How Many Board Feet In A Log Calculator

Estimate lumber yield from a single log using common North American log rules. Enter the small-end diameter, usable log length, kerf allowance, and your preferred scale rule to calculate estimated board feet instantly and compare Doyle, Scribner, and International 1/4-inch outputs.

Log Board Foot Calculator

Estimate Notes

What this calculator does

• Estimates board feet based on standard log scaling rules.
• Shows the selected rule result and compares all three major rules.
• Accounts for optional bark deduction and trim allowance.
• Builds a chart so you can compare expected board foot output at a glance.

Expert Guide: How Many Board Feet Are in a Log?

A board foot is a unit of lumber volume equal to a board that is 12 inches long, 12 inches wide, and 1 inch thick. In practical forestry, sawmilling, and timber buying, people often need a faster way to estimate how many board feet a round log may produce before it is sawn. That is exactly where a how many board feet in a log calculator becomes useful. Instead of guessing from rough dimensions, the calculator applies a recognized log rule to estimate the lumber yield from a given diameter and length.

Although the concept sounds simple, log volume estimation is not perfectly straightforward. A round log is not a stack of boards. Saw kerf, slab loss, taper, defects, sweep, and trimming all reduce actual recoverable lumber. To standardize buying and selling, the forest products industry relies on scaling systems called log rules. In the United States, the most common are the Doyle rule, the Scribner rule, and the International 1/4-inch rule. Each one uses a different assumption about waste and sawing efficiency, which is why the same log can produce several different board foot estimates depending on the rule selected.

In most real-world transactions, the most important question is not just “what is the log volume?” but “which scale rule is the buyer and seller using?” Always confirm the rule before comparing prices, bids, or timber cruise estimates.

What Inputs Matter Most?

When using a board foot calculator for logs, the two primary measurements are diameter and length. Diameter is typically taken at the small end of the log. In many cases, scalers use the diameter inside bark, because bark does not turn into lumber. If you only have an outside-bark measurement, a bark deduction may be used to get a more realistic estimate. Length should reflect the merchantable sawlog length rather than an approximate total. If a log is 16 feet 6 inches but only 16 feet is merchantable after trim, your estimate should usually be based on 16 feet.

• Small-end diameter inside bark: Usually the most important dimension for scaling.
• Merchantable length: The usable log length that can actually be sawn.
• Scale rule: Doyle, Scribner, or International 1/4-inch.
• Bark deduction: Helps when only outside-bark diameter is available.
• Quantity of logs: Converts a single-log estimate into a tract, load, or inventory total.

Why Board Foot Estimates Change from Rule to Rule

The three major rules were developed in different periods and reflect different assumptions about saw kerf and milling practice. Older rules tend to underestimate small logs more severely. That is one reason a 12-inch log may show a large spread between Doyle and International, while a 28-inch log shows less dramatic percentage variation. The Doyle rule is widely known for being conservative on small diameters. Scribner tends to be somewhat more balanced, while International 1/4-inch is often viewed as more accurate across a broader range of diameters because it attempts to account more systematically for taper and sawing losses.

Log Rule	Typical Use	General Tendency	Best Known Characteristic
Doyle	Common in parts of the eastern and southern United States	Underestimates small logs	Simple and traditional, but harsh on smaller diameters
Scribner	Common in many regional markets and historical timber transactions	Moderate estimates	Based on diagrammed board layouts in a log cross-section
International 1/4-inch	Frequently used when a more consistent estimate is desired	Often higher than Doyle on small and medium logs	Attempts to reflect sawing losses more realistically

Common Approximate Formulas Used in Calculators

Many online calculators use simplified mathematical versions of traditional scale rules. These formulas are useful for field estimates and educational planning:

1. Doyle: Board feet = ((D – 4)² × L) ÷ 16, where D is diameter in inches and L is length in feet.
2. Scribner: Board feet = ((0.79 × D²) – (2 × D) – 4) × L ÷ 16.
3. International 1/4-inch: Board feet = ((0.199 × D²) – (0.642 × D) – 1) × L.

These formulas are convenient and widely used for estimation, but remember that official log scaling for a commercial sale may still follow local conventions, scaling sticks, mill rules, grade deductions, or state practices. A calculator should be treated as a planning tool unless it is explicitly matched to the buyer’s scaling standard.

How to Measure a Log Correctly

To get the most reliable answer from a calculator, careful measurement matters. First, clean enough bark and debris from the small end to see the true outline. Measure across the shortest diameter and, if needed, average that with the diameter at right angles to it. If the log is noticeably out of round, an average of two measurements gives a better estimate than relying on one. Next, determine usable length. Include only the straight, sound portion intended for sawing. Crook, rot, large knots near the butt, and trim loss can materially reduce recovery.

• Use a diameter tape, scale stick, or standard tape measure.
• Measure the small end, not the butt end, unless local practice specifies otherwise.
• If the bark is thick, use an appropriate bark deduction.
• Measure in whole feet or tenths of a foot, depending on your operation.
• Exclude obvious unusable trim unless your market buys by gross scale.

Worked Example

Suppose you have one log with a small-end diameter of 18 inches and a merchantable length of 16 feet. Using the simplified formulas in this calculator:

• Doyle: ((18 – 4)² × 16) ÷ 16 = 196 board feet
• Scribner: ((0.79 × 18²) – (2 × 18) – 4) × 16 ÷ 16 = about 216 board feet
• International 1/4-inch: ((0.199 × 18²) – (0.642 × 18) – 1) × 16 = about 827 board feet

This example illustrates an important point: formulas may represent scaling rules differently depending on the convention used by the calculator. The tool on this page is intended to provide a rule-based estimate, not a legal settlement measure. If you are selling timber, verify how your forester, consultant, or mill applies the rule in your region.

Comparison Statistics That Matter in Practice

Forestry extension publications and timber marketing guides repeatedly emphasize that differences in measurement method can strongly influence the apparent value of standing timber and delivered logs. That is why professional foresters urge landowners to understand units before agreeing to a sale. Even a modest difference in scale can compound into a significant change in total tract value when dozens or hundreds of logs are involved.

Metric or Statistic	Typical Industry Context	Why It Matters
1 board foot	12 in × 12 in × 1 in	Standard lumber volume unit used in sawtimber valuation
1 cubic foot	1,728 cubic inches	Useful for comparing solid wood volume to board foot estimates
1 thousand board feet (MBF)	1,000 board feet	Common commercial pricing unit for timber sales and log loads
Typical sawlog lengths	8 to 16 feet in many operations	Length choices affect scaling, trim loss, and merchandising options
Diameter sensitivity	Small logs show larger percentage differences among rules	Rule selection can materially change estimated value

Board Feet Versus Cubic Volume

Some users wonder why there is not a one-to-one conversion from cubic feet in a log to board feet of lumber. The reason is simple: board foot rules are not measuring pure wood volume alone. They are estimating usable sawn lumber output after accounting for processing loss. Two logs with the same cubic volume can produce different amounts of marketable lumber depending on taper, diameter, straightness, and defect. Larger-diameter logs generally produce more efficient lumber recovery because proportionally less material is lost to slabs and saw kerf.

When to Use This Calculator

• Estimating rough lumber yield from a single tree or small group of logs
• Preparing for a portable sawmill job
• Comparing likely outputs under different scaling rules
• Teaching forestry, wood science, or timber measurement concepts
• Planning a timber inventory or field estimate before a formal cruise

Limitations You Should Understand

No calculator can see internal defect, hidden rot, sweep, butt flare, metal contamination, severe taper, or the actual sawing pattern the mill will use. A veneer log, a high-grade hardwood butt log, and a knotty pulp-quality stem may all have very different real-world values even if they share the same diameter and length. Board foot calculators estimate quantity, not necessarily grade, price, or net profit. If you are dealing with a timber sale of meaningful value, a consulting forester is often the best investment you can make.

Likewise, regional timber markets often prefer a specific scale rule. A log that looks generous under International may not be purchased that way if local mills settle on Doyle. Always compare apples to apples by using the exact same rule and unit basis for all bids.

Best Practices for Landowners and Sawmill Users

1. Measure carefully and record species, diameter, and merchantable length.
2. Use the same rule consistently throughout your estimate.
3. Separate gross estimates from net estimates if defect is present.
4. Discuss the buyer’s scale rule before negotiating price per board foot.
5. For larger sales, seek advice from a qualified forester or extension specialist.

Authoritative Resources

For readers who want deeper technical guidance, these public sources are excellent starting points:

• U.S. Forest Service for timber measurement, forest products, and scaling references.
• Penn State Extension for practical guidance on board feet, timber sales, and forest landowner education.
• University of Minnesota Extension for woodland measurement and timber volume education.

Final Takeaway

A how many board feet in a log calculator is one of the quickest ways to turn field measurements into a usable sawtimber estimate. The key is understanding that the answer depends on the scale rule, measurement method, and log quality. If you measure the small-end diameter carefully, use a realistic merchantable length, and select the same rule used by your local market, you can get a practical estimate for planning, pricing, and comparing log yields. Use the calculator above to generate an instant estimate, compare rule outputs visually, and make more informed decisions about your timber or milling project.

Educational use note: calculator outputs are estimates based on common rule formulas and should not replace formal scaling procedures required in a commercial sale contract.