Lumber Calculator - Board-Foot Calculator Online

How to use this tool

1. Add lumber rows. Enter the thickness (in), width (in), length (ft), and quantity for each piece of lumber.
2. Set price. Enter the price per board-foot in the Price/BF column to see the cost for each row.
3. Select species. Choose the wood species for a weight estimate.
4. Review totals. See total board-feet, cost, and estimated weight at the bottom.

What is a board-foot?

A board-foot (BF) is the standard unit for measuring lumber volume in the United States. One board-foot equals a piece of wood 1 inch thick, 12 inches wide, and 1 foot long. The formula is:

Board-Feet = (Thickness × Width × Length) / 12

where thickness and width are in inches and length is in feet.

Nominal vs. actual dimensions

Lumber is sold by nominal dimensions (e.g., 2×4, 2×6) but its actual milled dimensions are smaller. A nominal 2×4 measures approximately 1.5 × 3.5 inches. Lumber suppliers typically bill by nominal dimensions for board-feet, so use nominal sizes in this calculator unless your supplier specifies otherwise.

Common lumber grades

• #1 (Construction grade): tight knots, minimal defects; used for structural framing, headers, beams.
• #2 (Standard grade): slightly more defects; the most common framing lumber for walls, floors, and roofs.
• S4S (Surfaced four sides): smooth on all four faces; used for trim, shelving, furniture.
• Common board: lower cost, used for non-structural applications like fencing, crates, and decorative projects.

Weight estimation

Weight is estimated by multiplying the wood volume by the average air-dry density of the selected species. Green (wet) lumber can weigh 50–100% more. Use the weight estimate for planning transport, not structural calculations.

Treatment and preservation

• Pressure-treated (PT): lumber impregnated with preservatives under pressure. Required for any wood in contact with ground, concrete, or in wet locations (decks, fence posts, sill plates). Modern PT uses copper-based compounds (CA-C, ACQ).
• Heat-treated (HT): lumber heated to at least 56°C to eliminate insects and pathogens. Required by IPPC regulations for wood packaging and pallets in international trade (marked with the IPPC symbol).
• Kiln-dried (KD): lumber dried in a controlled oven to a target moisture content (typically 15–19%). KD lumber is more dimensionally stable, lighter, and accepts paint/stain better than green lumber. Look for "KD-HT" stamps for both treatments.

Engineered lumber

Modern construction often uses engineered lumber products that are not measured in board-feet:

• LVL (Laminated Veneer Lumber): thin veneers glued with grain aligned in one direction - produces very strong, consistent beams used for headers, ridge beams, and long-span applications.
• I-joists: engineered floor and roof joists with an OSB web and LVL flanges. Lighter, straighter, and longer-spanning than dimensional lumber joists.
• OSB (Oriented Strand Board): wood strands layered in alternating directions and glued. Used for wall, roof, and floor sheathing - largely replaced plywood in new construction.
• Plywood: thin wood veneers glued in alternating grain directions. Stiffer and more moisture-resistant than OSB at equal thickness; still preferred for many structural and finish applications.