Do you use nominal or actual lumber dimensions?

Use nominal. A 2x4 is calculated as 2" × 4" even though the actual milled size is 1.5" × 3.5". Lumberyards bill by nominal — that's the industry standard.

How many board feet in a 2x4 by 8 ft long?

5.33 board feet. Calculation: (2 × 4 × 8) / 12 = 5.33 bd ft. A bundle of 100 such 2x4s contains 533 board feet.

Is board foot the same as linear foot?

No. A linear foot is a length only. A board foot is a volume — length × width × thickness. Most dimensional framing lumber is priced per piece or per linear foot; rough sawn and hardwood lumber is priced per board foot.

Board Foot Calculator

Board feet from lumber thickness, width, and length — straight or in stack of pieces. Use nominal dimensions, just like the lumberyard does.

Thickness (in, nominal)

Width (in, nominal)

Length

Pieces

Waste factor

Price per board foot (optional)

spacer

Total board feet

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— per piece

Total linear feet

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Volume

—

ft³

Estimated cost

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enter $/bd ft

What a board foot is

A board foot is the standard volume unit for lumber: a piece 1 inch thick, 12 inches wide, and 12 inches long. That's 144 cubic inches. Anything that adds up to 144 cubic inches is 1 board foot, regardless of shape — a 2"×6"×12" piece, a 1"×6"×24" piece, and a 1"×12"×12" piece are all exactly 1 bd ft.

Board feet = (T × W × L) / 144 (all in inches) Board feet = (T × W × L) / 12 (T,W in inches, L in feet)

Nominal vs actual — use nominal

Dimensional lumber is sold by nominal size. A 2x4 is calculated as 2" × 4" for board-foot pricing even though the actual milled cross-section is 1-1/2" × 3-1/2". Every lumberyard bills this way. If you calculate by actual dimensions you'll get a smaller number and you'll pay for more wood than you measured.

Worked example: a deck frame

Say you need 14 pieces of 2×8 × 12 ft for joists. Per piece: (2 × 8 × 12) / 12 = 16 bd ft. Total: 14 × 16 = 224 bd ft. At $3.50/bd ft, that's $784 in joists before tax. Add 10% for waste and end-cuts and call it $865.

When board foot vs linear foot matters

Linear foot pricing: common for SPF studs, treated PT, plywood (per sheet). The lumberyard already does the math for you.
Board foot pricing: hardwoods (oak, maple, walnut), rough-sawn lumber, custom widths, sawmill-direct purchases. You hand the yard your bd ft count and they cut the price from there.

Nominal vs actual lumber dimensions

Use nominal in this calculator — these are the actual milled dimensions for reference only.

Nominal	Actual	bd ft / linear ft
1×2	3/4" × 1-1/2"	0.17
1×3	3/4" × 2-1/2"	0.25
1×4	3/4" × 3-1/2"	0.33
1×6	3/4" × 5-1/2"	0.50
1×8	3/4" × 7-1/4"	0.67
1×10	3/4" × 9-1/4"	0.83
1×12	3/4" × 11-1/4"	1.00
2×2	1-1/2" × 1-1/2"	0.33
2×3	1-1/2" × 2-1/2"	0.50
2×4	1-1/2" × 3-1/2"	0.67
2×6	1-1/2" × 5-1/2"	1.00
2×8	1-1/2" × 7-1/4"	1.33
2×10	1-1/2" × 9-1/4"	1.67
2×12	1-1/2" × 11-1/4"	2.00
4×4	3-1/2" × 3-1/2"	1.33
4×6	3-1/2" × 5-1/2"	2.00
6×6	5-1/2" × 5-1/2"	3.00

Frequently asked questions

What is a board foot?

A volume of lumber equal to 144 cubic inches — a 1" thick by 12" × 12" piece, or anything that adds up to the same volume.

What is the board foot formula?

(T × W × L) / 144 with all dimensions in inches, or (T × W × L) / 12 if length is in feet. Use nominal dimensions.

Nominal or actual?

Always nominal. The lumberyard bills you for the nominal volume. A 2×4 is calculated as 2 × 4, not 1.5 × 3.5.

How many bd ft in a 2x4 × 8 ft?

5.33 bd ft. (2 × 4 × 8) / 12 = 5.33.

Board foot vs linear foot?

Linear foot is length only. Board foot is volume. Hardwoods and rough-sawn lumber are sold by board foot. Most framing lumber is sold per piece or per linear foot.