Doyle Board Feet Calculator
Estimate log scale quickly using the Doyle log rule. Enter the small-end diameter inside bark, the merchantable log length, and the number of logs to calculate board feet per log and total board feet. A live chart also shows how estimated volume changes across common log lengths for your selected diameter.
Expert Guide to the Doyle Board Feet Calculator
A doyle board feet calculator is a practical forestry tool used to estimate the volume of lumber that can be sawn from a log. The term “board foot” means a unit of wood volume equal to a board that is 1 inch thick, 12 inches wide, and 12 inches long. In timber buying and selling, however, a board-foot estimate is not obtained by physically cutting every log into boards. Instead, log rules are used. The Doyle rule is one of the oldest and most recognized log rules in the United States, especially in hardwood-producing regions.
The calculator above uses the classic Doyle formula:
where diameter is the small-end diameter inside bark in inches, and length is the log length in feet.
This formula assumes a substantial slab loss and saw kerf, which is one reason the Doyle rule often gives lower scale values for small logs than some other log rules. Even so, it remains widely referenced in stumpage sales, mill scale discussions, timber appraisals, and traditional forest management records. If you work with hardwood logs, portable sawmills, farm woodlots, or timber sales in regions where buyers still quote Doyle scale, understanding the calculator can help you evaluate volume more confidently.
How the Doyle rule works
The core idea behind the Doyle rule is simple: estimate the amount of square cant that can be sawn from a round log, then convert that into board feet. In the formula, 4 inches are subtracted from the small-end diameter to account for slabs, edgings, and saw kerf. The adjusted diameter is then squared, reflecting the usable cross-sectional area. Finally, the result is multiplied by log length and divided by 16 to convert to board feet.
Because of that 4-inch deduction, the rule is conservative for smaller logs. For example, if a log scales 8 inches inside bark at the small end and is 12 feet long, the Doyle estimate is:
- Adjusted diameter: 8 – 4 = 4
- Square of adjusted diameter: 4 × 4 = 16
- Multiply by length: 16 × 12 = 192
- Divide by 16: 192 ÷ 16 = 12 board feet
Now compare that with a 16-inch log of the same length:
- Adjusted diameter: 16 – 4 = 12
- Square: 12 × 12 = 144
- Multiply by length: 144 × 12 = 1,728
- Divide by 16: 108 board feet
That steep increase explains why diameter is such a powerful driver of sawlog volume. A modest increase in scaling diameter can create a much larger increase in board feet than many landowners expect.
When to use a doyle board feet calculator
You should use a doyle board feet calculator whenever you need a fast estimate based on logs that are likely to be scaled by the Doyle rule. Common situations include:
- Timber sale planning: Landowners can estimate sale volume before requesting bids.
- Mill delivery checks: Truckload logs can be reviewed against scale tickets.
- Portable sawmill planning: Sawyers can compare expected lumber yield against project needs.
- Forest inventory work: Consulting foresters can convert representative logs into estimated board-foot volume.
- Educational use: The formula is ideal for learning how diameter and length influence log scale.
If your region uses Scribner or International 1/4-inch log rules more often, this calculator is still useful for comparison. Just remember that the same physical log can produce different board-foot estimates depending on the chosen rule.
Interpreting your calculator result
After you enter the small-end diameter, log length, and number of logs, the calculator returns:
- Board feet per log based on the Doyle formula
- Total board feet for the number of logs entered
- Approximate lumber equivalent expressed in standard 8-foot 1×12 boards for easy visualization
This result is an estimate of log scale, not a guarantee of finished lumber yield. Actual output depends on sweep, taper, crook, defect, rot, grade, mill equipment, saw kerf, edging practice, and product dimensions being sawn. A straight, high-grade walnut log and a low-grade red oak log could scale similarly in board feet yet differ greatly in value and actual usable output.
Comparison table: Doyle volume by diameter and length
The table below uses the Doyle formula directly. These figures are representative values often checked by landowners and sawyers when estimating volume on common sawlog sizes.
| Small-end diameter inside bark | 8 ft log | 10 ft log | 12 ft log | 16 ft log |
|---|---|---|---|---|
| 12 in | 32 bf | 40 bf | 48 bf | 64 bf |
| 14 in | 50 bf | 62.5 bf | 75 bf | 100 bf |
| 16 in | 72 bf | 90 bf | 108 bf | 144 bf |
| 18 in | 98 bf | 122.5 bf | 147 bf | 196 bf |
| 20 in | 128 bf | 160 bf | 192 bf | 256 bf |
Notice how volume growth accelerates as diameter rises. That is why a stand with fewer but larger trees can hold significant board-foot value. It is also why accurate diameter measurement matters so much in a timber appraisal.
How Doyle compares with other log rules
Three major log rules are commonly discussed in the eastern and central United States: Doyle, Scribner, and International 1/4-inch. While all aim to estimate sawn lumber recovery, they are based on different assumptions. The Doyle rule is older and simpler, but it tends to understate small-log volume. Scribner is also diagram based and can differ materially on medium logs. International 1/4-inch usually tracks actual sawn recovery more closely because it incorporates taper and a more realistic kerf allowance.
| Log rule | General behavior | Most common practical takeaway |
|---|---|---|
| Doyle | Conservative on small logs due to 4-inch deduction | Often favored in markets where buyers and sellers are accustomed to traditional hardwood scaling |
| Scribner | Moderate estimate based on board diagrams | Can be closer than Doyle on some mid-size logs, but still differs from actual mill output |
| International 1/4-inch | Designed to reflect taper and 1/4-inch kerf more realistically | Often considered the most consistent estimate of actual lumber recovery across a range of diameters |
As a practical example, extension forestry publications commonly note that Doyle significantly discounts small logs. This means a woodland owner with many 10 to 14 inch logs may receive a notably lower board-foot scale under Doyle than under International 1/4-inch. The exact difference depends on diameter, length, and local scaling conventions, but the directional effect is well established in forestry education.
Step-by-step instructions for accurate use
- Measure the small end: Use the small-end diameter inside bark, not outside bark. Bark thickness can materially affect the estimate.
- Use merchantable length: Measure the portion of the log that can reasonably be sawn into products.
- Exclude obvious defects if needed: The calculator gives gross scale. Heavy rot, forks, severe sweep, and breakage may reduce merchantable volume.
- Enter the number of similar logs: If several logs are roughly alike, the quantity field can produce a quick total.
- Review the chart: The chart helps you see how much volume would change if lengths were bucked differently at the same diameter.
Common mistakes to avoid
- Using diameter outside bark: This usually inflates volume compared with proper scaling practice.
- Measuring the large end: The Doyle rule uses the small-end scaling diameter.
- Applying the rule to very small logs: Logs near the lower end of sawlog diameter can produce very low Doyle values and may not reflect practical use.
- Ignoring defects: Gross scale is not the same as net saleable value.
- Confusing board feet with cubic feet: They are different units and should not be interchanged without conversion.
Why local market practice matters
In timber sales, the “right” calculator is often the one that matches your local market. If local mills buy veneer and grade hardwood on Doyle scale, using Doyle lets you compare your estimate with the language buyers actually use. If your area quotes International 1/4-inch for most sawlogs, a Doyle estimate may be less relevant for negotiations. Always ask buyers what log rule they use, whether the scale is gross or net, and how defects are deducted.
In other words, the calculator is technically simple but commercially important. Two buyers can look at the same truckload and quote different board-foot numbers because they are using different scaling systems. That does not necessarily mean either person is wrong. It means the underlying rule is different. Clear communication avoids costly misunderstandings.
How board feet relates to timber value
Board feet measure volume, not price. To estimate value, you still need a market rate per thousand board feet, usually written as MBF. For example, if your total is 1,250 Doyle board feet and a buyer quotes $650 per MBF, the rough gross value estimate would be:
1.25 × $650 = $812.50
That is still only a rough estimate. Actual sale value depends on species, grade, defects, trucking, market timing, contract terms, and whether the logs are sold roadside, delivered, or standing stumpage. Premium veneer logs can be worth many times more than ordinary sawlogs of the same board-foot volume.
Authoritative forestry references
For more detail on log rules, timber measurement, and forest products, review these reliable sources:
Final takeaway
A doyle board feet calculator is most useful when you need a fast, regionally familiar sawlog volume estimate. It is especially relevant in hardwood timber markets where the Doyle rule remains common. The formula is straightforward, but the implications are important: diameter matters more than many people expect, small logs are discounted more heavily than under some other rules, and actual value depends on much more than volume alone.
If you are comparing bids, planning a timber harvest, evaluating a portable sawmill project, or simply learning how logs are scaled, this calculator gives you a practical starting point. Use it for fast estimates, then confirm the log rule, deduction method, and grading standards used in your local market before making pricing or harvest decisions.