October 18, 2026

Log Scaling Guide: Doyle, Scribner and International Rules Compared

Every log deal starts with a number, and this log scaling guide exists because that number is not a fact — it is an estimate produced by a rule, and the three rules in common use give three different answers for the same log. A 16-inch, 16-foot log scales at 180 board feet by the International 1/4 rule, 160 by Scribner Decimal C, and 144 by Doyle. At $500 per thousand board feet, that spread is $72 versus $90 for identical wood. Whether you are buying logs, selling logs or milling your own, the rule named in the deal matters as much as the price.

Scaling is the measurement of a log's sound volume, taken at the small end, inside the bark, and converted to board feet by a log rule. If you work in the woods, the equipment side of the trade sits on places like the forestry and logging equipment listings on Lumber Lookup, where harvesters, forwarders and trucks exchange hands. This guide covers the other side: how the wood itself gets counted before any money moves.

How Scaling Works Before the Rules Apply

Whatever rule you use, the field work is the same. Measure the diameter at the small end of the log, inside the bark. For an out-of-round log, take two measurements at right angles and average them, then round down to the last full inch. Measure length to the last full foot, ignoring fractions. Gross scale is the rule's volume for that diameter and length. Net scale subtracts deductions for visible defect — rot, shake, sweep, crook and splits — because a rule assumes a sound log and real logs are not always sound.

Two clarifications prevent most arguments. First, board feet in a log are potential lumber, not guaranteed lumber: kerf, slabs and edging losses are already baked into the rules, imperfectly. Second, scaling is not the same as tallying sawn lumber. Once a log is boards, you measure the boards themselves, which the companion piece on how to calculate board feet covers board by board.

The Doyle Rule: Simple, Old and Hard on Small Logs

The Doyle rule is the oldest of the three and the simplest to compute in the field: subtract 4 inches from the diameter, divide by 4, square the result, and multiply by the length in feet. In symbols, board feet = ((D − 4) ÷ 4)² × L. A 16-inch, 16-foot log: ((16 − 4) ÷ 4)² × 16 = 3² × 16 = 144 board feet — matching the table below.

That formula carries a fixed 4-inch slabbing allowance regardless of log size, which is why Doyle behaves so unevenly. The slab waste on a 10-inch log is not the same fraction of the log as on a 30-inch log, but Doyle charges both the same 4 inches. As Virginia Cooperative Extension's forest landowner guide (publication 420-085) puts it, Doyle underestimates small logs and overestimates large ones, and because nearly all logs in the eastern hardwood trade run under 30 inches, in practice Doyle simply under-scales. Doyle remains common in log buying across the East and South and in much of the hardwood trade — which is exactly why sellers of small logs need to understand it before they agree to it.

The Scribner Rule: A Diagram, Not a Formula

Scribner, developed around 1846, is a diagram rule: its volumes were derived by drawing 1-inch boards, with 1/4 inch left between them for saw kerf, inside circles of each diameter and counting how much lumber fit. There is no algebraic formula to memorise; you read a table or a scaling stick. Scribner Decimal C, the version in everyday use, rounds each volume to the nearest 10 board feet (392 becomes 390), which speeds up tally work at the landing.

The diagram origin explains Scribner's behaviour. Because it is drawn rather than calculated, it makes no allowance for log taper, and Virginia Extension notes it typically underestimates — particularly long logs, where the big end holds wood the small-end diagram never sees. Scribner is the standard across much of the West and is used by many public agencies, so anyone buying western logs or selling into western mills will meet it constantly. For the grade side of what those scaled logs become, the companion explainer on lumber grades picks up where scaling leaves off.

The International 1/4 Rule: Built on Kerf and Taper

The International rule is the youngest and the most deliberately engineered. The 1/4-inch version dates to 1906 and is built on a mathematical formula rather than diagrams: it allows for a 1/4-inch saw kerf, shrinkage, a slab allowance that varies with diameter, and — uniquely among the three — a fixed taper allowance of 1/2 inch per 4 feet of log length. Virginia Extension calls it the most consistent of the rules and notes it is often used as the basis of comparison for the others.

That engineering shows in the numbers. On small logs International scales well above Doyle; on very large logs Doyle eventually overtakes it, because Doyle's overscaling grows while International tracks realistic yield. International is the common rule in New England and parts of the Northeast and is the usual reference when a deal needs converting from one rule to another. Its one caveat is the kerf assumption: it was built for 1/4-inch-kerf saws, so a thin-kerf band mill will saw out more than the scale — the overrun belongs to whoever owns the log at milling time.

The Same Log, Three Numbers: A Worked Comparison

The table below uses the comparison published in Virginia Extension's guide for 16-foot logs. Read across any row and you are looking at three different paydays for one log.

Two lessons jump out. First, the gap is brutal at small diameters: an 8-inch log scales two and a half times as much wood on International as on Doyle, so at small sizes the rule is the price. Second, the three rules converge near 24–30 inches, which is why Doyle's defenders — usually buying large timber — can honestly call it fair while sellers of small logs honestly call it theft. A fuller walk-through of the same comparison, including value at a set price per thousand, appears in Woodworker's Journal's log-rules series.

Which Rule Should Your Deal Use?

Start with local custom, because the market you sell into already has one. If every mill in your county buys Doyle, quoting International volumes will not win arguments — but it should change the price per thousand you accept, since the same wood is being counted smaller. That conversion mindset is the practical heart of this log scaling guide: rule and rate are a package, and either can move to make a deal equivalent.

Practical steps before any log changes hands:

• Name the rule in writing. "Sold by the thousand" is incomplete; "sold by the thousand, Doyle scale, net of defect" is a deal.
• Agree on defect deductions. Who scales, and how sweep, rot and shake are deducted, should be settled before the truck loads, not at the mill gate.
• Scale a sample load yourself. A scaling stick costs little and an hour spent checking one load against the buyer's tally teaches more than any guide.
• Watch the diameter mix. If your sale is heavy in 10–16 inch logs, the rule choice swings total volume by 20 percent or more; on uniform big timber it matters far less.

If you are the one selling, remember the volume you are paid for is only half the transaction — presentation, species, grade and access all move the rate. When the logs are gone and it is equipment doing the earning, or when you are ready to move timber or machinery on, list it where the trade looks: sell through Lumber Lookup and keep the forestry and logging equipment listings in view for the machines that do the hauling.

Conclusion

A log scaling guide comes down to one habit: never accept a volume without asking which rule produced it. Doyle is simple and traditional but punishes small logs; Scribner is the western and agency standard, drawn rather than calculated, and blind to taper; International 1/4 is the most consistent because it was engineered around kerf and taper. Learn the rule your market uses, convert before you negotiate, and put the rule in the deal in writing. Then head to LumberLookup.com — scale your timber fairly, and browse the forestry and logging equipment that turns scaled logs into sold lumber.