Updated · Built and checked by the PlinzoTools team, formulas tested against published sources
Calculate board feet -- the standard lumber-industry volume unit -- from thickness, width, and length.
A board foot is the standard unit lumber yards use to price and measure hardwood and specialty lumber -- it's the volume of a board that's 1 inch thick, 12 inches wide, and 1 foot long. Unlike a linear foot (which only measures length and ignores thickness or width), a board foot accounts for all three dimensions, which is why it's the unit that actually reflects how much wood you're buying.
Enter your board's thickness and width in inches and its length in feet, plus a quantity if you're buying several identical boards. The result shows board feet per board and the total across your full order.
Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12
Dividing by 12 converts the result into the standard board-foot unit (since a true 1in x 12in x 1ft board equals exactly 1 board foot by definition, and the formula scales proportionally from there).
Board feet is most relevant for hardwood, specialty, and rough-sawn lumber, which is priced per board foot at most lumber yards -- softwood dimensional lumber (like standard construction 2x4s) is more often priced per linear foot or per piece instead, which is what the Lumber Calculator handles.
This is the most common source of confusion. Lumber is often labeled by a nominal size that is larger than the true size after milling. A softwood board sold as 2 x 6 is really smaller in both directions. Hardwood is often sold by the quarter, such as 4/4 for about one inch thick in the rough. Lumber yards may calculate board feet using the nominal or rough size, so ask which they use, and enter the dimensions that match the way you will be billed.
Suppose a hypothetical tabletop uses four boards each 1 inch thick, 7 inches wide, and 6 feet long. Each board is 1 x 7 x 6 divided by 12, which is 3.5 board feet. Four boards total 14 board feet. If the yard charges a price per board foot, multiply the total by that price to get the estimated cost. Keep in mind you should buy more than the finished size, to allow for cutting away defects.
Many woodworkers plan for a noticeable margin over the finished size, and the right amount depends on species, grade, and the design, so ask the yard or a woodworker you trust.
Yards may round the length up or use the actual length of each board as it comes off the rack. Some round the width down to the nearest whole inch, and some apply minimum board-foot charges. If the price seems off, ask how they measure and round, and use their method in the calculator.
One board foot equals 144 cubic inches, or 1/12 of a cubic foot. So 12 board feet is one cubic foot of wood. This helps when comparing lumber pricing against other materials sold by cubic volume, or when estimating weight from species density figures you get from a reliable reference.
A board foot is the volume of a board 1 inch thick, 12 inches wide, and 1 foot long -- the standard unit lumber yards use to measure and price hardwood and specialty lumber.
A linear foot only measures length, ignoring thickness and width. A board foot accounts for all three dimensions, so it reflects the actual volume of wood, not just how long the board is.
No -- hardwoods and specialty lumber typically are, but standard softwood dimensional lumber (2x4s, 2x6s) is usually priced per linear foot or per piece instead.
Using nominal sizes, 2 x 4 x 8 divided by 12 gives about 5.33 board feet. Softwood 2x4s are usually priced per piece, so this is mostly useful for comparison.
Use whichever the seller uses to bill. For hardwood, that is often the rough thickness and width. Ask the yard if you are unsure.
Twelve. A board foot is 144 cubic inches, and a cubic foot has 1,728 cubic inches.