How it works
One board foot is 144 cubic inches: 1 in thick × 12 in wide × 12 in long. Board feet per piece = thickness in inches × width in inches × length in feet ÷ 12, which is the same as thickness × width × length in inches ÷ 144.
Total board feet = board feet per piece × quantity. If you enter a price per board foot, cost = total board feet × your price. No price is assumed.
Worked example
One 2 × 6 in board, 8 ft long: 2 × 6 × 8 ÷ 12 = 8 board feet. In inches: 2 × 6 × 96 ÷ 144 = 8.
Ten of the same boards would be 80 board feet.
Tips and common mistakes
Nominal and actual sizes
Lumber is named by nominal size, such as 2 × 6 or 4 × 4, but the dried and planed board measures less. For example, the actual side of a nominal 4 × 4 post is listed here as 3.5 in, and a nominal 6 in deck board as 5.5 in wide., from the Southern Pine Inspection Bureau.
Use the “Sizes entered as” selector to record which sizes you used. The math is the same either way; nominal and actual inputs simply give different board-foot totals. Ask your supplier which sizes its board-foot price uses.
- Enter length in feet or inches; the calculator converts it.
- Quantity must be a whole number of pieces.
- Price is per board foot, not per piece or per linear foot.
Questions about this calculator
What is a board foot?
A board foot is a piece of wood 12 in wide, 12 in long and 1 in thick, which is 144 cubic inches (University of Wisconsin–Madison Extension).
How do you calculate a board foot?
Board feet = thickness (in) × width (in) × length (ft) ÷ 12. If the length is in inches, divide by 144 instead.
How many board feet is a 2x4x8?
2 × 4 × 8 ÷ 12 = 5.33 board feet using nominal sizes, which is how lumber is usually sold. Using actual sizes (1.5 × 3.5 in), it is 3.5 board feet.
How many board feet is a 2x6x10?
2 × 6 × 10 ÷ 12 = 10 board feet, nominal.
How many board feet are in a 1x12x12?
1 × 12 × 12 ÷ 12 = 12 board feet, nominal.
Sources
Values marked with a link come from the linked source, which opens in a new tab. Unit conversions and our own defaults are listed separately. Every value the site uses is in the methodology source register.
Where the numbers come from 4
- Cubic inches per board foot
- 144 cu in/board ft
- University of Wisconsin–Madison Extension, Forestry Facts No. 42, What Is A Board Foot? (opens in a new tab)forestry.extension.wisc.edu · PDF
- Meters per international foot
- 0.3048 m/ft
- NIST, international foot conversion (opens in a new tab)nist.gov
- Actual side of a nominal 4 × 4 post
- 3.5 in
- Southern Pine Inspection Bureau, Nominal vs actual lumber sizes (cites PS 20-20) (opens in a new tab)blog.spib.org
- Editable deck board actual width default
- 5.5 in
- Southern Pine Inspection Bureau, Nominal vs actual lumber sizes (cites PS 20-20) (opens in a new tab)blog.spib.org
Unit conversions and our defaults4
- Inches per foot
- 12 in/ft
- Unit definition: one foot contains twelve inches
- Cubic inches per cubic foot
- 1728 cu in/cu ft
- Geometry: 12 × 12 × 12 inches
- Centimeters per meter
- 100 cm/m
- Metric prefix definition: centi is one hundredth
- Board foot calculator starting piece
- 2, 6, 8 in thickness, in width, ft length
- Owner worked example; editable starting measurements