Lumber Board Feet Calculator
Enter the thickness, width, and length of a board, and how many you have, to find the total board feet.
How board feet are calculated
A board foot is a volume measurement used for lumber in the US, equal to a board 1 inch thick, 12 inches wide, and 12 inches long (144 cubic inches). The formula is: board feet = (thickness in inches × width in inches × length in feet) / 12.
Board feet measures volume, not just surface area, which is why thickness matters — a thicker board has more board feet for the same width and length, since it contains more wood.
Frequently asked questions
Why divide by 12 in the board feet formula?
The formula multiplies thickness and width in inches by length in feet; dividing by 12 converts the result into the standard board-foot unit, which is defined using a 1-inch by 12-inch by 12-inch (1 foot) reference board.
Is a board foot the same as a square foot?
No — a square foot measures area (no thickness involved), while a board foot measures volume and includes the board's thickness, which is why lumber pricing by board foot accounts for both thickness and size.
How do I calculate board feet for multiple boards of the same size?
Calculate the board feet for one board, then multiply by the quantity — this calculator does that for you automatically.