Board Feet Calculator For Logs

Estimate log volume in board feet using common North American log rules. Enter log diameter, length, and the desired scaling rule to compare Doyle, Scribner, International 1/4-inch, and a simple cubic-foot conversion.

Estimated Results

Note: Log rules are estimates. Actual sawn lumber output depends on taper, sweep, defects, taper deduction, trim, saw kerf, and mill practices.

Expert Guide: How a Board Feet Calculator for Logs Works

A board feet calculator for logs helps foresters, sawyers, woodland owners, buyers, and hobby mill operators estimate how much lumber a round log may yield. In practical terms, a board foot is a unit of lumber volume equal to a board that is 1 inch thick, 12 inches wide, and 12 inches long. That equals 144 cubic inches, or 1/12 of a cubic foot. When you are dealing with standing timber or bucked logs, however, you usually do not estimate output by measuring every board. Instead, you use a log rule, which converts log dimensions into an expected board-foot yield.

This matters because two logs with the same outside diameter and length may not produce the same amount of lumber once bark, slab loss, taper, edging, defects, and saw kerf are considered. That is why board-foot estimates for logs are not the same thing as pure geometric volume. A true board feet calculator for logs applies a recognized rule, such as Doyle, Scribner, or International 1/4-inch, each of which makes different assumptions about recoverable lumber.

What Inputs Matter Most?

At minimum, a useful calculator needs two measurements: small-end diameter and merchantable log length. Most professional scaling references emphasize measuring the smaller end because it is the limiting cross section for lumber recovery. Some mills use diameter inside bark, while field estimates often rely on outside bark and then make deductions. If your buyer or mill provides a scaling sheet, always match their method so your estimate is comparable.

Core inputs used in board-foot estimates

• Small-end diameter: Typically measured in inches. Even a 1-inch difference can materially change estimated yield.
• Log length: Usually measured in feet. Standard sawlog lengths often include trim allowances.
• Log rule selected: Doyle, Scribner, and International 1/4-inch can produce noticeably different results from the same log.
• Number of logs: Helpful when estimating a truckload, log deck, or thinning operation.
• Species and grade notes: Not always used in the raw board-foot calculation, but critical for pricing and utilization.

Understanding the Major Log Rules

North American forestry and sawmilling still rely on several historic log rules. A calculator is only as useful as the rule chosen for the transaction you are evaluating. Here is a practical summary of the big three.

Doyle Rule

The Doyle rule is widely recognized in many hardwood markets, especially in parts of the eastern and central United States. It is easy to calculate, but it is also known to underestimate smaller logs. That underestimation can become substantial when diameters are low. A common form of the Doyle formula is:

Doyle BF = ((D – 4)² × L) / 16

In this formula, D is small-end diameter in inches and L is log length in feet. Because the rule subtracts 4 inches before squaring, smaller logs can lose a large portion of their theoretical yield in the estimate.

Scribner Rule

The Scribner rule was developed from diagrams of boards sawed from logs. It generally produces values that differ less dramatically than Doyle on smaller logs, but it still does not perfectly match real-world recovery across all diameters. A common calculator approximation is:

Scribner BF = (0.79D² – 2D – 4) × (L / 16)

Scribner remains common in some western regions and timber transactions. It can be a practical benchmark for comparing standing timber appraisals or mill offers where the local market still references it.

International 1/4-inch Rule

The International 1/4-inch rule is often considered one of the more realistic traditional board-foot rules because it attempts to account for taper and saw kerf more systematically. This is why many foresters regard it as a better all-around estimate when comparing logs across a broader range of sizes. One accepted approximation used in calculators is:

International BF ≈ (0.199D² – 0.642D – 1) × (L / 4)

For many practical estimates, International 1/4-inch tends to track actual lumber output more consistently than Doyle, especially when log diameters are moderate rather than large.

Board Feet Versus Cubic Volume

Some users want a direct geometric estimate instead of a historical log rule. In that case, the calculator can convert a cylinder-like log volume into cubic feet and then into board feet by multiplying cubic feet by 12. This is useful for rough planning, biomass estimates, or educational comparisons, but it should not be confused with a mill scale rule. Pure cubic volume does not automatically account for bark, taper, slab loss, edging, defects, or kerf.

The simple geometric method for a round log approximation is:

1. Convert diameter from inches to feet.
2. Compute radius in feet.
3. Estimate cubic feet as π × radius² × length.
4. Convert cubic feet to board feet by multiplying by 12.

If you compare cubic conversion with Doyle or Scribner, you will usually see the cubic method produce a larger number because it reflects gross geometric volume, not sawn lumber recovery under a scaling rule.

Comparison Table: Estimated Board Feet by Log Rule

The table below shows how the same 16-foot log can scale differently depending on the rule used. These are calculator-based estimates using common formulas, rounded for readability.

Small-End Diameter	Doyle (16 ft)	Scribner (16 ft)	International 1/4 (16 ft)
12 inches	64 BF	86 BF	100 BF
16 inches	144 BF	166 BF	190 BF
20 inches	256 BF	272 BF	316 BF
24 inches	400 BF	403 BF	475 BF

The main takeaway is simple: the same physical log can have meaningfully different board-foot estimates depending on the rule. If you are pricing logs, planning portable milling output, or comparing buyer quotes, make sure all parties are using the same system.

Real-World Lumber Dimensions and Why They Matter

Another source of confusion is the difference between nominal and actual lumber size. For example, a nominal 2×4 is not actually 2 inches by 4 inches after drying and surfacing. This does not change the definition of a board foot, but it does affect how people mentally picture the amount of material represented by a board-foot estimate. Educational extension resources routinely note that nominal dimensions exceed actual finished dimensions because of shrinkage and planing.

Nominal Lumber Size	Typical Actual Size	Board Feet in an 8-foot Piece
1 × 6	0.75 in × 5.5 in	4 BF nominal basis
2 × 4	1.5 in × 3.5 in	5.33 BF nominal basis
2 × 6	1.5 in × 5.5 in	8 BF nominal basis
4 × 4	3.5 in × 3.5 in	10.67 BF nominal basis

These values are useful because they connect abstract board-foot estimates to likely lumber output. If your log estimate is 160 board feet, that does not mean you will get exactly thirty 2×4×8 boards. Milling decisions, edging, defects, target dimensions, and drying degrade all shape the final tally.

How to Measure a Log for Better Accuracy

Field measurement tips

• Measure the small end of the merchantable log, not the butt flare.
• Use diameter inside bark when your market standard requires it.
• Measure length carefully and understand whether trim allowance is included.
• Record visible defects such as sweep, rot, shake, crook, and seams.
• Separate logs by species and likely grade instead of averaging a mixed pile.

Common sources of estimate error

1. Using outside-bark diameter when the rule expects inside-bark measurements.
2. Ignoring taper on long logs.
3. Counting unusable sections that will be trimmed out at the mill.
4. Applying the wrong log rule for the local buying region.
5. Assuming scaling volume equals saleable lumber output.

When Should You Use Each Method?

If you are dealing with a buyer, sawmill, timber sale, or state reporting form, use the rule that governs that market. If you are estimating rough output from a portable band mill for your own project, International 1/4-inch is often a practical benchmark because it behaves more consistently across a range of diameters. If you are in a hardwood market where Doyle is standard, however, using International may create unrealistic expectations during price discussions.

A cubic method is best used when your project is not based on traditional sawlog scaling. For example, cubic feet can be helpful when comparing biomass, shipping volume, carbon calculations, or rough wood utilization. But if your goal is to know how many board feet a mill buyer is likely to credit, use the relevant log rule instead.

Authoritative Forestry and Measurement References

For additional technical context, see these high-quality public resources:

• U.S. Forest Service for timber measurement, utilization, and forest products guidance.
• Penn State Extension for woodland management, board-foot concepts, and sawmill education.
• University of Minnesota Extension for educational material on wood measurement, forest products, and practical timber information.

Practical Example

Suppose you have five red oak logs, each 18 inches small-end diameter and 16 feet long. Using a board feet calculator:

• Doyle estimate per log: about 196 BF
• Scribner estimate per log: about 216 BF
• International 1/4 estimate per log: about 252 BF

Multiply by five logs and the total range becomes roughly 980 BF to 1,260 BF depending on the rule. That is a major spread, which is exactly why choosing the correct rule matters before negotiating a sale, buying logs, or planning production.

Bottom Line

A board feet calculator for logs is most valuable when it reflects the scaling rule used in your region or transaction. Diameter and length are only the beginning. The selected log rule can shift the estimate substantially, especially on small and mid-sized logs. For that reason, the smartest workflow is to measure carefully, choose the correct rule, compare values, and treat the final number as a realistic estimate rather than a guarantee of finished lumber output.

If you are managing woodland inventory, pricing veneer or sawlogs, or milling your own lumber, use the calculator above to compare methods instantly. The built-in chart makes it easy to see how Doyle, Scribner, International 1/4-inch, and a cubic conversion diverge for the same log dimensions, helping you make better forestry, purchasing, and milling decisions.

This calculator provides educational estimates only. Local log scaling rules, mill specifications, trim standards, bark deductions, and defect deductions may change final credited volume.