Estimate the board feet of lumber in a log using the three common log rules: Doyle, Scribner and International ¼-inch. Enter the small-end diameter and log length.
How to measure a log
- Measure the diameter at the small end, inside the bark, in inches.
- Measure the log length in feet. Logs are usually cut in 8, 10, 12 or 16 ft lengths plus a few inches of trim.
The three log rules
Doyle
BF = (D − 4)² × L ÷ 16. Common in the eastern and southern US. It underestimates small logs and can overestimate very large ones.
Scribner
Based on diagrams of boards in a log. This calculator uses the common formula approximation BF = (0.79D² − 2D − 4) × L ÷ 16, so results can differ slightly from printed Scribner tables. Widely used in the western US.
International ¼-inch
Calculated in 4-ft sections with a ½-inch taper per section and a ¼-inch saw kerf. It is generally considered the closest to actual sawn yield.
Example
A 16-inch diameter, 16-ft log: Doyle = (16 − 4)² × 16 ÷ 16 = 144 BF. International ¼” ≈ 180 BF. Scribner (formula) ≈ 166 BF. The same log can be valued very differently, so always ask which rule a buyer uses.
Log rules vs. lumber board feet
Log rules estimate how much lumber a sawmill can cut from a log after losses for bark, slabs and saw kerf. For sawn boards, use our board foot calculator.
Frequently asked questions
Which log rule should I use?
Use the rule your buyer or mill uses. For an estimate closest to real yield, use International ¼-inch.
What is MBF?
MBF means 1,000 board feet. Log and timber prices are often quoted per MBF.