Lumber Board Feet Calculator
Estimate lumber board feet for your project with our free calculator. Get accurate material quantities, costs, and specifications.
Formula
Board Feet = Thickness (in) x Width (in) x Length (ft) / 12
One board foot equals 144 cubic inches of wood, or a piece 1 inch thick, 12 inches wide, and 1 foot long. Multiply the nominal thickness in inches by the nominal width in inches by the length in feet, then divide by 12.
Frequently Asked Questions
What is a board foot and how is it calculated?
A board foot is a unit of volume used to measure lumber, equal to a piece of wood 1 inch thick, 12 inches wide, and 12 inches long (144 cubic inches or 1/12 of a cubic foot). The formula is: Board Feet = Thickness (inches) x Width (inches) x Length (feet) / 12. For example, a 2x6 board that is 8 feet long equals 2 x 6 x 8 / 12 = 8 board feet. This measurement uses nominal dimensions (the stated size before planing), not actual dimensions, which is an important distinction when calculating lumber quantities.
What is the difference between nominal and actual lumber dimensions?
Nominal dimensions are the stated size of lumber (like 2x4), while actual dimensions are the true measurements after drying and planing. A nominal 2x4 actually measures 1.5 x 3.5 inches, and a 2x6 measures 1.5 x 5.5 inches. For board foot calculations, the lumber industry standard is to use nominal dimensions, which means you pay for more wood than you actually receive. This is why hardwood lumber sold by the board foot is measured differently, using actual thickness in quarter-inch increments (4/4, 5/4, 6/4, 8/4) and actual width.
How much does lumber cost per board foot?
Lumber prices per board foot vary dramatically by species, grade, and market conditions. Pressure-treated southern pine ranges from $1.50 to $3.00 per board foot. Construction-grade Douglas fir runs $2 to $4 per board foot. Hardwood prices are higher: red oak averages $4 to $7 per board foot, hard maple $5 to $8, cherry $6 to $10, and black walnut $8 to $15 per board foot. Premium figured or wide boards command significant premiums. Prices also vary by lumber yard, with specialty hardwood dealers often being more expensive but offering better selection and quality.
How do I calculate board feet for rough-sawn hardwood lumber?
Rough-sawn hardwood lumber is sold by the board foot using actual measurements rather than nominal sizes. Thickness is stated in quarters of an inch: 4/4 means 1 inch thick, 5/4 is 1.25 inches, 6/4 is 1.5 inches, and 8/4 is 2 inches thick. Width is the actual measurement of each board, and length is rounded down to the nearest foot. The formula remains the same: Thickness x Width x Length / 12. Because rough lumber varies in width, each board must be measured individually or estimated using the average width. Many hardwood dealers sell random widths and lengths in bundles.
How many board feet are in common framing lumber sizes?
Here are board feet per linear foot for common framing sizes: a 2x4 is 0.667 BF per foot, a 2x6 is 1.0 BF per foot, a 2x8 is 1.333 BF per foot, a 2x10 is 1.667 BF per foot, and a 2x12 is 2.0 BF per foot. So a standard 8-foot 2x4 contains 5.33 board feet, and a 12-foot 2x10 contains 20 board feet. For posts, a 4x4 is 1.333 BF per foot and a 6x6 is 3.0 BF per foot. Knowing these values helps quickly estimate lumber needs on job sites without a calculator.
How do I interpret the result?
Results are displayed with a label and unit to help you understand the output. Many calculators include a short explanation or classification below the result (for example, a BMI category or risk level). Refer to the worked examples section on this page for real-world context.