Board feet calculator for lumber

A board foot is 144 cubic inches of lumber — a piece one inch thick, twelve inches wide and twelve inches long. The formula is thickness in inches x width in inches x length in feet, divided by 12, and it is the unit hardwood is sold in because it measures the material rather than the length.

Thickness (in)

Nominal thickness: a 2x4 is 1.5 in actual but 2 in nominal.

Width (in)

Length (ft)

Quantity (boards)

Board feet

53.33bd ft

Linear feet 80.0 lin ftVolume 4.44 ft³

Nominal dimensions only, with no allowance for milling loss or defects. A mill's tally on the invoice is the figure that matters for payment.

Dimension lumber from a home centre is priced per piece or per linear foot, so board feet only matters when you buy hardwood, rough-sawn stock or lumber from a mill. That is also where the nominal-versus-actual trap bites: a 2x4 is 1.5 x 3.5 inches dressed, but it is still sold and calculated as 2 x 4 for board-foot purposes. Use the nominal figure for pricing and the actual figure for fit.

The third number worth knowing is yield. Rough lumber is sold in random widths and lengths, and a 100 board-foot bundle will not produce 100 board feet of finished parts — planing, jointing and trimming remove 20 to 30 percent, and defects remove more. Order by the finished requirement plus that margin, not by the finish figure alone.

How the calculation works

Board feet per piece = (thickness in x width in x length ft) / 12. Total board feet = that figure x quantity. Linear feet = length x quantity. Cubic feet = board feet / 12.

• Dimensions are nominal for pricing purposes, which is how mills and suppliers quote board feet.
• Length is in feet and thickness and width are in inches, as the formula requires.
• No allowance is made for planing, jointing, trim or defects; add 20-30 percent for finished parts from rough stock.
• Board feet measure volume, not quality — a board foot of clear stock and one of knotty stock are the same unit and very different prices.

Sources: Board foot definition: 144 cubic inches (1 in x 12 in x 12 in); Softwood nominal vs dressed sizes per US lumber standards (e.g. 2x4 = 1.5 x 3.5 in)

Worked examples

Questions

What is a board foot?

144 cubic inches of lumber: 1 inch thick, 12 inches wide, 12 inches long. It is the standard unit for hardwood and rough-sawn lumber.

How many board feet in a 2 x 4 x 8?

5.33. The formula is 2 x 4 x 8 / 12. A 2 x 4 x 10 is 6.67 board feet and a 2 x 6 x 8 is 8.

How many board feet in a 1 x 12 x 8?

8 board feet: 1 x 12 x 8 / 12 = 8. That is the same volume as a 2 x 6 x 8, which is why board footage compares unlike shapes.

Do I use nominal or actual thickness?

Nominal for pricing, since that is what the supplier quotes; actual for fitting. A dressed 2x4 is 1.5 x 3.5 in but is still sold as 2x4.

How much extra should I buy for milling?

20-30 percent over the finished requirement if you are planing rough stock, and more if the boards have defects you need to cut around.

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Written and maintained by Sam Winters. Last updated 2026-11-04. Every figure is computed in your browser; nothing you enter is sent anywhere. Found an error? Tell me — accuracy reports get fixed first.