Whether you are buying rough-sawn cedar for garden beds or hardwood for a greenhouse workbench, lumber pricing can be confusing. Unlike “linear feet,” which only measures length, or “square feet,” which measures surface area, lumber is sold by the Board Foot (BF)—a measurement of total volume. If you don’t know the math, you might walk out of the lumber yard paying significantly more than you budgeted.
Use our Board Foot Calculator to quickly determine the volume of your lumber list. It handles multiple sizes at once, allowing you to build a complete project estimate including total costs.
Board Foot Calculator
How to Use the Board Foot Calculator
- Thickness & Width: Enter the nominal size of the board (e.g., for a 2×4, enter 2 and 4).
- Length: The length of the board in feet.
- Quantity: The number of boards of this specific size.
- Price per BF: If the lumber yard quoted you a price per board foot, enter it here to see the total dollar amount.
- Add to List: Use this button to save your calculation and start another size. The tool will keep a running grand total for your entire project.
Why We Built This: Nominal vs. Actual Lumber
The “Secret Sauce” of this tool is the reminder regarding Nominal sizing. In the world of lumber, a “2×4″ isn’t actually 2 inches by 4 inches; it is usually 1.5″ x 3.5”. However, lumber is priced and measured based on its Nominal (rough-cut) size before it was planed smooth. Our calculator uses the Nominal dimensions to match how lumber yards calculate their billing, ensuring your estimate matches your final invoice.
Educational Guide: Understanding the Board Foot Formula
A board foot is defined as a piece of lumber that is 12 inches long, 12 inches wide, and 1 inch thick. This equals 144 cubic inches of wood.
The standard formula is: (Thickness in. × Width in. × Length ft.) / 12
Tips for Buying Garden Lumber
When building for the garden, specifically for raised beds or fence posts, you should look for Rot-Resistant species like Western Red Cedar, Redwood, or Black Locust. These woods have higher “Price per BF” rates but can last 15-20 years in contact with soil. If you choose Pressure-Treated lumber, check the “use category”—UC4A is required for ground contact, while UC3B is only for above-ground use like deck railings.
Frequently Asked Questions
Q: How many board feet are in a 2x4x8?
A: Using the formula (2 × 4 × 8) / 12, a standard 2x4x8 board contains 5.33 board feet.
Q: Is a board foot the same as a square foot?
A: No. A square foot only measures area (Length x Width). A board foot measures 3D volume, including the thickness. A 2-inch thick board that covers 1 square foot of area is actually 2 board feet.
Q: Do I use board feet for plywood?
A: No. Sheet goods like Plywood, OSB, and MDF are sold by the Square Foot or by the sheet (usually 4’x8′). The board foot measurement is reserved for dimensional lumber and timber.
