Log scaling and log rules: what the Forest Service, Purdue Extension and New York DEC say about Doyle, Scribner and International

Prices in a timber or log report only mean something with the unit and the rule behind them. This page sets out what three official and university sources say about scaling and the log rules. It reports volume methods and does not give prices. For price series, see log and timber prices.

What scaling is

The US Forest Service log scaling page says scaling is the determination of the gross and net volume of logs, and that its main purpose is to fix the volume by product or species that will be charged at a set rate, called "scaling for payment". It describes conventional scaling as measuring log diameters and lengths and applying an approved set of rules to deduct for defects. Every log in every load can be scaled, which it calls 1-in-1 or 100%, or an approved sampling method can be used, such as scaling a portion of the loads, 3P scaling or sample weight scaling. It adds that weight scaling is used more often, especially on low value material where there is a single species or product, or where all products weighed are of close to the same value. Scale volume may be expressed in cubic feet, board feet, cords, tons, linear feet or number of pieces.

The three rules in common use

Purdue Extension publication FNR-191, "Log and Tree Scaling Techniques" by Daniel Cassens, says the United States and Canada have had over 95 log scaling rules bearing about 185 names, and that only Doyle, Scribner and International are widely recognized. The table sets out what it says about each.

Rule	Type and origin	What Purdue says
Doyle	Formula rule. Earliest surviving version published in 1837 in Rochester, New York; very likely dates to 1825.	Used more than any other rule, above all on private timber in the east and south. The formula takes four inches off the diameter for slabs and edgings, squares what is left and scales it by log length. It ignores taper, and it seriously under scales small logs and over scales large logs.
Scribner	Diagram rule. First published in 1846 by J. M. Scribner, from boards fitted into circles representing log ends, with a 1/4 inch kerf allowance.	Widely used by the Forest Service in the Lake States and the western United States, and since replaced there by cubic volume measurement. Scribner Decimal C, the most prevalent form, rounds volume to the nearest 10 board feet, so volumes change as a step function with diameter and length.
International	Formula rule. Developed by Judson F. Clark in 1900 while working for the Province of Ontario; the 1/4 inch kerf version came in 1917.	Probably the most accurate of the rules it covers but little used. It is one of the few rules with a basis for log taper, assuming a 1/2 inch change in diameter for every 4 feet of length.

Purdue says there is no simple answer on which rule is best, that local tradition usually decides which is used, and that the rules are fair as long as everyone uses the same one. It describes overrun as the number of board feet a mill produces beyond what the log scale indicated, and lists the log rule, scaling practice, roughness, taper, diameter, length, species, slab and edging practice, sawing variation and kerf among the factors that move it. If the aim is the closest estimate of lumber produced, it says the International scale would be preferred, with some adjustment for overrun or underrun.

Scaling by hand varies

The Purdue publication reports a contest in which 14 knowledgeable timbermen scaled 11 logs and gave 14 different answers, with an average of 1544 board feet Doyle and a range from 1434 to 1795. After each log was examined, the agreed volume was 1589 board feet. It names length measured by eye, diameter taken in one direction instead of two at right angles inside the bark, rounding of fractions of an inch, and bucking through swollen areas as sources of difference.

Which rule a region uses

The New York State Department of Environmental Conservation Winter 2025 stumpage price report says that in most cases each rule gives a different volume estimate for identical trees, and that each region of the state has a most commonly used rule. The report prices Western/Central New York in Doyle, the Adirondack and Hudson/Mohawk regions in International 1/4 inch, and Delaware/Catskill in Scribner.