Scribner Log RuleDiagram-Based Volume Calculator
Principal log scaling rule for western USA softwoods. More accurate than Doyle for large-diameter logs. Scribner Decimal C is the official USFS standard for national forest timber sales.
Why this calculation matters
Scribner ignores taper, so long logs are under-scaled. It remains the legal rule for much public timber, whatever its accuracy.
Scribner Log Rule
Diagram-Based Volume Calculator
This picker does not change the answer. Board feet depends only on the dimensions you enter, not on the species — that is what makes it a rule rather than an estimate. The species is here so you can note it on a printout.
Measured over bark. If your figure is already inside bark (DIB), set bark to 0.
| Log Rule | BF per Log | Total BF | vs Scribner |
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About Scribner Log Rule
Developed by J.M. Scribner in 1846 using diagram-based cross-section drawings. The Scribner Decimal C variant is the official US Forest Service standard, rounding volumes to the nearest 10 BF. More accurate than Doyle for large logs and preferred for Pacific Northwest softwoods including Douglas Fir and Redwood. It also works as a complete Scribner Decimal C reference, so you can retire the printed log scale tables and get exact figures for any diameter.
Where Used?
Formulas
Scribner = (0.79 x D^2 - 2 x D - 4) x (L / 16) BF, D=in DIB, L=ftDecimal C = floor(BF / 10) x 10 official USFS rounded form- Scribner log rule (published rule)
Formula checked against the sources above by an automated regression test (tests/test-calculators.js) that derives each expected value independently of this page. Last reviewed .
FAQ
Wood species data
Density, hardness and movement for 60 timbers
How the calculation works
The formula is a continuous approximation of the diagrams Scribner drew in 1846 by fitting one-inch boards inside a circle and counting them. Decimal C is the same number rounded to the nearest ten board feet and written with the final zero dropped, so 96 board feet is scaled as 100 and shown as “10”.
Show the formula
Board feet = (0.79 x D^2 - 2D - 4) x L / 16, with D the small-end diameter inside bark in inches and L the length in feet. Decimal C = that figure rounded to the nearest 10 board feet, where a remainder of 5 rounds down and 6 rounds up.Taper is ignored by design, so the rule under-reads logs longer than 16 ft. Decimal C rounding follows the USFS scaling convention (5 down, 6 up).
References and what each one provides
- USDA Wood Handbook (FPL GTR-190)USDA Forest Products LaboratoryPublished density, moisture relationships, shrinkage coefficients and mechanical properties for a wide range of species. The reference dataset behind most wood-property figures on this site.
Unverified values are marked as such rather than presented as sourced.
Limitations of this calculation
Applies the Scribner diagram rule as published. It ignores taper entirely by design, and does not account for actual recovery, sawing pattern, or log defect.
Do not use this for Sale settlement unless Scribner is the agreed rule. It ignores taper by design.
Figures are engineering estimates from the inputs and assumptions shown. Verify against the actual material and, where the result affects structure or safety, against a qualified professional.
How to use this tool
- Enter the log measurements below, then press Calculate.
- Pick your scale type from the dropdown.
- Fill in small-end diameter, log length, number of logs, bark each side.
- Press Calculate.
Worked example
Common mistakes to avoid
- Reading the decimal-C table as board feet. Decimal C is in tens of board feet.
- Using Scribner on very long logs without segmenting. Scale long logs in two lengths.
- Expecting Scribner and Doyle to agree. On small logs they differ a lot — state which rule the deal uses.