Lumber Board Feet Calculator
Calculate the board footage of any lumber piece to estimate material costs and quantities. Use it when buying or selling dimensional lumber at the lumberyard.
About this calculator
A board foot is the standard unit of volume used to price and measure hardwood and softwood lumber. It represents a piece of wood that is 1 inch thick, 12 inches wide, and 12 inches long — equivalent to 144 cubic inches. The formula is: Board Feet = (Thickness × Width × Length) / 144, where thickness and width are in inches and length is in feet. This conversion divides the total cubic inches by 144 to yield board feet. For example, a thicker or wider plank will yield more board feet and cost proportionally more. Understanding board feet helps contractors, woodworkers, and homeowners compare lumber prices accurately regardless of the board's physical dimensions.
How to use
Suppose you have a plank that is 2 inches thick, 6 inches wide, and 10 feet long. Plug the values into the formula: Board Feet = (2 × 6 × 10) / 144 = 120 / 144 ≈ 0.833 board feet per plank. If you need 20 such planks, multiply: 0.833 × 20 = 16.67 board feet total. At a price of $5 per board foot, your lumber cost would be approximately $83.35. This quick calculation prevents over-ordering and helps you budget accurately before heading to the lumber yard.
Frequently asked questions
What is a board foot and how is it different from a linear foot?
A board foot is a unit of volume equal to 144 cubic inches, typically a 1-inch-thick, 12-inch-wide, 12-inch-long piece of wood. A linear foot simply measures length with no regard for thickness or width. Lumber yards price hardwoods in board feet because thickness and width both affect the material cost, whereas softwood dimensional lumber (like 2×4s) is often sold by the linear foot at a fixed size. When comparing prices, always confirm which unit is being used to avoid costly mistakes.
How do I calculate board feet for lumber that is less than 1 inch thick?
For lumber thinner than 1 inch, you still use the same formula: (Thickness × Width × Length) / 144. For instance, a ¾-inch-thick board 6 inches wide and 8 feet long equals (0.75 × 6 × 8) / 144 = 0.25 board feet. However, many hardwood dealers round up thickness to the nearest quarter-inch increment and may charge a minimum of 1 inch for very thin stock. Always verify the pricing convention with your supplier when working with thin or resawn lumber.
Why do I need to add a waste allowance when ordering lumber by board feet?
Cutting, planing, and jointing lumber always results in some material loss — typically 15–25% for rough-cut hardwoods and around 10% for dimensional softwoods. Defects like knots, warping, or end-checking also reduce usable yield. Adding a waste factor ensures you do not run short mid-project and need to make an extra trip or wait for a reorder. A common rule of thumb is to multiply your calculated board footage by 1.15 to 1.25 before placing your order.