About Lumber Calculator
Board feet is the standard unit of measurement for lumber in North America. One board foot equals a piece 12" x 12" x 1" thick. The formula is: (Thickness × Width × Length in inches) ÷ 144.
Use this calculator for dimensional lumber (2x4, 2x6, etc.), hardwood, or any sawn lumber. Remember that nominal sizes (e.g. 2x4) differ from actual sizes (1.5" x 3.5").
When to Use This Calculator
Building a deck: A 12x16 ft deck using 2x6 decking boards (actual 1.5x5.5) spaced with 1/8 inch gaps needs roughly 35 boards at 16 ft each. That's over 500 board feet of lumber — knowing this helps you budget before you visit the lumber yard.
Framing a shed: A 10x12 ft shed requires studs, joists, rafters, and headers. Using this calculator per lumber size helps you total the material cost. The wall framing alone (2x4 studs at 16-inch spacing) needs about 30 studs.
Buying hardwood for furniture: Building a dining table from oak? A 6 ft table that's 3 ft wide needs roughly 18 board feet of 4/4 (1-inch thick) oak, plus extra for legs and aprons. At $6-8 per board foot for good oak, that's over $150 just in lumber.
How to Use the Lumber Calculator
Suppose you're building a deck and need to order ten 2x6 boards that are 8 ft long. But remember: a "2x6" isn't actually 2 by 6 inches — its actual size is 1.5 by 5.5 inches. Enter thickness 1.5, width 5.5, length 96 (inches), quantity 10. If the price per board foot is $2.50, click calculate. You'll see each board is 5.5 board feet, so your total is 55 board feet, costing $137.50. This is how lumber yards and home centers actually charge you, so knowing board feet helps you compare prices between suppliers. Hardwood lumber (oak, maple, walnut) is almost always sold by the board foot, while construction lumber (2x4s, 2x6s) is often sold per linear foot — but converting to board feet helps you compare apples to apples.
Tips for Buying Lumber
Always account for the difference between nominal and actual dimensions. A 2x4 is actually 1.5x3.5 inches, a 1x6 is 0.75x5.5 inches. When calculating board feet, use the actual dimensions, not the nominal ones, or you'll overestimate by 15-25%. Buy your lumber in person if possible — "select" or "clear" grade costs more but has fewer knots and defects. For construction projects, #2 grade is usually fine and much cheaper. Let the lumber acclimate in your workspace for at least 48 hours before cutting to prevent warping. And always buy 10-15% extra for mistakes, test cuts, and grain matching.