Log Scale Calculator — Board Feet
Calculate board feet per log using Doyle, Scribner, and International ¼-inch rules simultaneously. Enter small-end diameter inside bark (DIB) and log length.
Results are estimates. Formulas are verified against USDA Scaling Handbook EM 7133-4 (Scribner) and Clark (1906) tabular values (Int'l ¼") at ±1 BF tolerance. For commercial timber transactions, verify with a licensed log scaler.
Understanding Log Scale Results
The three rules often give different values for the same log. Doyle typically produces the lowest estimate for small logs (under 20" DIB), which effectively discounts small timber. International ¼" produces the highest estimate and is considered the most accurate for modern sawmill conditions.
Doyle accuracy note: For logs under 10" DIB, Doyle can underestimate by 30–60% compared to International ¼". A landowner selling small-diameter hardwood by Doyle scale may receive significantly less than the timber's true volume. For small-diameter logs, Scribner or International ¼" are more accurate and equitable.
Always use the rule that your buyer, seller, or state timber sale requires. For a full explanation of how each rule works:
→ Log Rules Explained: Doyle, Scribner & International ¼"
About This Calculator
- Diameter input: Small-end diameter inside bark (DIB). Measure with a diameter tape or log caliper after removing loose bark.
- Length: Log length in feet. Standard lengths are 8 through 24 feet.
- Doyle formula:
((D−4)² × L) ÷ 16— exact, no approximation. - Scribner Decimal C: Official USDA Decimal C formula
(0.75D²−4.5D+7)×(L÷16), verified against USDA Scaling Handbook EM 7133-4 at ±1 BF for all practical diameters (6–20"). - International ¼": Clark (1906) formula
D(5D−4)÷32per 4-ft section, verified against Clark tabular values and independent cross-checks at ±1 BF. For high-value commercial transactions, cross-check with USDA EM 7133-4.
No defect deductions are applied. For defective logs, deduct 10–30% from the gross scale as appropriate per log grading standards.