Log Scaling Rules: Doyle vs Scribner vs International

Before a tree becomes boards, it is measured as a log. In the USA, there are three primary "rules" used to estimate how many board feet of lumber can be recovered from a log. Depending on which rule you use, the "yield" can vary by as much as 25% for the same log.

Why Multiple Rules Exist

Scaling rules were developed in the 19th and early 20th centuries before modern thin-kerf saws existed. They were designed to protect the sawmill owner by conservative estimation. Today, these rules are still the legal language of the North American timber trade.

The "Big Three" Comparison

Deep Dive: The Doyle Rule

Doyle is the oldest and most widely used rule in the Midwest and South. It uses a very simple formula: ((D-4)/4)^2 × L. However, because it subtracts a flat 4 inches for "kerf and shrinkage," it heavily penalizes logs smaller than 20 inches in diameter. If you are selling small hardwood logs, avoid Doyle if possible.

Deep Dive: The International 1/4" Rule

This is the standard for modern forestry science. It accounts for a 1/4 inch saw kerf and logarithmic taper. If you have a highly efficient sawmill (like a Wood-Mizer bandsaw), your actual board foot yield (overrun) will closely match the International result.

How to Measure a Log

To get an accurate scale, you must measure the Small End Diameter (SED) inside the bark. Measuring the large end will give you a false high yield that the log cannot physically produce.

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