Lumber Calculator Formula
Understand the math behind the lumber calculator. Each variable explained with a worked example.
Formulas Used
Board Feet per Piece
board_feet_each = bf_per_pieceTotal Board Feet
total_board_feet = bf_per_piece * quantityTotal Linear Feet
total_linear_feet = length_ft * quantityEstimated Cost
estimated_cost = bf_per_piece * quantity * price_per_bfVariables
| Variable | Description | Default |
|---|---|---|
thickness | Thickness (nominal)(inches) | 2 |
width | Width (nominal)(inches) | 6 |
length_ft | Length(feet) | 12 |
quantity | Number of Pieces | 20 |
price_per_bf | Price per Board Foot(USD) | 5 |
bf_per_piece | Derived value= thickness * width * length_ft / 12 | calculated |
How It Works
How to Calculate Lumber
Board Foot Formula
Board Feet = (Thickness × Width × Length) / 12
Thickness and width are in inches (nominal), length is in feet. One board foot is a piece 1 inch thick × 12 inches wide × 12 inches long (or 144 cubic inches). Hardwood lumber is priced by the board foot, while dimensional softwood lumber is often priced per linear foot or per piece.
Worked Example
20 pieces of 2×6 lumber, 12 ft long, at $5 per board foot.
- 01Board feet per piece = (2 × 6 × 12) / 12 = 12 BF
- 02Total board feet = 12 × 20 = 240 BF
- 03Total linear feet = 12 × 20 = 240 lin ft
- 04Cost = 240 × $5 = $1,200.00
Frequently Asked Questions
What is a board foot?
A board foot (BF) is a unit of volume equal to 144 cubic inches: 1 inch thick × 12 inches wide × 12 inches long. It is the standard unit for pricing hardwood lumber.
What is the actual size of a 2×6?
A nominal 2×6 is actually 1.5 × 5.5 inches. However, board foot calculations use the nominal (named) dimensions, not the actual dimensions.
How do I convert linear feet to board feet?
Multiply linear feet by the nominal thickness and width, then divide by 12. For a 2×6: BF = linear feet × 2 × 6 / 12 = linear feet × 1.
Learn More
Guide
Understanding Lumber Dimensions: Nominal vs. Actual Sizes
Learn the difference between nominal and actual lumber dimensions. Covers common framing sizes, board feet calculations, hardwood grading, and how to choose the right lumber for your project.
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