How to Use This Calculator
Enter the small-end diameter of the log in inches, measured inside the bark. For most logs, subtract 1 to 2 inches from your outside-bark measurement to estimate inside-bark diameter. Enter the log length in feet. Set the number of logs to calculate a total for a pile or load. The result shows Doyle board feet per log and the total for the batch, plus the MBF (thousand board feet) value for pricing timber. Use the quick-pick buttons to load common log sizes. The Doyle rule is widely used in the eastern US; confirm with your buyer or sawmill which scale they use before selling timber.
How the Doyle Rule Formula Works
Doyle Rule: Board Feet = ((D − 4) ÷ 4)² × L. Where D is the small-end diameter inside the bark in inches, and L is the log length in feet.
Example: a log with a 14-inch small-end diameter (inside bark) and 12-foot length. Step 1: (14 − 4) ÷ 4 = 2.5. Step 2: 2.5² = 6.25. Step 3: 6.25 × 12 = 75 board feet per log.
For comparison, the same log under the International 1/4-inch Rule scales at approximately 95 board feet. The Doyle rule underestimates small logs (under 16 inches), which is why buyers in timber markets often prefer it. For logs 16 inches and above the two scales produce closer results.
Log Scaling Tips
Always know which scale applies before signing a timber contract. Doyle, Scribner, and International produce meaningfully different board foot counts on the same log. A timber buyer quoting $400 per MBF under International is offering the same money as $300 per MBF under Doyle for most mid-sized hardwood logs. Get quotes on the same scale to compare.
Measure at the small end. The Doyle rule and most log rules measure at the narrowest end of the log, inside the bark. Do not average both ends. Do not include bark. A loose tape over the bark can add 1 to 3 inches to your reading — this matters on small-diameter logs where the formula is already biased low.
Length matters for grade. Hardwood sawyers cut for the longest, clear boards possible. A 16-foot log that can be sawn into two 8-foot clears is often worth less than a single 16-foot clear board. When logging high-value species (walnut, oak, cherry), discuss length and grade requirements with your buyer before felling.
What to Buy
If you are selling standing timber: get at least two bids from licensed timber buyers. Prices vary widely by species, log quality, and proximity to mills. State forestry agencies often maintain lists of licensed buyers and can advise on fair market rates for your region.
If you are buying logs for a portable sawmill: the Doyle scale gives you a price baseline, but actual yield depends on log quality, straightness, and species. High-quality hardwood logs often yield 10 to 20% more board feet than the Doyle scale predicts because Doyle was designed conservatively around mill waste in older equipment. Factor in your sawing costs ($0.25 to $0.60 per board foot) when evaluating log purchases.
Frequently Asked Questions
What is the Doyle rule for log board feet? +
The Doyle rule is a log scaling formula that estimates the board feet of lumber that can be sawn from a round log: BF = ((D - 4) ÷ 4)² × L. D is the small-end diameter inside the bark in inches; L is the log length in feet. It was developed in the 1800s and remains the most widely used log scaling method in the eastern US and South. The Doyle rule is known to underestimate small logs (under 16 inches) and overestimate large logs.
What is the difference between Doyle, Scribner, and International scales? +
All three estimate saw log board feet, but they use different formulas and produce different numbers. Doyle is the simplest and most common in the South and East. It underestimates small logs, which benefits buyers. Scribner uses a printed table based on diagram-derived values and is common in the West and Midwest. The International 1/4-inch Rule is the most accurate formula, accounting for taper and kerf loss. The rule used in a timber sale must be specified in the contract.
What diameter do I measure for the Doyle rule? +
Measure the small-end diameter inside the bark, in inches. Inside the bark means you subtract the bark thickness. For most logs, subtract 1 to 2 inches from the outside diameter measurement to get the inside-bark diameter. Some states and log buyers measure to the nearest inch; others measure to the nearest half-inch. Confirm the measurement method with your buyer or sawmill before scaling.
How accurate is the Doyle rule? +
The Doyle rule is notoriously inaccurate for small logs. For logs under 16 inches in diameter, the formula underestimates actual yield by 20 to 40%. For logs 16 to 20 inches, it is close to accurate. For logs over 24 inches, it overestimates. Because small logs are undervalued under Doyle, buyers prefer it; sellers sometimes negotiate to use Scribner or International on small-diameter timber. Always know which scale applies to your sale.
What is a MBF? +
MBF stands for thousand board feet. Timber is bought and sold in MBF because individual log board foot counts are small numbers. A mature white oak might scale at 80 board feet per log; you need many logs to reach the volumes buyers want. Timber prices are quoted in dollars per MBF. A standing timber sale at $300 per MBF and a volume of 50 MBF produces a gross payment of $15,000. Convert your board foot total to MBF by dividing by 1,000.
Can I use the Doyle rule for all log species? +
Yes — the Doyle rule is species-neutral. It estimates the volume of lumber that a log of any species can produce, not the value. Value depends on species, grade, and market conditions. The same log scaled at 80 board feet under Doyle might be worth $40 as low-grade pine or $240 as prime white oak. The rule just tells you how many board feet the log will yield; the species and quality determine the price per board foot or per MBF.
Does log length affect board feet linearly? +
Yes. The Doyle formula is linear in length: doubling the log length doubles the board feet. A 12-inch diameter, 8-foot log scales at 32 board feet; the same diameter at 16 feet scales at 64 board feet. Most hardwood sawlogs are cut in 8-foot, 10-foot, 12-foot, 14-foot, and 16-foot lengths. Longer logs mean fewer joints and more flexibility in cutting, which often commands a slight premium.
