Lumber Calculator

What is a board foot?

A board foot is a unit of lumber volume equal to 1 inch thick × 1 foot wide × 1 foot long. It’s how sawmills and lumber yards price hardwood and construction lumber — you pay for board feet, not linear feet.

How this calculator works

• Enter the thickness (inches), width (inches), and length (feet) of your lumber.
• Board feet per piece = thickness × width × length ÷ 12.
• Enter a quantity and a price per board foot to get total board feet and total cost.
• It uses nominal sizes (a “2×4” counts as 2 × 4), matching how lumber is actually sold.

How to use the result

1. Count your pieces by size, add up the total board feet, then multiply by the price per board foot to get the material cost.
2. Compare prices across suppliers using cost per board foot — it’s the only unit that lets you compare different thicknesses and widths fairly.
3. Add 10–15% for waste and defects (knots, warping, end cuts) before buying.
4. For framing, remember studs and joists are sold by the piece or by length, not board foot — this tool is for sawn lumber and hardwood pricing.

How do I calculate board feet?

Multiply thickness (in inches) by width (in inches) by length (in feet), then divide by 12. For example, a 2 × 4 × 8 is 2 × 4 × 8 ÷ 12 = 5.33 board feet. If your length is in inches instead of feet, divide by 144.

Common mistakes

• Mixing length units. Length in feet divides by 12; length in inches divides by 144. Getting this wrong doubles or halves your answer.
• Measuring finished instead of nominal size. A “2×4” actually measures 1.5 × 3.5, but lumber is priced on the nominal 2 × 4.
• Forgetting waste. Buying exactly your net board feet leaves no room for knots, crooked boards, or cut errors.

Board feet are the “how much material” side of a project; the cost side scales the same way. For larger structures like a deck, the concrete calculator handles the foundation volume, and the roofing cost calculator covers the surface above.