Lumber Board Feet Calculator
Calculate board feet for a piece of lumber, or a full order, based on thickness, width, and length.
What a board foot actually measures
A board foot is a volume measurement, not a length — it represents a piece of wood 1 inch thick, 12 inches wide, and 12 inches long (144 cubic inches). This is why the formula divides by 12: (thickness in inches × width in inches × length in feet) ÷ 12.
This is different from a 'linear foot,' which only measures length regardless of thickness or width — lumber is often priced by board foot precisely because it accounts for the actual volume of material, not just how long a piece is.
Nominal vs. actual lumber dimensions
A key gotcha in lumber calculations: a '2x4' board isn't actually 2 inches by 4 inches — after milling and drying, its actual dimensions are closer to 1.5 by 3.5 inches. This calculator uses whatever dimensions you enter, so for accurate results, use actual (not nominal) dimensions if you're working with standard dimensional lumber.
This distinction commonly trips up DIY projects — always check actual measured dimensions with a tape measure rather than relying purely on the nominal size printed at the lumber yard.
Frequently asked questions
Why isn't a 2x4 actually 2 inches by 4 inches?
Nominal lumber sizes refer to the rough-cut dimensions before drying and planing — the finished, actual size is smaller, typically about 1.5 by 3.5 inches for a standard 2x4.
Should I use nominal or actual dimensions in this calculator?
Use actual measured dimensions for the most accurate board footage — nominal sizes will overstate the true volume of finished lumber.