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Board Foot Calculator

Thickness, width and length to board feet and lumber cost.

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Board footage

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Rough-sawn sizes aren't the size you think

A "1 in" board off a sawmill is often a true 1 in before drying and planing, but a dimensional 2x4 from the lumber yard measures a true 1.5 x 3.5 in. Use the actual measured thickness and width, not the nominal size, or your board footage will be off.

A board foot is a volume measurement: one board foot equals 144 cubic inches, the size of a board 1 in thick, 12 in wide, and 12 in long. The formula is thickness (in) × width (in) × length (in), divided by 144. This is the standard unit for pricing rough-sawn hardwood and specialty lumber, since it accounts for all three dimensions rather than just linear feet.

For a log's board footage rather than a milled board's, sawmills commonly use the Doyle rule: (diameter minus 4) squared, times length in feet, divided by 16. Doyle tends to underestimate yield on smaller logs and is most accurate on larger, higher-grade logs, which is part of why it remains popular with sellers.

Dimensional framing lumber (2x4, 2x6, etc.) is priced by the linear foot, not the board foot, so this calculator is most useful for hardwood, specialty softwood, and rough-sawn material sold by board foot.

Where these numbers come from

These are planning estimates. Check product labels, your local building code, and a licensed contractor before you buy materials or build.

Frequently asked questions

Do I use the nominal size or the actual measured size?

Always the actual measured dimensions. A finished 2x4 measures roughly 1.5 x 3.5 in, not 2 x 4 in, so using nominal sizes overstates your board footage by close to 30%.

How is a log's board footage different from a milled board's?

A log's usable board footage accounts for the round shape and saw kerf loss, so mills use a separate log rule (commonly Doyle) rather than the milled-board formula. It estimates finished lumber yield from a log's diameter and length, not its own volume.

Why is hardwood priced by the board foot instead of linear feet?

Hardwood boards vary in width and thickness, unlike dimensional softwood lumber which is milled to a few fixed sizes. Board footage lets a mill price any width or thickness consistently by volume rather than needing a different price list for every size.

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