Board feet in a log

Measure the diameter inside the bark at the small end and the length, then read the table — or use the log calculator.

Doyle (most mills quote it) subtracts a fixed 4″ slab allowance, which punishes small logs. International 1/4″ models real recovery with taper and a 1/4″ kerf, and runs closer to what a band mill actually yields.

Why three rules exist at all

Every log rule is a nineteenth-century argument frozen into arithmetic. Edward Doyle published his rule around 1825, and its harshness on small logs made it a permanent favorite of log buyers. J. M. Scribner answered in 1846 by literally drawing 1″ boards inside circles of every diameter and counting them. The International rule came last (Judson Clark, 1906) — the only one built from actual mill studies, accounting for taper and kerf — which is why foresters call it the accurate one and why sellers wish everyone used it.

The practical upshot: the same log can "contain" three different quantities of lumber depending on whose century-old math the deal uses. Agree on the rule before agreeing on the price — on a 12″ log, Doyle pays the seller roughly 20% less than International for identical wood.

Doyle scale

International 1/4″ scale

Computed from the scale formulas; printed mill tables round a few BF either way. Yield still depends on the sawyer, the log's defects, and how thin you saw.