Board Foot Calculator

How to use the board foot calculator

This board foot calculator works the way lumber is bought: a list of sizes, each with a count. It adds up the board feet, the linear feet and the volume, and if you enter prices, the cost. Two more tabs convert board feet to linear feet for one size and estimate the lumber in a log. All of the math runs in your browser.

1. Pick the calculator. Lumber list for a shopping or cut list, Linear feet to convert one size between board feet and length, or Log scale for logs.
2. Enter each size once. Choose a quick size (a nominal softwood size such as 2 × 4, or a hardwood thickness such as 4/4 or 8/4), or type the thickness and width, then the length and how many pieces. Add a piece for every other size.
3. Set the options. Enter a waste allowance from your plan. Tick Count lumber under 1 in thick as 1 in if your supplier counts thin stock that way.
4. Add prices if you want a cost. Each row takes a price per board foot, per linear foot or meter, per piece or per cubic meter.
5. Read the results. Copy them, download the cut list as a CSV file for a spreadsheet, or print the results card.

Every measurement has its own unit, and you can type 5/4, 3 1/2, 19 mm or 8' 6". The calculator remembers your list on this device.

What is a board foot?

A board foot is the unit lumber is sold by in the United States. The USDA Forest Products Laboratory's Wood Handbook defines it as "a board 12 in. long, 12 in. wide, and 1 in. thick or its cubic equivalent" (FPL-GTR-282, glossary). That is 1 × 12 × 12 = 144 cubic inches, so a cubic foot of 1,728 cubic inches holds 12 board feet. A board foot is a volume, not a length or an area: a board 2 in thick has twice the board feet of a 1 in board of the same width and length.

The American Softwood Lumber Standard, published by the National Institute of Standards and Technology as PS 20-20, says how to count it: "The number of board feet in a piece of lumber is obtained by multiplying the nominal thickness in inches or fraction of an inch by the nominal width in feet by the length in feet." (PS 20-20 §2.2). Width in feet is width in inches ÷ 12, which is where the ÷ 12 in the formula below comes from.

How to calculate board feet

1. Measure the thickness and width in inches. Use the nominal size for softwood lumber sold as 2 × 4, 1 × 6 and so on, and the rough thickness for hardwood, such as 1 in for 4/4.
2. Measure the length in feet. Use the length of the piece you buy, not the length you will cut from it.
3. Multiply and divide by 12. Board feet = thickness × width × length ÷ 12. With the length in inches, divide by 144 instead.
4. Multiply by the number of pieces. Do this for each size, then add the sizes together.
5. Add the waste allowance. Multiply the total by 1 plus the waste percentage ÷ 100.
6. Price it. Multiply the board feet by the price per board foot, or the length by a price per linear foot, or the count by a price per piece.

board feet = thickness (in) × width (in) × length (ft) ÷ 12
           = thickness (in) × width (in) × length (in) ÷ 144
total      = Σ quantity × board feet of one piece
with waste = total × (1 + waste ÷ 100)

A 2 × 4 that is 8 ft long: 2 × 4 × 8 ÷ 12 = 5.33 board feet. All in inches, 2 × 4 × 96 ÷ 144 gives the same 5.33. Ten of them hold 53.33 board feet.

Board feet chart for common sizes

Board feet for one piece, counted on the nominal size for softwood and the rough thickness for hardwood, as the formula above gives them.

The calculator's example list is ten 2 × 4s 8 ft long, four 2 × 6s 12 ft long and three 4/4 boards 6 in wide and 8 ft long: 17 pieces and 113.33 board feet, or 124.67 with 10% for waste, in 152 linear feet of lumber.

Nominal vs actual size: which one counts?

Softwood lumber is named by its nominal size, which is larger than the board you take home. PS 20 calls the nominal size "The label designation for lumber size categories that does not reflect the dressed size" and gives the example that "a dry 2 by 4 is surfaced to 38.1 mm by 88.9 mm (1 1/2 by 3 1/2 inches)" (PS 20-20 §2.16). Board feet for dimension lumber and boards sold by nominal size are counted on the nominal size, because that is how the standard defines board measure (§2.2 above). The Wood Handbook says the same: "In practice, the board foot calculation for lumber 1 in. or more in thickness is based on its nominal thickness and width and the actual length."

So a 2 × 4 counts as 0.67 board feet per linear foot even though the wood in it, at 1 1/2 × 3 1/2 in, is 0.44. Lumber finished to a size that is not standard is counted, in the standard's words, "as of either the rough or the nominal size that was used in its manufacture" (PS 20-20 §4.2). When lumber is measured in cubic meters instead, PS 20 uses the dressed size.

Green (undried) lumber is dressed slightly larger; the table shows the dry sizes. The quick sizes in the calculator fill in the nominal size and show the dressed size beside it.

Hardwood lumber: 4/4, 5/4, 8/4 and quarters

Hardwood lumber, the Wood Handbook notes, "is usually manufactured to random width", and it is sold by the board foot, often rough. Its thickness is given in quarters of an inch: 4/4 ("four quarter") is 1 in, 5/4 is 1 1/4 in, 6/4 is 1 1/2 in, 8/4 is 2 in, 12/4 is 3 in and 16/4 is 4 in. The board feet are counted on that rough thickness and the board's measured width: a 4/4 board 6 in wide and 8 ft long is 4 board feet, and an 8/4 board 8 in wide and 10 ft long is 13.33.

Most hardwood lumber bought in North America is graded under the rules of the National Hardwood Lumber Association (NHLA), Purdue Extension notes, and the Wood Handbook says those rules "are considered standard in grading hardwood". Graders also use surface measure, the face area in square feet; Purdue Extension describes it as "the width of the board in inches and fractions multiplied by the length in whole feet divided by 12", with fractions rounded to the nearest whole number (FNR-130). A yard that tallies this way can round each board, so its total may differ a little from the exact figure the calculator gives.

For lumber thinner than 1 in, the Wood Handbook notes that "Lumber with a nominal thickness of less than 1 in. is calculated as 1 in." The calculator counts the thickness you enter unless you tick Count lumber under 1 in thick as 1 in.

Board feet to linear feet, and back

Linear feet are only length. For one thickness and width, every linear foot holds the same number of board feet, thickness × width ÷ 12, so converting is a single multiplication or division:

board feet per linear foot = thickness (in) × width (in) ÷ 12
linear feet = board feet × 12 ÷ (thickness × width)
board feet  = linear feet × thickness × width ÷ 12

100 board feet of 1 × 6 is 100 × 12 ÷ 6 = 200 linear feet. 150 linear feet of 2 × 6 is 150 board feet, because a 2 × 6 holds exactly 1 board foot per linear foot. Prices convert the same way: a price per linear foot is the price per board foot × thickness × width ÷ 12, so for a 1 × 6 it is half the board-foot price and for a 2 × 12 twice it. The Linear feet tab does both.

Board feet, cubic feet and cubic meters

Because a board foot is 144 cubic inches and NIST defines a cubic inch as exactly 16.387064 cubic centimeters, one board foot is exactly 0.002359737216 cubic meters, and one cubic meter is about 423.776 board feet. A cubic foot is 12 board feet, so board feet ÷ 12 gives cubic feet.

The example list of 113.33 board feet is 9.44 cubic feet or 0.267 cubic meters. These are the volume of the sizes entered (nominal for softwood), not of the dressed wood.

How much extra lumber to buy

There is no single waste figure: it depends on the grade, how well your cut list fits the lengths you buy, knots, splits, warp and mistakes. Rough hardwood also gets thinner and narrower when it is surfaced, as the hardwood table above shows. Enter the allowance from your plan or your own experience; the calculator multiplies the board feet and the cost by 1 plus that percentage ÷ 100. The example list's 10% turns 113.33 board feet into 124.67.

Lumber cost: price per board foot, linear foot or piece

Lumber may be priced per board foot (or per thousand board feet, MBF), per linear foot or per piece, depending on the product and the seller. Each row in the list takes its own price and basis, so you can mix them:

• Per board foot: cost = quantity × board feet of one piece × price.
• Per linear foot or meter: cost = quantity × length × price.
• Per piece: cost = quantity × price.
• Per cubic meter: cost = board feet × 0.002359737216 × price.

The total adds up only the rows you priced, and the waste allowance is applied to it too. Nothing is filled in for you, because prices change with species, grade, dryness, the yard and the region. Delivery, milling and tax are not included.

Board feet in a log: Doyle, Scribner and International 1/4-inch

A log rule estimates how many board feet of lumber a sawmill could cut from a log, from its small-end diameter inside the bark (D, in inches) and its length (L, in feet). Purdue Extension's Log and Tree Scaling Techniques (FNR-191) notes that of the many rules ever published "only three, Doyle, Scribner, and International, are widely recognized and in current use", and reminds readers that "log and tree scaling are just estimates of the final board footage expected". The calculator uses the formulas it gives:

Doyle          = (D − 4)² × L ÷ 16
Scribner       = (0.79 D² − 2 D − 4) × L ÷ 16        (Bruce and Schumacher, 1950)
International  = 0.04976191 L D² + 0.006220239 L² D − 0.1854762 L D
 1/4-inch        + 0.0002591767 L³ − 0.01159226 L² + 0.04222222 L   (Grosenbaugh, 1952)

For a log 16 in across the small end and 16 ft long, Doyle gives 144 board feet, the Scribner formula 166 and the International 1/4-inch rule 180. FNR-191 explains that Doyle's allowance for slabs and edgings "seriously under scales small logs and over scales large logs": a 10 in log 12 ft long is 27 board feet by Doyle but 45 by the International rule. Scribner Decimal C tables round to the nearest 10 board feet and the International rule to the nearest 5, which the calculator does for the International rule too.

Which rule applies is decided where the log is bought or sold, so ask before you compare offers. Measure the small end inside the bark twice at right angles and average the two, and scale a log longer than 20 ft as two or more logs. None of the rules measures the wood in the log itself, and the lumber a mill actually gets depends on the log, the saw and the sawyer.

Metric lumber

Switch Units to Metric to see lengths in meters and volumes in cubic meters first; new rows start in millimeters and meters. Each field also has its own unit, so you can mix them. The calculator converts everything to inches and feet first, using the exact definitions: 25.4 millimeters to the inch and 0.3048 meters to the foot. Where lumber is sold by the cubic meter, enter the price per cubic meter, or use the volume the results show.

How we calculate

Every figure in the tool and on this page comes from the same code, and the examples above are checked against it automatically.

• Units. Thickness and width are converted to inches (millimeters ÷ 25.4) and lengths to feet (meters ÷ 0.3048), the exact NIST definitions.
• One piece. Board feet = thickness × width × length ÷ 12, with nothing rounded. Optionally a thickness under 1 in is counted as 1 in.
• The list. Board feet = Σ quantity × board feet per piece; linear feet = Σ quantity × length; with waste = total × (1 + waste ÷ 100); cubic feet = board feet ÷ 12; cubic meters = board feet × 0.002359737216.
• Converter. Linear feet = board feet × 12 ÷ (thickness × width); price per linear foot = price per board foot × thickness × width ÷ 12.
• Logs. The three formulas above for one log, Doyle and Scribner to the nearest board foot and International to the nearest 5, times the number of logs.
• Cost. Each row's quantity × your price on its basis; the total is the sum of the priced rows. Nothing is filled in for you.

The calculator does not grade lumber, pick a species or size for a job, check spans or loads, or round the tally the way a lumber yard or a grader may.

Your list stays on your device

The calculator runs entirely as JavaScript in your browser tab. Nothing you enter is uploaded: the page's Content-Security-Policy allows connections only back to this site, and the tool has no code that sends anything anywhere. It remembers your last list and settings in your browser's local storage, on your device only. There is no account and no cookie.

Sources

• NIST: Voluntary Product Standard PS 20-20, American Softwood Lumber Standard: §2.2 board measure, §2.5 cubic measurement, §2.16 nominal size, §4.1–4.2 tally, and Table 3, nominal and minimum dressed sizes.
• USDA Forest Service, Forest Products Laboratory: Wood Handbook, Wood as an Engineering Material (FPL-GTR-282, 2021): the glossary entry for the board foot, and Chapter 6, Commercial Lumber, Round Timbers, and Ties, with Table 6–4, standard thicknesses of rough and surfaced hardwood lumber.
• Purdue University Cooperative Extension Service: Log and Tree Scaling Techniques (FNR-191), Daniel Cassens: the Doyle, Scribner and International 1/4-inch log rules, their formulas and tables.
• Purdue University Cooperative Extension Service: Quality Control in Lumber Purchasing: Hardwood Lumber Grades (FNR-130), Daniel Cassens: an overview of the NHLA hardwood grading rules and surface measure.
• National Institute of Standards and Technology: NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement: 1 inch = 2.54 centimeters, 1 foot = 0.3048 meter and 1 cubic inch = 16.387064 cubic centimeters, exactly.

Reviewed by microplugins · Last updated October 2026

This is an educational tool, not professional lumber-grading, forestry, engineering or construction advice. It counts lumber; it does not choose sizes, grades or species for a job. Lumber yards, mills and graders may measure and round differently, so check their tally and their log rule before you pay.