Lumber Board Foot Calculator

A board foot is the standard unit of measurement for lumber volume in North America. One board foot equals a piece of wood that is 1 inch thick, 12 inches wide, and 12 inches long — or equivalently, 144 cubic inches of wood.

The board foot formula: Board Feet = (Thickness in inches x Width in inches x Length in feet) / 12

Or equivalently: Board Feet = (Thickness x Width x Length in inches) / 144

Examples:

• A 1x12 board that is 8 feet long = (1 x 12 x 8) / 12 = 8 board feet
• A 2x4 that is 8 feet long = (2 x 4 x 8) / 12 = 5.33 board feet
• A 2x6 that is 10 feet long = (2 x 6 x 10) / 12 = 10 board feet
• A 4x4 that is 12 feet long = (4 x 4 x 12) / 12 = 16 board feet

Nominal vs actual dimensions: In the lumber industry, board foot calculations use nominal dimensions, not actual (dressed) dimensions. A “2x4” is actually 1.5 inches by 3.5 inches after milling and drying, but it is priced and measured as if it were 2 inches by 4 inches. This distinction is important because:

• Rough-sawn lumber (sold at sawmills) is measured at full nominal dimensions
• Dressed (surfaced) lumber from retail stores uses nominal dimensions for pricing even though the actual wood is smaller
• Hardwood lumber is often sold by the board foot at actual (random width) dimensions

Hardwood lumber grading and board feet: Hardwoods are sold differently than softwood construction lumber. Instead of fixed widths, hardwood boards come in random widths and lengths. They are graded by the National Hardwood Lumber Association (NHLA) as FAS (First and Seconds), Select, #1 Common, or #2 Common. The price per board foot varies dramatically by species, grade, and thickness:

• 4/4 (1-inch thick, pronounced “four-quarter”) is the standard starting thickness
• 5/4, 6/4, 8/4, 10/4, 12/4 represent thicker stock before surfacing
• 8/4 (2-inch thick) typically costs 30-50% more per board foot than 4/4 of the same species

Converting board feet to other units:

• 1 board foot = 144 cubic inches = 1/12 cubic foot = 0.00236 cubic meters
• 1 cubic foot = 12 board feet
• 1 cubic meter = 423.78 board feet
• 1 MBF (thousand board feet) is a common bulk purchase unit

Estimating project needs: Always add a waste factor to your board foot estimate. For straightforward projects with careful cutting, add 15-20%. For complex projects with many angles or curves, add 25-30%. Also account for defects in the lumber that may require cutting around knots, checks, or sapwood.

Weight estimation from board feet: Since wood density varies by species, board feet alone do not tell you the weight. However, you can estimate: Weight (lbs) = Board feet x (species density in lbs/ft3) / 12. For example, red oak at 44 lbs/ft3: 100 board feet weighs approximately 367 lbs (166 kg).