Lumber Calculator
Calculate board feet and total lumber needed for your project based on dimensions and quantity.
Results
10 piece(s) of 2" x 4" x 8' lumber equals 53.33 board feet. Estimated cost at $5/board foot is $266.67.
How to Use This Calculator
Select the lumber dimensions from standard sizes such as 2x4, 2x6, 2x8, 2x10, or 2x12. Enter the length of each board in feet. Enter the number of pieces needed. The calculator computes the total board feet, which is the standard unit for purchasing lumber. Board feet equals the nominal thickness in inches multiplied by the nominal width in inches multiplied by the length in feet, divided by 12. For example, ten 2x6 boards at 8 feet each equals 80 board feet. The calculator also provides the total linear feet, estimated weight based on species, and an approximate cost using the price per board foot that you enter.
Understanding the Concept
Board feet is the standard measurement for buying and selling lumber in the United States. One board foot equals a piece of wood 1 inch thick, 12 inches wide, and 12 inches long, or 144 cubic inches. Lumber is sold at nominal dimensions, which are larger than the actual dimensions after surfacing. A nominal 2x4 actually measures 1.5 by 3.5 inches, and a 2x6 measures 1.5 by 5.5 inches. Despite the difference between nominal and actual sizes, board feet calculations always use nominal dimensions. This matters because pricing is based on board feet, and confusion between nominal and actual dimensions is a common source of estimation errors. Lumber species and grade also affect pricing and structural capacity. Southern Yellow Pine and Douglas Fir are the most common structural framing species in the US. Treated lumber is required for ground contact and exterior applications. Always verify species, grade, and treatment with the project specifications before ordering. Waste factor for framing projects is typically 10 to 15% to account for cuts, defects, and site damage.
The Formula Explained
Board feet equals the nominal thickness in inches multiplied by the nominal width in inches multiplied by the length in feet, all divided by 12. The formula is BF = (T multiplied by W multiplied by L) divided by 12, where T is thickness in inches, W is width in inches, and L is length in feet. For multiple pieces, multiply by the quantity: Total BF = BF per piece multiplied by the number of pieces. For example, a 2x8 that is 12 feet long contains (2 multiplied by 8 multiplied by 12) divided by 12 = 16 board feet. Twenty of these boards equal 320 board feet. Total linear feet is simply the length multiplied by the quantity. Add 10 to 15% waste factor to the total for framing projects.
Frequently Asked Questions
What is a board foot of lumber?
A board foot is a unit of volume equal to a piece of wood 1 inch thick, 12 inches wide, and 1 foot long. It equals 144 cubic inches. Board feet is the standard purchasing unit for lumber in the US. Calculations use nominal dimensions, not the smaller actual dimensions.
How many board feet are in a 2x4x8?
A single 2x4 that is 8 feet long contains 5.33 board feet, calculated as (2 multiplied by 4 multiplied by 8) divided by 12. Note that board foot calculations always use the nominal dimensions, not the actual 1.5 by 3.5 inch milled size.
What is the difference between nominal and actual lumber sizes?
Nominal size is the rough sawn dimension before surfacing. Actual size is the finished dimension after planing. A nominal 2x4 is actually 1.5 by 3.5 inches. A nominal 2x6 is 1.5 by 5.5 inches. Board feet and pricing are based on nominal dimensions.
How much waste should I add to a lumber estimate?
Add 10% for straightforward framing projects with standard lengths. Add 15% for projects with many cuts, angles, or non standard lengths. For finish carpentry and trim work, add 15 to 20% because appearance defects and precise fitting generate more waste.
How do I convert linear feet to board feet?
Multiply the linear feet by the nominal thickness and width in inches, then divide by 12. For example, 100 linear feet of 2x6 equals (2 multiplied by 6 multiplied by 100) divided by 12, which is 100 board feet.