Enter the diameter at the small end of the log, inside the bark, and the log length. The calculator shows the board feet under the Doyle, Scribner and International ¼ inch log rules, and the value if you enter a price.
Value
| Log rule | Per log | All logs |
|---|
Log rules estimate the lumber a sawmill can cut. Real yield depends on the log, the saw and the sawyer.
How to measure a log
- Measure the diameter across the small end, inside the bark, in inches. If the end isn’t round, average the widest and narrowest measurements.
- Measure the length in feet. Sawmills usually buy logs in set lengths, such as 8, 10, 12 or 16 feet.
The three log rules
- Doyle: board feet = (diameter − 4)² × length ÷ 16. Simple, but it underestimates small logs and overestimates very large ones.
- Scribner: based on drawings of boards in a log circle. The calculator uses the common formula version: (0.79 × diameter² − 2 × diameter − 4) × length ÷ 16.
- International ¼ inch: works in 4 ft sections and allows for taper and a ¼ inch saw kerf. It’s usually the closest to what a modern mill actually cuts.
Which rule is used depends on the region and the buyer, so ask before you sell.
Worked example
A log 16 inches across the small end and 16 ft long:
| Log rule | Board feet |
|---|---|
| Doyle | 144 |
| Scribner (formula) | 166 |
| International ¼ inch | 181 |
The same log can be “worth” quite different amounts depending on the rule, which is why it matters which one a buyer uses.
Timber value
Timber is usually priced per thousand board feet, written MBF. Value = board feet ÷ 1,000 × price per MBF. For example, 720 board feet at $400 per MBF is $288. Prices vary a lot by species, grade and region.
Frequently asked questions
How do I calculate board feet in a log?
Measure the small-end diameter inside the bark and the length, then apply a log rule. For Doyle: (diameter − 4)² × length ÷ 16.
Which log rule is most accurate?
The International ¼ inch rule is generally the closest to actual mill output. Doyle gives low numbers for small logs.
How many board feet are in a 16 inch log?
For a 16 ft log, about 144 board feet by Doyle, 166 by Scribner and 181 by International ¼ inch.
Why measure inside the bark?
Bark doesn’t make lumber, and log rules are built on the diameter of the wood itself.
Why measure the small end?
Log rules use the small end because that’s the size of the boards that can run the full length of the log.
Results are estimates. Actual yield depends on the log, the saw and the sawyer. See How We Calculate for the formulas we use.
