Board Foot Calculator
Calculate board feet of lumber from thickness, width, and length.
Price your wood purchases accurately for any woodworking project.
A board foot is the standard unit for measuring and pricing lumber in North America. One board foot equals a piece of wood 1 inch thick, 12 inches wide, and 12 inches long — or any equivalent volume: 144 cubic inches.
The formula is: Board Feet = (Thickness in inches × Width in inches × Length in feet) / 12
If your width is in inches (not feet), the formula adjusts to: BF = T × W × L / 144, where T and W are in inches and L is in inches.
This unit matters because lumber is rarely sold by the piece at a fixed price — hardwoods especially are priced per board foot, which accounts for varying thicknesses and widths. A 4/4 board (1 inch thick, also called one-quarter) of cherry might cost $8 per board foot, so knowing the total board footage of your project tells you exactly what you will spend.
Lumber thickness is commonly expressed in quarters of an inch: 4/4 = 1 inch, 5/4 = 1.25 inches, 6/4 = 1.5 inches, 8/4 = 2 inches, 12/4 = 3 inches. Always use the rough thickness when calculating board feet — not the surfaced (S4S) thickness after planing.
Example: A board that is 8/4 (2 inches thick), 6 inches wide, and 8 feet long: BF = (2 × 6 × 8) / 12 = 96 / 12 = 8 board feet. At $10/BF, that board costs $80.
Planning tip: Always add 20–30% to your calculated board footage to account for defects, grain matching, waste from cutting, and mistakes. This is called the waste factor and experienced woodworkers always include it.