SawTallyOpen the appHow many board feet are in a log?
Estimating log volume before you saw · last checked September 26, 2026.
A log's board-foot volume is an estimate from a "log rule" — a formula that predicts how much lumber is inside the log from its small-end diameter (measured inside the bark) and its length. The three common rules disagree on purpose, and the gap is widest on small logs.
The three log rules
| Rule | How it behaves | Where it's common |
|---|---|---|
| Doyle | ((D − 4) ÷ 4)² × L — subtracts 4″ for slab waste then squares, so it under-scales small logs and over-scales big clean ones. | Eastern US |
| Scribner Decimal C | A diagram rule rounded to the nearest 10 bd ft. Middle of the road. | Western US |
| International 1/4-inch | Accounts for taper and a 1/4″ kerf — most accurate to real sawn yield. | Research / most accurate |
A worked example
Take a 16-inch, 12-foot log. Doyle gives ((16 − 4) ÷ 4)² × 12 = 3² × 12 = 108 board feet. The International rule reads higher because it doesn't throw away as much to the "minus 4" waste allowance. On a 10-inch log the split is even more dramatic — Doyle can read less than half of International.
Diameter and length matter more than you'd think
- Measure the small end, inside the bark — that's what every rule expects.
- Round length down to the usable log length; a foot of trim doesn't make lumber.
- Board-foot volume rises with the square of diameter — a 20″ log holds far more than twice a 10″ log of the same length.
Scale any log in one tap
SawTally's free calculator runs Doyle, Scribner and International side by side from your log's diameter and length — so you can quote from the rule your buyer expects and see the others at a glance. No sign-up.
Open the free log-scale calculator →
Log rules are estimates from published forestry formulas and differ from actual sawn yield. Confirm the rule and figures your buyer uses. Not financial advice.