BoardFootWhat is a Board Foot?
Definition: A board foot is a specialized unit of measure for the volume of lumber in the United States and Canada. One board foot is numerically equal to a piece of wood that is 12 inches long, 12 inches wide, and 1 inch thick, totaling 144 cubic inches of volume.
The Basics of Wood Measurement
If you are walking into a high-end hardwood lumber yard for the first time, you might be surprised to see prices listed not by the piece or the foot, but by the "board foot." While softwoods (like the 2x4s you find at Home Depot) are often sold by the linear foot, hardwoods such as walnut, oak, and cherry are sold by volume.
This is because no two hardwood boards are the same width or length. Selling by volume ensures that the buyer pays precisely for the amount of fiber they receive, regardless of the board's specific dimensions.
Why Do We Use Board Feet?
In the timber industry, board foot (BF) is the most efficient way to track stock. For a mill, a board that is 2 inches thick (known as 8/4) contains twice as much material as a 1-inch thick (4/4) board of the same length and width. By using volume, the mill can set a single price per BF regardless of how the wood is sliced.
This system also helps in shipping and stocking, as weight is directly correlated with volume. For you, the woodworker, it allows for accurate project estimation. When you calculate that your table top needs 20 BF of white oak, you can find that volume in three wide boards or six narrow ones—the price remains the same.
The Math Behind the Measurement
The standard formula is: (Thickness in inches × Width in inches × Length in feet) / 12.
It is important to remember that length is almost always measured in feet at the yard, while thickness and width remain in inches. If your length is in inches, you must divide the final total by 144 instead of 12.
- 4/4 Lumber: This is roughly 1 inch thick.
- 8/4 Lumber: This is roughly 2 inches thick.
- Nominal Size: Yards bill based on the size before surfacing (planing).
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Go to CalculatorReal World Examples
Let's look at a common scenario: You find a beautiful piece of Black Walnut that is 10 inches wide, 8 feet long, and 1.5 inches thick (6/4 lumber).
To find the BF: (1.5 × 10 × 8) / 12 = 10 Board Feet. If the walnut is priced at $12 per BF, that single board will cost you $120.
Lumber Buying Checklist
To avoid common mistakes at the lumber yard, keep these tips in mind:
- Always bring your own tape measure; yards are busy and you need to verify sizes.
- Check the ends for "checks" (cracks). These sections don't count toward your usable volume.
- Ask if the price is for "Rough" or "S2S" (Surfaced 2 Sides).
- Maintain a 15% waste buffer in your calculations.