood.
BF = (T × W × L) ÷ 12 T and W in inches, L in feet 1 BF = 144 in³ Definition: 1 in × 12 in × 1 ft Cost = BF × price Price per board foot (editable) Worked Example: 2×4 Stud
A 2×4 that is 8 ft long: BF = (2 × 4 × 8) ÷ 12 = 5.33 board feet. At $1.50 per board foot, that stud costs about $8.
Board Feet for Common Lumber
| Lumber | Length | Board feet |
|---|---|---|
| 2×4 | 8 ft | 5.33 |
| 2×4 | 12 ft | 8 |
| 2×6 | 8 ft | 8 |
| 2×6 | 12 ft | 12 |
| 2×8 | 10 ft | 13.33 |
| 4×4 | 8 ft | 10.67 |
BF = (T × W × L) ÷ 12, per piece.
Nominal vs Actual Size
Lumber is sold by its nominal size — a 2×4 measures 1.5 × 3.5 inches after planing. Board-foot pricing uses the nominal size, so the formula above matches how lumber yards charge. A 2×4 is 5.33 board feet per 8 ft stud whether you think of it as 2×4 or 1.5×3.5.
Quick Tips
- Board foot is the universal lumber unit — learn it and you can compare any supplier.
- Hardwoods are usually priced per board foot; framing lumber often per piece or per board foot.
- Add 10–15% waste for framing and cutting mistakes.
Frequently Asked Questions
What is a board foot of lumber?
A board foot is 1 inch thick × 12 inches wide × 1 foot long (144 cubic inches).
How do I calculate board feet?
Multiply thickness (in) × width (in) × length (ft) and divide by 12. A 2×4×8 is (2×4×8)÷12 = 5.33 board feet.
How many board feet are in a 2×4×8?
5.33 board feet.
What is the actual size of a 2×4?
1.5 × 3.5 inches — the 2×4 is the nominal (sale) size before planing.