Board foot calculator

How to calculate board feet

A board foot is a volume of wood: a piece 1 inch thick, 12 inches wide and 12 inches long, or 144 cubic inches[3][4]. Multiply thickness by width by length and divide by 144 when all three are in inches. With the length in feet, divide by 12 instead.

board feet = thickness (in) × width (in) × length (ft) ÷ 12

For example, a board 1 inch thick, 6 inches wide and 8 feet long is 1 × 6 × 8 ÷ 12 = 4 board feet. Ten of them are 40 board feet. In metric, work out the volume and divide by 0.002360 m³ per board foot[10]. One cubic foot is 12 board feet.

Nominal and actual sizes (softwood)

Construction lumber such as pine, fir and spruce is named by its nominal size. A 2×4 is really about 1-1/2 × 3-1/2 inches once it is dried and planed [1][2]. The softwood lumber standard counts board feet from the nominal size, not the planed size [1]. So a 2×4 that is 8 feet long is sold as 5.33 board feet, although it contains about 3.5 board feet of wood. Choose “Softwood, nominal sizes” and the calculator shows both.

Quarter sizes: 4/4, 5/4, 8/4 (hardwood)

Hardwood is sawn and sold by its rough thickness in quarters of an inch: 4/4 is 1 inch, 5/4 is 1-1/4 inches and 8/4 is 2 inches [3]. Planing both faces (S2S) takes off 3/16 inch up to 6/4 and 1/4 inch from 7/4 up[2][3]. Enter the quarter size as the thickness; the calculator accepts “4/4” as typed. Ask your supplier whether a price per board foot is based on the rough or the planed thickness.

Lumber yards tally hardwood board by board. Under the hardwood grading rules, random widths are rounded to the nearest inch and lengths down to the whole foot before board feet are counted [3], so an invoice can differ slightly from the exact figure here.

Price and waste

Enter the price your yard quotes and pick how it is quoted: per board foot, per thousand board feet (MBF), per linear foot or meter, or per cubic meter. The waste percentage adds extra board feet (and cost) on top of the cut list for offcuts, defects and mistakes. How much to allow depends on the grade of lumber and the project, so it starts blank.

Log scale: Doyle, Scribner and International 1/4″

A log rule estimates how many board feet of lumber a sawmill can cut from a log, from the diameter inside the bark at the small end and the log length [4][5]. The three rules in common use give very different answers for the same log, so buyers and sellers should agree on the rule first [4][5].

• Doyle: (D − 4)² × L ÷ 16 [4][5]. The most widely used rule, especially on private timber in the East and South. It takes too much off small logs and too little off large ones, so it scales small logs low.
• Scribner Decimal C: J.M. Scribner drew 1-inch boards inside circles in 1846; Decimal C rounds those volumes to the nearest 10 board feet and drops the last zero [5][9]. Tables list 16 for 160 board feet [7]. It is the most used rule in the Pacific Northwest and common on the West Coast and for southern pine [4][9]. The calculator reads it from the published table [5][6].
• International 1/4-inch: Judson Clark’s rule allows for a 1/4-inch saw kerf and assumes the log widens 1/2 inch every 4 feet. Each 4-foot section scales 0.199D² − 0.642D board feet, at a diameter 1/2 inch larger than the section before, and the total is rounded to the nearest 5 board feet [4][5]. Of the three it comes closest to the lumber actually sawn[4][5].

Measuring a log

• Measure the small end inside the bark. If it isn’t round, take two measurements at right angles and average them[5][7].
• Diameters are tallied to the nearest inch: 12-1/4 counts as 12 and 12-3/4 as 13 [4][7]. At exactly a half inch the calculator rounds down, as Idaho does for an averaged diameter [7].
• Length is scaled in whole feet. The few extra inches left for trimming the ends are ignored, so a log measuring 16 ft 6 in scales as 16 ft [5][7].
• The rules here run from 6 to 40 inches and 6 to 20 feet. Scale a log longer than 20 feet as two or more logs[5][9].

Where published tables disagree

• International: for six sizes (for example 15 in × 16 ft) the published tables are 5 board feet higher than the formula. The calculator uses the table value [5][8].
• Doyle: when the formula lands on exactly half a board foot, some tables round down and others up[5][8]. The calculator rounds up.
• Scribner: for the smallest logs (6 in up to 9 ft, 7 in at 6 ft), eastern tables list 5 board feet[5][8] and the Idaho table lists 10 [6]. The calculator shows 5 and notes the difference. Values for 19-foot logs and 39-inch diameters appear only in the Idaho table, so they are marked as such.

Limits

These are gross scales of sound, straight logs. Professional scalers deduct for rot, splits, sweep and crook, which this calculator doesn’t do [4][5]. Mills often saw more lumber than the scale says (overrun), especially under the Doyle rule on small logs [5][9]. To estimate standing trees, foresters use tree volume tables based on diameter at breast height instead [5].

Common questions

How many board feet are in a 2×4×8?

5.33 board feet, because board feet for softwood lumber use the nominal 2 × 4 inch size [1]: 2 × 4 × 8 ÷ 12. The actual 1-1/2 × 3-1/2 inch board holds 3.5 board feet of wood.

What does 4/4 mean in lumber?

Four quarters of an inch, or 1 inch of rough-sawn thickness [3]. After planing both faces it is usually 13/16 inch [2][3]. 8/4 is 2 inches rough and about 1-3/4 inches planed.

How do I convert linear feet to board feet?

Multiply the linear feet by the thickness and width in inches and divide by 12. A 1×6 has 0.5 board feet per linear foot, so 20 linear feet is 10 board feet.

How do I convert board feet to cubic feet or cubic meters?

Divide board feet by 12 for cubic feet. Multiply by 0.002360 for cubic meters, so 1,000 board feet is about 2.36 m³.

How many board feet are in a log?

It depends on the log rule. A log 16 inches across the small end and 16 feet long scales 144 board feet by Doyle, 160 by Scribner Decimal C and 180 by the International 1/4-inch rule [5][6][8]. Use the Log scale tab above for your logs.

Which log rule should I use?

Use the rule your buyer or sawmill uses; it is usually set by local custom [4][5]. If you want the closest estimate of the lumber you’ll get, the International 1/4-inch rule is the most accurate of the three[4][5].

Sources

1. NIST, Voluntary Product Standard PS 20-20, “American Softwood Lumber Standard” (2020)Board measure from nominal thickness × nominal width × length (§2.2); nominal and minimum dressed sizes (Table 3)
2. USDA Forest Products Laboratory, Wood Handbook (FPL-GTR-282, 2021), Chapter 6 “Commercial Lumber, Round Timbers, and Ties”Softwood nominal and dressed sizes (Table 6-6); hardwood rough and surfaced thicknesses (Table 6-4)
3. American Hardwood Export Council, “Grading sawn lumber: Measurement”Board foot = width (in) × length (ft) × thickness (in) ÷ 12; quarter thicknesses 4/4–16/4; surfaced thickness rule; tally rounding
4. Bond, B., “Understanding Log Scales and Log Rules” (University of Tennessee Extension PB1650)Board foot = 144 in³; Doyle formula; International 1/4-inch formulas; 16-ft comparison table; diameters to the nearest inch
5. Cassens, D., “Log and Tree Scaling Techniques” (Purdue Extension FNR-191)Doyle, Scribner and International rules: formulas, method and Tables 1, 2 and 3; length to the whole foot; logs over 20 ft
6. Idaho Board of Scaling Practices, “Coconino Scribner Decimal C Volume Table”Scribner Decimal C table, 6–40 in by 6–20 ft
7. Idaho Department of Lands, Forestry Contest Manual, Chapter 1 “Log Scaling” (2025)Decimal C means tens of board feet; whole-inch diameter and whole-foot length rules; worked examples
8. Briggs, D., “Appendix 3. Board Foot Log Rules” (University of Washington, Rural Technology Initiative), excerpting Koch (1972)International 1/4-inch, Doyle and Scribner Decimal C tables, 6–30 in by 6–16 ft (used as test values)
9. Oregon State University Extension, “Measuring Timber Products Harvested from Your Woodland” (EC 1127)Scribner Decimal C rounds to the nearest 10 bd ft; eastern Oregon scales logs as one log up to 20 ft
10. NIST Special Publication 811, Appendix B.9: conversion factorsInch, pound, ounce, gallon and fluid-ounce conversions