Which unit of measure used for lumber is based on thickness by width by length?

• A. Square Foot
• B. Cubic Yard
• C. Lineal Foot
• D. Board Foot

Answer: (D)

Lumber is priced by volume in a way that captures all three dimensions of a board: thickness, width, and length. The board foot is defined so that a board that is 1 inch thick, 12 inches wide, and 12 inches long represents one board foot. This makes board feet the natural unit for describing how much wood you have when both thickness and width matter, along with length.

A practical way to think about it is: board feet = thickness (in inches) × width (in inches) × length (in feet) ÷ 12. For example, a board that is 2 inches thick, 6 inches wide, and 8 feet long equals 2 × 6 × 8 ÷ 12 = 8 board feet. This demonstrates how the unit accounts for all three dimensions.

The other options don’t fit that purpose: square foot measures area (length by width), not volume; cubic yard measures volume but uses different units and is less practical for typical lumber sizing; lineal foot measures only length without regard to thickness or width. Board feet uniquely reflect thickness by width by length.