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.
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This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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