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Board Feet Calc

Board Foot Calculator

A free board feet calculator: tally mixed lumber into board feet and cost, or turn a finished cut list into the rough boards to buy.

ExampleA walnut, white oak and poplar order. Edit it or clear it to start your own.

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10 pcs · total50.67 BF · $345.95

How it's measured

One board foot is 12″ × 12″ × 1″, or 144 cubic inches (NIST Handbook 130). So board feet = thickness × width × length, all in inches, ÷ 144. With the length in feet, divide by 12 instead.

BF = T × W × L ÷ 144

Quarters. Hardwood thickness is sold in quarters of an inch: 4/4 is 1″, 5/4 is 1-1/4″, 8/4 is 2″. The calculator uses the nominal quarter thickness, because hardwood is measured before it's surfaced (NHLA rules).

Thin stock. Anything under 1″ thick counts as 1″ in hardwood board measure, so a custom 3/4″ thickness is tallied as 1″.

Rough vs surfaced

Rough lumber comes straight from the sawmill; surfaced (S2S) lumber has been planed on both faces. Planing takes off 3/16″ up to 6/4 and 1/4″ from 7/4 to 16/4, so 4/4 surfaces to 13/16″ and 8/4 to 1-3/4″ (NHLA, USDA Wood Handbook). You still pay for the rough thickness.

Finished → rough works backwards from your plan: each finished part gets the smallest quarter that surfaces to its thickness, plus 1/4″ of width and 1″ of length (USDA Forest Service rough-mill allowances), then the list is grouped by species and quarter with about 20% waste (trade guidance, not a rule). The buy quantity rounds up to whole board feet so you don't come home short.

Metric lists use 1″ = 25.4 mm exactly (NIST Handbook 44): 1 board foot = 0.002359737 m³.

How to calculate board feet, with worked examples

Sources

  1. National Institute of Standards and Technology. Handbook 130, Uniform Laws and Regulations: IV-B Method of Sale of Commodities. 2026. Used: §2.12.1.1 Board Foot: the volume of a board 1 ft long, 1 ft wide and 1 in. thick, or its equivalent (144 in³ of wood).
  2. National Hardwood Lumber Association. Rules for the Measurement & Inspection of Hardwood & Cypress. Effective January 1, 2023. Used: ¶14 standard thicknesses for surfaced (S2S) lumber; ¶16 board measure: standard thicknesses under 1 in. (thin stock) count as 1 in., measured before surfacing.
  3. USDA Forest Service, Forest Products Laboratory. Wood Handbook: Wood as an Engineering Material, Chapter 6, Commercial Lumber, Round Timbers, and Ties. General Technical Report FPL-GTR-190, 2010. David E. Kretschmann. Used: Table 6-4, standard thickness values for rough and surfaced (S2S) hardwood lumber; footnote a: above 4 in. rough the finished size is not specified (special contract).
  4. USDA Forest Service, Northeastern Research Station. Rough Mill Improvement Guide for Managers and Supervisors (GTR-NE-329). June 2005. Philip H. Mitchell, Jan Wiedenbeck, Bobby Ammerman. Used: Trim Allowance: the standard 1 in. over the final finished part length; edge allowance: the traditional 1/4 in. of extra width (a 1-3/4 in. rough part machined to 1-1/2 in.).
  5. Popular Woodworking. Buying Hardwood Lumber – Two Approaches. June 3, 2008. Robert W. Lang. Used: Trade guidance: about 20% extra (a bookcase of a little less than 40 BF, bought 49); about 50% extra when the mill picks the boards (random widths and lengths): a workbench of about 80 BF. Trade guidance, not a rule.
  6. National Institute of Standards and Technology. Handbook 44, Appendix C: General Tables of Units of Measurement. 2026. Used: 1 inch = 2.54 centimeters (exactly).