Board Feet Calculator
Easily calculate the volume of lumber in board feet.
Lumber Dimensions
Board Feet vs. Length
Common Lumber Sizes and Board Feet
| Nominal Size (in) | Actual Size (in) | Length (ft) | Board Feet per Piece |
|---|---|---|---|
| 1×4 | 0.75 x 3.5 | 8 | 1.75 |
| 1×6 | 0.75 x 5.5 | 8 | 2.75 |
| 2×4 | 1.5 x 3.5 | 8 | 3.50 |
| 2×6 | 1.5 x 5.5 | 8 | 5.50 |
| 2×8 | 1.5 x 7.25 | 10 | 9.06 |
| 2×10 | 1.5 x 9.25 | 12 | 13.88 |
| 4×4 | 3.5 x 3.5 | 8 | 8.17 |
What is Board Feet?
A “board foot” (BF or bd ft) is a unit of volume used specifically for lumber in the United States and Canada. It represents the volume of a piece of wood that is one foot long, one foot wide, and one inch thick, or its equivalent. So, 1 board foot = 1 ft × 1 ft × 1 in = 12 in × 12 in × 1 in = 144 cubic inches. The board feet calculator helps determine this volume for any given piece of lumber.
Woodworkers, lumberyards, foresters, and anyone involved in buying, selling, or using lumber use board feet to measure and price wood. It standardizes the volume measurement regardless of the lumber’s shape after milling, focusing on the rough-sawn volume. Our board feet calculator simplifies this calculation.
A common misconception is that board feet is a measure of length or area. It is strictly a measure of volume. Another point of confusion is between nominal and actual dimensions of lumber. Nominal dimensions are the sizes before drying and surfacing (e.g., 2×4), while actual dimensions are smaller (e.g., 1.5″ x 3.5″). For accurate board feet, using actual dimensions is better, but sometimes calculations are based on nominal sizes, especially for hardwoods.
Board Feet Formula and Mathematical Explanation
The formula to calculate board feet is derived from the volume of a rectangular piece of wood, standardized to the 144 cubic inch definition.
If dimensions are in inches:
Board Feet per piece = (Thickness (inches) × Width (inches) × Length (inches)) / 144
If length is in feet:
Board Feet per piece = (Thickness (inches) × Width (inches) × Length (feet) × 12) / 144 = (Thickness (inches) × Width (inches) × Length (feet)) / 12
The board feet calculator uses these formulas.
Variables:
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| T | Thickness of the lumber | inches | 0.5 – 12 |
| W | Width of the lumber | inches | 1 – 24 |
| L | Length of the lumber | inches or feet | 1 – 24 (ft) or 12 – 288 (in) |
| BF | Board Feet | board feet | 0.1 – 200+ per piece |
Practical Examples (Real-World Use Cases)
Example 1: Buying Lumber for Decking
You need to buy 2×6 boards for your deck surface. You plan to use 50 boards, each 12 feet long. The actual dimensions of a 2×6 are 1.5 inches thick and 5.5 inches wide.
- Thickness (T) = 1.5 inches
- Width (W) = 5.5 inches
- Length (L) = 12 feet
- Quantity = 50
Using the formula: BF per piece = (1.5 × 5.5 × 12) / 12 = 8.25 BF
Total Board Feet = 8.25 BF/piece × 50 pieces = 412.5 BF. You would need to purchase approximately 412.5 board feet of lumber.
Example 2: Wood for a Tabletop
You are building a tabletop from rough-sawn walnut that is 2 inches thick, 8 inches wide, and you need 3 pieces each 6 feet long.
- Thickness (T) = 2 inches
- Width (W) = 8 inches
- Length (L) = 6 feet
- Quantity = 3
Using the formula: BF per piece = (2 × 8 × 6) / 12 = 8 BF
Total Board Feet = 8 BF/piece × 3 pieces = 24 BF. You’ll need 24 board feet of walnut for the tabletop before accounting for waste.
How to Use This Board Feet Calculator
- Enter Thickness: Input the thickness of the lumber in inches (T). Use actual dimensions if known for better accuracy.
- Enter Width: Input the width of the lumber in inches (W). Again, actual dimensions are preferred.
- Enter Length: Input the length of one piece of lumber (L).
- Select Length Unit: Choose whether the length you entered is in feet or inches from the dropdown menu.
- Enter Quantity: Specify how many pieces of lumber have these dimensions.
- View Results: The board feet calculator will instantly show the board feet per piece and the total board feet for the quantity entered.
- Reset: Click “Reset” to clear the fields to their default values.
- Copy: Click “Copy Results” to copy the main results and inputs to your clipboard.
The results from the board feet calculator help you estimate material needs and costs for your projects.
Key Factors That Affect Board Feet Results
- Actual vs. Nominal Dimensions: Nominal dimensions (like 2×4) are before drying and surfacing. Actual dimensions (like 1.5″ x 3.5″) are smaller. Using actual dimensions gives a more accurate board foot measure of the wood you receive. The board feet calculator works with whatever you input, but be aware of the difference.
- Length Unit: Ensure you select the correct unit (feet or inches) for the length measurement to get an accurate calculation from the board feet calculator.
- Quantity of Pieces: The total board feet directly scales with the number of pieces.
- Rounding: Lumberyards may round board feet calculations up or down. Our board feet calculator provides a precise value.
- Waste Factor: When planning projects, always add a waste factor (5-15%) to the total board feet calculated, as cutting and defects will result in some unusable wood. Check our Wood Waste Calculator for more.
- Kerf Width: The width of the saw blade (kerf) removes material with each cut, which can add up over many cuts, effectively reducing your usable volume slightly.
- Wood Species: While board feet is a volume measure, the density and cost per board foot vary significantly between species (e.g., pine vs. oak).
Frequently Asked Questions (FAQ)
A: It’s a traditional unit in the North American lumber industry, specifically dealing with lumber that is typically milled to standard thicknesses, often around one inch, making the 144 cubic inch base convenient.
A: The calculator measures the volume based on the dimensions you input. If you input dimensions of green lumber, the board feet will be higher than if you input dimensions of dried lumber due to shrinkage.
A: Calculating board feet in logs is more complex and uses log scaling rules (like Doyle, Scribner, or International 1/4″ rule) which estimate the amount of sawn lumber obtainable. This board feet calculator is for sawn lumber.
A: No. Linear feet is just a measure of length, while board feet is a measure of volume.
A: Hardwoods are often priced per board foot, while softwoods (like framing lumber) are often priced per piece or per linear foot, though the underlying cost is related to board feet. Use our Lumber Cost Estimator.
A: For irregular shapes, you’d typically estimate the average thickness, width, and length to use in the board feet calculator, or use more complex volume calculations.
A: In lumber terminology, thickness is usually the smaller dimension of the cross-section, and width is the larger, but the board feet calculator just needs three orthogonal dimensions.
A: Explore resources about types of lumber and understanding lumber grades.
Related Tools and Internal Resources
- Wood Waste Calculator: Estimate waste when cutting lumber for projects.
- Lumber Cost Estimator: Calculate the total cost of lumber based on price per board foot or per piece.
- Woodworking Project Planner: Plan materials and cuts for your woodworking projects.
- Types of Lumber Guide: Learn about different wood species and their uses.
- Understanding Lumber Grades: A guide to the grading standards for lumber.
- DIY Deck Building Guide: Information on planning and building your own deck.