Scribner Decimal C – the log rule of the western US

A rule built by drawing boards into circles, today the standard for softwood logs in the western United States.

What is the Scribner Decimal C?

The Scribner log rule gives log volume in board feet from the small-end diameter and the length. It was created by drawing 1-inch boards with a ¼-inch kerf into circles of different diameters. The Decimal C version rounds the result to tens of board feet and drops the last zero.

Formula

BF ≈ (0.79 · D² − 2 · D − 4) · L / 16

The original rule is a table; the formula is only an approximation. D = small-end diameter in inches, L = length in feet. Decimal C rounds to 10 BF – a value of “16” means 160 BF.

Worked example

A log 16 inches at the small end and 16 feet long scales 160 BF by the Scribner Decimal C table (written as 16).

Where it is used

The western United States and Canada, mainly softwood logs. The USDA Forest Service uses it for timber sales in the West.

Doyle vs Scribner vs International ¼″ ›

Frequently asked questions

Why does Scribner have no exact formula?

The rule was made by drawing boards into circles, not by calculation. The official rule is therefore a table; formulas exist only as approximations.

What does “Decimal C” mean?

Table values are rounded to tens of board feet and the last zero is dropped. So 16 means 160 BF.

How does Scribner differ from International ¼″?

Scribner ignores log taper, so it gives less on long logs. A 16″ × 16 ft log scales 160 BF by Scribner and 180 BF by International ¼″.

Other log scaling methods

All 22 methods in the app ›

In your countryHoppus formulaA traditional British rule still used in the tropical hardwood and teak trade.m³ · GB · IE · IN · GH · MY Huber formulaThe most widely used scaling method in Central Europe: one diameter at mid-length and the length.m³ · SK · CZ · DE · AT · FR · IE Smalian formulaWhen you cannot reach the middle of the log – on a deck or a truck – you measure both ends.m³ · US · CA Doyle Log RuleThe oldest log rule still in wide use in the southern and midwestern United States.BF · US International ¼″ Log RuleIt allows for a ¼-inch kerf, shrinkage and log taper, so it comes closest to the real sawn timber yield.BF · US JAS (Japanese standard)The small-end diameter squared method, the standard for logs traded to Japan.m³ · JP Swedish scaling (toppmätning)Swedish sawmills pay by the small-end diameter: m³to is a cylinder from the top end.m³ · SE STN / ČSN 48 0009Table-based scaling under the Slovak standard STN 48 0009 and the Czech ČSN 48 0009: under-bark volume from tables by mid diameter, length and species. Commonly used in the roundwood trade in Slovakia and Czechia.m³ · SK · CZ More methodsMid-girth, Newton, GOST 2708-75, Brereton, Vermont, Universal (Daniels), Ontario Board Foot, Ontario Cubic, Roy, Alberta, BC Firmwood, Guo Biao (GB/T 4814)All 22 methods ›