Quickly estimate lumber volume and cost for your construction and woodworking projects.
To find the board footage of a piece of lumber, multiply its thickness in inches by its width in inches, then multiply by its length in feet, and divide the result by 12. For multiple pieces, multiply this result by the total quantity. If using metric inputs, dimensions are converted to imperial equivalents (1 inch = 2.54 cm, 1 foot = 0.3048 m) to compute the standardized board feet volume.
Formula source: AWC (American Wood Council) NDS and SPIB grading rules.
A board foot is a specialized unit of volume used in the United States and Canada for measuring rough lumber. One board foot represents the volume of a board that is 12 inches wide, 12 inches long, and 1 inch thick, which equals 144 cubic inches. To calculate the board footage of any piece of wood, you use the standard formula: Board Feet = (Thickness in inches × Width in inches × Length in feet) / 12.
When dealing with rough-sawn lumber, particularly hardwoods, thickness is often expressed in quarters of an inch. For example, a 1-inch thick board is referred to as "four-quarter" (4/4), while a 2-inch thick board is "eight-quarter" (8/4). It is important to note that softwood lumber is typically sold by nominal dimensions (the size before planing, such as a 2x4), whereas hardwood lumber is often measured by its actual rough dimensions before surfacing. Always clarify with your supplier whether they are billing based on nominal or actual dimensions.
Several critical factors influence the final yield and cost of lumber in construction and woodworking projects. First and foremost is the lumber grade. Hardwoods graded by the National Hardwood Lumber Association (NHLA) range from FAS (First and Seconds), which offers the highest yield of clear cuttings, down to Common grades that contain more knots and defects. Choosing a lower grade may reduce the initial price per board foot but will significantly increase your waste factor.
Milling and drying also play a massive role in pricing. Kiln-dried lumber is more stable but carries a premium over green or air-dried lumber due to the energy costs of running dry kilns. When planning a purchase, always factor in a waste allowance. For standard projects using high-grade lumber, a 10% to 15% waste factor is typical. However, if you are working with lower-grade wood or require highly specific grain matching, you should increase your waste estimate to 20% or even 30% to avoid running short mid-project.