Formulas and sources
Each formula this calculator uses, where it comes from, and what it leaves out. "How it works" shows the same formula with your own numbers.
Board feet, exact
- Board feet
- the volume, 144 cubic inches each
- T
- the thickness billed, in inches (4/4 is 1, a 2× is 2)
- W
- the width, in inches
- L
- the length, in inches
For one board: a row of several is that times its pieces, and a row given as its total length counts that length once. With the length in feet, divide by 12 instead of 144. Softwood is counted on its nominal size and hardwood on its rough thickness, before planing. A tapered board is counted at its average width. Nothing is rounded.
Source: The board foot, 12" × 12" × 1" = 144 in³, and the count on the size before surfacing, from [1]; board measure on nominal sizes from [2].
Board feet, as a hardwood tally
- Face
- one board’s surface measure, in square feet
- Tally
- the board feet the tally counts
Hardwood, board by board: the length dropped to the whole foot, the face rounded to the nearest square foot, then multiplied by the thickness, a board under 1" counted as 1". A tapered board is measured a third of its length from the narrow end. A face of exactly a half rounds down, or up and down in turn. Softwood rows, and rows given as a total length, stay by board measure, as exactly. A rough thickness typed by hand is tallied as typed, where the rules count the quarter it grades as.
Source: The tally, the rounding in turn and the tapered board from [1] (¶16–17); an exact half rounded down, the retail rule, from [3] (§2.12).
The finished size
For sizes the tables list
Hardwood surfaced two sides keeps its width and loses 3/16" of thickness (1/4" from 1 3/4"): 4/4 is 13/16". Softwood is dressed on both: a 2 × 4 is 1 1/2" × 3 1/2" dry. A thickness typed by hand, or a softwood width the table does not list, has no finished size, and the figure is left out.
Source: Hardwood S2S thicknesses from [1] (¶14) and [4] (Table 6-4); softwood dressed sizes from [2] (Table 3).
Waste
With waste
- Waste
- the waste percentage
Board feet in the count chosen, exact or tallied. Waste is added once, as a share of the board feet: 15% turns 100 into 115. The card shows the exact figure under the whole one: 66 2/3 with 15% is 76 2/3, so 77 to buy.
Source: Standard formula; no single publisher.
Cost
With a price
Row by row, on the board feet in the count chosen. A price per thousand board feet is divided by 1,000, a price per linear foot is times the row’s linear feet, and a price each is times its pieces (a total length takes none). With waste, the cost is times (1 + Waste ÷ 100) as well: on the exact allowance, not the whole board feet to buy.
Source: Standard formula; no single publisher.
Length and volume
Board feet in the count chosen. Cubic meters are the same volume, 144 cubic inches a board foot at 2.54 cm an inch, not a count of metric lumber.
Source: Uses 1,728 in³ = 1 ft³ and the inch of 2.54 cm from [5]; [2] (Appendix B1) warns that board feet and cubic meters of lumber do not convert as one.
Sources
- National Hardwood Lumber Association. Rules for the Measurement & Inspection of Hardwood & Cypress, ¶13–14 (standard thicknesses, and surfaced two sides), ¶16 (measurement and tally), ¶17 (tapering lumber). Effective January 1, 2023.Our automated tests check this calculator against 21 cases from it.
- National Institute of Standards and Technology. PS 20-25, American Softwood Lumber Standard, §2.2 (board measure), §4.3 (tally), Table 3 (minimum dressed sizes), Appendix B1. January 2025.Our automated tests check this calculator against 9 cases from it.
- National Institute of Standards and Technology. NIST Handbook 130, Uniform Regulation for the Method of Sale of Commodities, §2.10 (softwood lumber) and §2.12 (hardwood lumber, retail sales). 2026 edition.Our automated tests check this calculator against 2 cases from it.
- USDA Forest Service, Forest Products Laboratory. Wood Handbook: Wood as an Engineering Material (FPL-GTR-282), Chapter 6, Table 6-4, standard hardwood thicknesses, rough and surfaced two sides. 2021.Our automated tests check this calculator against 13 cases from it.
- National Institute of Standards and Technology. NIST Handbook 44, Appendix C: General Tables of Units of Measurement, the international foot, 12 × 0.0254 m = 0.3048 m exactly, and p. C-6 (1,728 in³ = 1 ft³). 2026 edition.Our automated tests check this calculator against 2 cases from it.
What this calculator does not cover
- Logs: Doyle, Scribner and International 1/4" estimate the lumber a log will yield, a different measure.
- Firewood: it is sold by the cord, never by the board foot.
- A yard’s own habits, such as rounding widths to the inch: ask your seller how they count.
- Weight: it depends on the species and how dry the wood is.
Sources checked on .