Board Foot Calculator

How to use this board foot calculator

1. Enter the thickness and width in inches. For standard softwood lumber, use the nominal size (2 and 6 for a 2 × 6).
2. Enter the length in feet or inches.
3. Enter how many pieces of that size you need.
4. Optionally, enter your lumber yard's price per board foot to see a total.
5. For a mixed order, run each size separately and add the board feet.

How to calculate board feet: the formula, shown

A board foot is the unit lumber is sold and tallied in. The American Softwood Lumber Standard (PS 20) defines it: multiply the nominal thickness in inches by the nominal width in feet by the length in feet. With width in inches, that is thickness × width × length ÷ 12. One board foot is the same as a piece 1 in thick, 12 in wide, and 1 ft long.

Default example. Ten 2 × 6 boards, 8 ft long, using nominal sizes. Change the inputs above and the result panel recalculates; this worked example always shows the default.

Per piece   = 2 in × 6 in × 8 ft ÷ 12 = 8 bd ft
Total       = 8 bd ft × 10 pieces = 80 bd ft
Linear feet = 8 ft × 10 = 80 ft
Cost        = total bd ft × your price per bd ft (enter a price to see it)

PS 20 notes that a board foot “is not a well-defined unit of volume”: because it is based on nominal dimensions, it does not equal the wood's actual dressed volume. Use it for buying and pricing, not to calculate weight.

Board feet chart for common lumber sizes

Board feet per piece for common nominal lumber sizes and lengths, computed with the PS 20 formula.

Board feet per linear foot = thickness × width ÷ 12. Multiply by the number of pieces for a total.

Quick answers: board feet in common lumber sizes

Each answer is computed with the same formula as the calculator, using its default settings unless the question says otherwise.

Buying lumber by the board foot

The default ten 2 × 6 × 8 ft boards come to 80 board feet. Hardwood and specialty lumber is usually priced per board foot; dimensional lumber at home centers is usually priced per piece. Board feet let you compare the two.

• Large orders are often quoted per thousand board feet (MBF). Divide total board feet by 1,000.
• Add extra pieces for defects, cuts, and mistakes; how many depends on the grade and the job.
• For deck surfaces, the deck calculator counts boards from the deck size, board width, and gap.

Nominal vs. actual lumber sizes

A “2 × 6” is a nominal size. After drying and planing, PS 20 lists the minimum dressed (dry) size of a nominal 6 in width as 5-1/2 in, and a nominal 2 in thickness as 1-1/2 in. Board feet for standard softwood lumber are still figured on the nominal size, which is why the calculator asks for nominal dimensions. For actual sizes of other common lumber, see the nominal vs. actual lumber size chart.

Rough-sawn and nonstandard lumber

For lumber finished to nonstandard sizes, PS 20 says it is tallied by board measure using the rough or nominal size it was made from. Hardwood and rough-sawn sellers may use their own conventions, so ask how your yard measures before comparing prices.

Tips for estimating lumber

• Check whether your supplier prices by the board foot, the linear foot, or the piece before comparing quotes.
• Board feet don't tell you weight. Wood density varies by species and moisture.
• When ordering a mixed list, write each size and length on its own line, then total the board feet.
• For trim and boards sold by length, the linear-feet figure is often what you need.

Board foot calculator FAQ

Related calculators and guides

Sources

• Voluntary Product Standard PS 20-25, American Softwood Lumber Standard: definition of board measure — National Institute of Standards and Technology. Used for: Board feet = nominal thickness (in) × nominal width (ft) × length (ft). Checked 2026-10-05.