---
title: "Doyle, Scribner and International Log Rules Compared"
description: "How the three classic board-foot log rules differ: the Doyle formula, Scribner Decimal C, International ¼-inch accuracy, their biases on small and large logs, and what overrun really measures."
image: "https://nestingcalc.com/og-default.png"
url: "https://nestingcalc.com/guides/log-rules-doyle-scribner-international/"
locale: "en"
---

# Doyle, Scribner and International Log Rules Compared

How the three classic board-foot log rules differ: the Doyle formula, Scribner Decimal C, International ¼-inch accuracy, their biases on small and large logs, and what overrun really measures.

## What a log rule is

A log rule predicts the board feet of lumber a log will yield from its diameter and length — before anyone cuts it. It is not a volume measurement: every rule builds in assumptions about taper, kerf and edging loss, and each rule embeds different ones, which is why the same log scales differently under Doyle, Scribner and International.

## Doyle — the trader's rule

The oldest rule (1820s): **bf = (d − 4)² × L ÷ 16** with d = small-end diameter inside bark in inches. The subtracted 4 inches is a slab allowance, which crushes the estimate on small logs — a 10 in, 16 ft log scales (10−4)² × 16 ÷ 16 = **36 bf**. Buyers of small hardwood logs love Doyle; sellers lose. Despite (because of) this, it remains the cash standard of the US South hardwood trade.

## Scribner — the diagram rule

J.M. Scribner (1840s) drew one-inch boards inside scaled log-end circles and summed them. Practical editions publish **Scribner Decimal C**, which rounds each log to the nearest 10 board feet. The rule is comparatively fair on mid-sized logs and conservative on large ones; it underpinned US West timber sales for a century and still appears in stumpage contracts.

## International ¼-inch — the accuracy yardstick

Built as a model, not a guess: it assumes a ¼-inch kerf plus shrinkage and taper. Per 4-foot section, **bf ≈ 0.199 d² − 0.642 d** (d in inches), adding ½ inch of taper per section; a 10 in section therefore yields ≈ 13.5 bf. USDA studies repeatedly found it tracks actual mill yield closer than any other rule — which is exactly why it serves as the yardstick the other rules are measured against.

## Bias comparison

| Rule | Basis | Small logs | Large logs | Where used |
| --- | --- | --- | --- | --- |
| Doyle | formula | strong underestimate (overrun often +30–100%) | mild overestimate | US South hardwood trade |
| Scribner (C) | diagram | slight underestimate | conservative | US West, public timber |
| International ¼" | kerf/taper model | ≈ actual yield | ≈ actual yield | benchmark everywhere |

Overrun — actual yield minus rule estimate — is therefore mostly a statement about the rule, not about the mill.

## Which rule should you quote?

Whichever one the contract says — but always name it next to the price, because "36" means nothing until you say Doyle. Keep one rule for buying and one historical overrun figure for your own mill, and the two stay reconciled. Metric-side scaling (Huber, Smalian, JAS) is a different family: [Log volume (Huber/Smalian)](https://nestingcalc.com/log-volume-calculator/) scales true volume, [JAS Log Scaling: The Japanese Agricultural Standard Explained](https://nestingcalc.com/guides/jas-log-grading-standard/) covers JAS, [Sawmill Recovery Rate: Benchmarks and How to Improve Yours](https://nestingcalc.com/guides/sawmill-recovery-rate/) the recovery/overrun bookkeeping.

[Log volume (Huber/Smalian)](https://nestingcalc.com/log-volume-calculator/) [Open the linear cutting calculator](https://nestingcalc.com/linear-cutting-calculator/)

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