Doyle Log Rule Guide
What It Measures
The Doyle log rule is a classic board-foot estimator. It converts log diameter and log length into an expected sawn volume. The method is simple. It is also quick. That makes it useful for field checks, buying notes, and small sawmill planning.
How the Rule Works
The rule uses the small-end diameter inside bark. It also uses log length in feet. Four inches are removed from the diameter. This allowance represents slab and edging loss. The remaining diameter is squared. The value is then adjusted by log length.
Planning Controls
This calculator adds practical planning controls. You can enter quantity, bark allowance, trim loss, defect deduction, waste allowance, and price per board foot. These inputs help you move from raw scale to usable value. They also show how each deduction changes the final estimate.
Understanding the Result
The result area reports gross Doyle volume, grade-adjusted volume, defect loss, waste loss, usable board feet, and estimated value. It also shows converted diameter and length. These details are useful when measurements come from mixed field notes.
Why Diameter Matters
The chart shows how board feet change as diameter changes. This is important because the formula squares the adjusted diameter. A small change in diameter can make a large change in volume. Bigger logs gain board feet quickly. Very small logs may return little volume because of the four-inch allowance.
Accuracy Notes
Use the output as an estimate, not a final sale contract. Real recovery depends on taper, sweep, rot, kerf, sawing pattern, log grade, and local scaling rules. The Doyle rule can understate some large logs and overstate some small situations. Local mills may also use their own rounding methods.
Best Practice
For better decisions, measure carefully. Use the small-end diameter inside bark when possible. Record length after trimming. Apply defect deductions honestly. Compare several logs in a batch. Export the result when you need a simple record for buyers, sellers, or production notes.
Learning Value
The example table gives sample field entries. It helps users test the calculator before using real values. The formula section shows every main equation. The usage section explains the workflow. It supports faster audits during timber purchase discussions and planning. Together, these sections make the tool clear for students, landowners, foresters, and sawmill operators.