Board foot calculator for lumber

Enter the pieces, thickness, width and length of each lumber size. Get the board feet for each and in total, the linear footage, the dressed size you will actually get, and the cost at your yard's price per board foot.

144 cu in.In one board foot

3 sizesIn one order

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Board feet

120

120 linear ft of lumber

120Linear feet

10Cubic feet (nominal)

Add a priceCost

Dressed sizes are the minimum dry sizes in the American Softwood Lumber Standard. Hardwood can come rough or surfaced, so measure what you buy.

Free. Your numbers become an estimate you can send from your phone.

How we got this

FormulaBoard feet = pieces × thickness (in.) × width (in.) × length (ft) ÷ 12A board foot is 144 cubic inches: 1 in. thick, 12 in. wide and 1 ft long (Minnesota Statutes 239.33). Softwood is tallied on its nominal size, not the smaller dressed size (PS 20-10, 2.2).
Item 110 × 2 in. × 6 in. × 12 ft ÷ 12 = 120 board feet
Total120 board feet

Size	Pieces	Bf each	Bf total	Dressed size
2 × 6 × 12 ft	10	12	120	1.5 × 5.5 in.
Total			120

Sources: Minnesota Statutes 239.33 (a board foot is 144 cubic inches); NIST Voluntary Product Standard PS 20-10, American Softwood Lumber Standard (board measure, Table 3 dressed sizes). Checked 2026-10-08.

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Key takeaways

Board feet = thickness (in.) × width (in.) × length (ft) ÷ 12, times the number of pieces. One board foot is 144 cubic inches: 1 in. × 12 in. × 1 ft.
Softwood is tallied on its nominal size. A 2x6 counts as 2 × 6 even though it is dressed to 1 1/2 × 5 1/2 in. (American Softwood Lumber Standard).
A 2x6 is 1 board foot per linear foot, a 2x12 is 2, and a 1x12 is 1. That makes quick checks easy.

How to calculate board feet

A board foot is a measure of volume: 144 cubic inches of wood, the same as a board 1 in. thick, 12 in. wide and 1 ft long. Minnesota's weights and measures law puts it plainly: in a sale of wood, a board foot means 144 cubic inches in any combination of length, thickness and width.

Board feet = thickness (in.) × width (in.) × length (ft) ÷ 12

Multiply by the number of pieces for the whole stack. The ÷ 12 is there because the length is in feet and the other two are in inches: 1 × 12 × 1 ÷ 12 = 1.

The same formula works with every measurement in inches if you divide by 144 instead: a 2 × 6 × 144 in. board is 2 × 6 × 144 ÷ 144 = 12 board feet, the same as 2 × 6 × 12 ÷ 12.

Nominal size	Board feet per linear ft	8 ft piece	12 ft piece	16 ft piece
1x4	0.33	2.67	4	5.33
1x6	0.5	4	6	8
1x12	1	8	12	16
2x4	0.67	5.33	8	10.67
2x6	1	8	12	16
2x8	1.33	10.67	16	21.33
2x10	1.67	13.33	20	26.67
2x12	2	16	24	32
4x4	1.33	10.67	16	21.33
6x6	3	24	36	48

Nominal size or actual size

Softwood lumber is named by its nominal size, and the nominal size is bigger than the board you get. The American Softwood Lumber Standard (PS 20, published by NIST) defines it that way: a dry 2 by 4 is surfaced to 1 1/2 by 3 1/2 in. It also says board measure is figured on the nominal thickness and width. So a 2x4 is tallied as 2 × 4 even though you could never measure 2 in. on it.

These are the minimum dressed dry sizes from PS 20, Table 3:

Nominal	Dressed, dry	Nominal	Dressed, dry
1 in.	3/4 in.	5 in.	4 1/2 in.
1 1/4 in.	1 in.	6 in.	5 1/2 in.
2 in.	1 1/2 in.	8 in.	7 1/4 in.
3 in.	2 1/2 in.	10 in.	9 1/4 in.
4 in.	3 1/2 in.	12 in.	11 1/4 in.

The calculator shows the dressed size next to every standard size you enter, so you can plan the real dimensions while you count on the nominal ones.

Two exceptions to know. Lumber made to a nonstandard size is tallied on the rough or nominal size it was made from (PS 20, 4.2). And lumber sold by cubic measure, rather than board measure, is figured on the dressed size (PS 20, 4.1). For hardwood and for rough-sawn stock, measure the boards you are buying and enter those numbers.

Worked examples

Deck joists. 30 pieces of 2x8, 12 ft long: 30 × 2 × 8 × 12 ÷ 12 = 480 board feet, 360 linear ft.

A mixed framing order. 10 pieces of 2x6 × 12 ft (120 board feet) and 5 pieces of 1x8 × 8 ft (5 × 1 × 8 × 8 ÷ 12 = 26.67) is 146.67 board feet. At your yard's price per board foot, P, the order is 146.67 × P. The calculator does that multiplication and carries each size into the estimate at its price per piece: a 2x6 × 12 ft is 12 board feet, so it costs 12 × P.

A hardwood slab. One rough board 2 in. thick, 10 in. wide and 8 ft long: 2 × 10 × 8 ÷ 12 = 13.33 board feet. Measure rough stock at its thickest and widest usable point, since that is what you are paying for.

Posts. 6 pieces of 6x6 × 10 ft: 6 × 6 × 6 × 10 ÷ 12 = 180 board feet.

Stair treads. 14 treads cut from 5/4 stock (1 1/4 in. nominal, dressed to 1 in. dry per PS 20), 12 in. wide and 4 ft long: 14 × 1.25 × 12 × 4 ÷ 12 = 70 board feet.

Mistakes to avoid. Mixing units is the usual one: the formula wants inches for thickness and width and feet for length. Entering the length in inches with ÷ 12 gives an answer 12 times too big. The second is using the dressed size for standard softwood, which undercounts against the yard's tally. The third is forgetting the pieces: the per-piece board feet times the count is the order.

Price per board foot, per piece or per linear foot

Lumber is priced three ways, and it pays to convert between them before you compare yards:

Per board foot. Multiply by the board feet.
Per piece. Price per board foot = price per piece ÷ board feet in the piece. A 2x6 × 12 ft at a given piece price works out to that price ÷ 12 per board foot.
Per linear foot. Price per board foot = price per linear foot ÷ board feet per linear foot (the second column of the first table).

For example, a 2x10 is 1.67 board feet per linear foot. If one yard quotes a 2x10 × 16 ft by the piece and another quotes 2x10 by the board foot, divide the piece price by 26.67 to compare them.

Add an allowance for defects and cut-offs if your jobs run one. Then press "Save as an estimate in Koira" to carry each size as a line, with its price per piece when you entered a price per board foot.

Reading a lumber tally and invoice

When a load of lumber arrives, the yard's tally lists what is on the truck. PS 20 says what an invoice for standard dressed lumber should show: the number of pieces of each nominal size and length, plus the actual thickness and width. That is enough to check the board feet yourself with this calculator before you pay.

A few tally rules from PS 20 are worth knowing:

Board rule tally. When boards of random widths are measured with a board rule, a piece that comes to an even half foot is counted alternately up and down. Fractions under the half are dropped and fractions over it go up to the next foot.
Average length. The total length in feet divided by the number of pieces.
Average width. For 1 in. stock, the total board feet divided by the total length, times 12. For thicker stock, divide the board feet by the nominal thickness first.

Board feet also convert straight to cubic feet: a cubic foot is 1,728 cubic inches, and a board foot is 144, so 12 board feet make one cubic foot. A 480 board foot order is 40 cubic feet on a nominal basis. That helps when you are checking whether a load fits a trailer or a rack. For weight, ask your supplier for the species and moisture they ship, since both change it a lot.

When contractors use board feet

Ordering hardwood for cabinets, stairs, built-ins and trim when your yard sells it by the board foot.
Comparing quotes from yards that price the same lumber differently.
Timber and post-and-beam work, to check the volume of a timber order.
Material totals for a framing package, as one number to check a supplier's quote against.

Board feet tell you volume, not how many pieces to cut a job from. For stud and plate counts, use the framing calculator; for sheet goods, the plywood and sheathing calculator. To turn material into a price with your margin, use the markup calculator.

Last checked October 8, 2026. More for your trade: how remodelers run on Koira.

FAQ

How do you calculate board feet?

Thickness in inches × width in inches × length in feet ÷ 12, times the number of pieces. A 2x6 × 12 ft is 2 × 6 × 12 ÷ 12 = 12 board feet.

How many board feet are in a 2x4x8?

2 × 4 × 8 ÷ 12 = 5.33 board feet, figured on the nominal size.

Do you use actual or nominal size for board feet?

Nominal for standard softwood lumber. The American Softwood Lumber Standard figures board measure on the nominal thickness and width, so a 2x4 counts as 2 × 4 even though it is dressed to 1 1/2 × 3 1/2 in. For rough or nonstandard stock, use the size it was made to or measure it.

How many cubic inches are in a board foot?

144. A board foot is 1 in. × 12 in. × 12 in., or any shape with the same volume.

How do I convert linear feet to board feet?

Multiply linear feet by thickness × width ÷ 12. For a 2x8, that is 2 × 8 ÷ 12 = 1.33 board feet per linear foot.

How do I compare a price per piece to a price per board foot?

Divide the piece price by the board feet in the piece. A 2x10 × 16 ft is 26.67 board feet, so its piece price ÷ 26.67 is its price per board foot.

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