Doyle vs Scribner vs International: Which Log Rule Should You Use?

You cut a log with a 16 inch small-end diameter and 16 feet long. Doyle says 144 board feet. Scribner says about 166. International 1/4 inch says about 200. Same log, three answers, and the gap is wide enough to change what you get paid.

That spread is not an accident. Each log rule was built with different assumptions, and each one leans a certain way. If you are buying or selling logs, the rule on the ticket matters as much as the price per thousand.

What a log rule actually is

A log rule is a formula, or an old lookup table, that estimates how many board feet of lumber a mill can saw out of a log. You feed it the small-end diameter in inches and the log length in feet. It hands back a board foot count.

It is only an estimate. A board foot is 144 cubic inches of lumber, but a round log is not a stack of boards. You lose wood to the saw kerf, to slabs off the round sides, and to taper. Log rules try to guess what survives after all that waste. Some guess low, some guess high, and that bias is baked in.

If you want to skip the pencil work, run your numbers through the log scale calculator and compare all three at once. But you should still know what each rule is doing under the hood.

Doyle: undercounts small logs

Doyle is the most common rule in the eastern and southern US, mostly because sawmills like it. It subtracts 4 inches from the diameter for slab waste before it figures anything, then squares the result. That 4 inch chunk hits small logs hard.

On a 6 or 8 inch log, Doyle throws away a huge share of the wood on paper, so it reads low. The log gives up more lumber than Doyle claims, and the mill pockets the difference. On big logs the bias shrinks and Doyle gets closer to reality.

If you are selling small logs scaled by Doyle, you are leaving money on the table. Know that going in.

International 1/4 inch: the most accurate

International 1/4 inch was designed to model the actual sawing process. It accounts for a 1/4 inch saw kerf, figures the log in 4 foot sections, and even builds in taper. Of the three, it tracks real mill yield the closest across every log size.

Foresters and the US Forest Service lean on International because it is honest. It does not flatter the mill or the seller. If you want the number that best predicts what actually comes off the saw, this is the one.

The catch is it is more work to calculate by hand, which is part of why mills stuck with Doyle.

Scribner: sits in the middle

Scribner is an old diagram rule. Somebody drew boards inside circles and counted them. It ignores taper and assumes a thicker kerf than modern saws use, so it reads a little low, but nowhere near as low as Doyle on small logs.

Scribner is standard across a lot of the western US and shows up in government timber sales. For most log sizes it lands between Doyle and International, which is exactly what our sample log shows.

The three rules side by side

Here is that 16 inch by 16 foot log, plus a couple more sizes so you can see how the gap moves.

Log (small-end dia x length)	Doyle	Scribner	International 1/4"
8 in x 16 ft	16	31	43
12 in x 16 ft	64	86	107
16 in x 16 ft	144	166	200
20 in x 16 ft	256	272	320

Look at the 8 inch row. Doyle says 16 board feet while International says 43. Doyle is reading less than half the real yield on that small log. By 20 inches the three rules are much closer together, which is the whole story: Doyle punishes small logs and comes back to earth on big ones.

Which one should you use

Use the rule your mill buys by. That is the practical answer. If the mill down the road scales on Doyle, argue about price all you want, but the Doyle number is what fills out the ticket. Fighting the rule after the fact gets you nowhere.

Before you haul anything, ask which rule the buyer uses and run your logs through both that rule and International 1/4 inch. If the mill is on Doyle and your logs are small, International tells you how much yield you are actually giving up, and that is your leverage on price.

For your own planning, cruising your woodlot, or estimating a standing tree, International 1/4 inch is the number to trust. It is the closest thing to the truth about what the saw will produce.

Once you know your board foot totals, figure out what it is worth and check whether Doyle scaling cost you anything worth negotiating over.