How to Calculate Board Footage

Measurement Standards

The lumber grading standards used in the U.S. hardwood industry are based on the imperial system, using inches and feet, whereas most international markets are more familiar with the metric system. Additionally, the grading rules were designed with random width and length lumber in mind. For specific requirements, it's important to discuss them before placing an order.

Board Foot Calculation

• A board foot (BF) is the primary unit of measurement for hardwood lumber.
• One board foot is defined as a board measuring 1 foot in length, 1 foot in width, and 1 inch in thickness. (1 foot = 0.305 meters, 1 inch = 25.4mm)
• The formula for calculating board feet is:
  W (width in inches) ×L (length in feet) ×D (thickness in inches) ÷12=BF
• The percentages of clear wood required for each grade are based on this 12-foot measurement standard.

Surface Measure

Surface measure (SM) refers to the total surface area of a board in square feet. To calculate the surface measure, multiply the board’s width in inches by its length in feet and divide the result by 12, rounding to the nearest whole number. The required percentage of clear wood for each grade is based on surface measure rather than board feet, meaning all boards, regardless of thickness, are graded consistently.

Example Calculation for Surface Measure and Board Feet

For a board that is 2 inches thick, 6 1/4 inches wide, and 8 feet long:

When preparing a tally for export, boards are recorded by their width and length. Widths are rounded to the nearest whole inch, and lengths are rounded to the nearest whole foot.

For example, a board with a width of 5 1/4" and a length of 8 1/2' would be recorded as 5" and 8'.

Standard Thickness for Rough Sawn Lumber

Rough sawn lumber thickness is commonly expressed in quarters of an inch, such as 1" being referred to as 4/4. The majority of U.S. hardwood lumber is sawn between 1" and 2", with other thicknesses available in smaller quantities. The standard thicknesses and their metric equivalents are as follows:

Kiln-Dried Lumber Measurement

• Net tally: The actual board feet of lumber after the kiln drying process.
• Gross tally (Green tally): The board feet of lumber before kiln drying. Typically, kiln dried lumber will be approximately 7% less than the gross tally due to shrinkage during drying.

Estimating Board Feet in a Bundle

To estimate the board feet in a bundle, first calculate the surface measure of one layer of boards. Multiply the width (after accounting for gaps) by the length of the layer and divide by 12. For bundles with multiple lengths, use the average length. Multiply the result by the total number of layers in the bundle.

Example Calculation for Bundle Estimation

Average width of 40" x 8' (lumber only, accounting for gaps between the boards) and length of 8')

Surface measure for one layer:
40" × 8′ = 320 ÷ 12 = 26.67"

Board feet for one layer (multiply SM by thickness)
26.67 × 2" = 53.34

For a bundle with 10 layers, the total board feet is:
53.34 × 10 = 533.4

Estimated board feet in the bundle = 533

Conversion Factors

• 1” = 25.4 millimeter (mm)
• 1 meter = 3.281 feet
• 1,000 BF = 2.36 cubic meters (m³)
• 1 m³ = 424 board feet (BF)
• 1 m³ = 35.315 cubic feet (cu.ft)