Calculate A Logs Board Feet

Estimate the board foot volume of one log or a full group of logs using common North American log rules. Enter the small-end diameter inside bark, merchantable log length, quantity, and preferred scale rule to calculate a fast, field-ready estimate.

How to calculate a log’s board feet accurately

Knowing how to calculate a log’s board feet is one of the most practical skills in forestry, portable sawmilling, timber buying, logging, firewood-to-sawlog sorting, and small woodland management. Board foot volume is the language many hardwood and softwood sawlog markets still use when estimating lumber yield. A board foot represents a piece of wood measuring 1 inch thick, 12 inches wide, and 12 inches long. In simple cubic terms, that equals 144 cubic inches. However, when people calculate board feet for logs, they usually are not measuring the exact cubic volume of the round log. Instead, they use a log scaling rule that estimates how many board feet of lumber may be sawn from that log.

This distinction matters. A round log contains bark, taper, defects, and slab loss when boards are sawn. Because of that, the board foot estimate from a scaling rule can be much lower than the log’s raw cubic wood volume. The rule you choose can significantly affect the final number, which is why the same log may produce different board foot estimates under the Doyle, Scribner, and International 1/4-inch rules. If you are selling timber, buying logs, comparing bids, or estimating sawmill output, understanding those differences helps you avoid confusion and price disputes.

Key idea: board foot calculations for logs are usually based on a scaling rule, not just geometry. That means your measurement method and your selected rule both influence the answer.

What measurements you need before using any board foot formula

Before you calculate anything, collect clean field measurements. The two core inputs are the small-end diameter and the merchantable log length. In most practical scaling systems, the small-end diameter is measured inside bark because bark does not become lumber. Depending on your region or buyer, the measurement may be rounded to the nearest whole inch, to even numbers, or according to local scaling conventions.

• Small-end diameter inside bark: Measured at the narrow end of the usable log, usually in inches.
• Log length: Merchantable or scaling length, usually in feet.
• Quantity: Useful when multiple logs are similar enough to group together.
• Scale rule: Doyle, Scribner, or International 1/4-inch are the most common choices in many U.S. markets.
• Defects and trim allowance: Rotten centers, sweep, crook, shake, and excessive taper may reduce actual yield from the theoretical rule estimate.

If you are measuring in the woods, keep a diameter tape, logger’s tape, and a notebook or mobile device handy. For repeatability, always note whether the bark is included, whether the length includes trim, and which rule your local sawmill uses. A precise measurement method is often more important than using a fancy calculator, because a one-inch difference in diameter can noticeably change the result.

The three major log rules and why they differ

The biggest source of variation in board foot estimates is the log rule itself. These rules were developed at different times and make different assumptions about slab thickness, kerf, taper, and sawing practice. As a result, they do not agree perfectly, especially for smaller logs.

1. Doyle Rule: Often used in hardwood regions. It tends to underestimate smaller logs and becomes more favorable as diameter increases.
2. Scribner Decimal C Rule: Based on diagrammed boards inside a log cross section. It is common in parts of the western and northern United States.
3. International 1/4-inch Rule: Designed to better account for taper and kerf. Many foresters consider it one of the most balanced rules across a wider range of sizes.

When someone says a log contains 200 board feet, the follow-up question should be, “By which rule?” Without that context, the number is incomplete. Two buyers quoting different prices per thousand board feet may actually be closer than they look once both are converted to the same scaling rule.

Rule	Typical use	Strength	Limitation	General market effect
Doyle	Common in many eastern hardwood markets	Simple and familiar to many buyers and sellers	Underestimates small logs significantly	Can make large logs look more favorable than small logs
Scribner Decimal C	Common in western and mixed regional markets	Widely recognized and easy to tabulate	Less consistent than International across some diameters and lengths	Often produces values between Doyle and International
International 1/4-inch	Forestry analysis, inventory work, many educational references	More realistic across wider size classes	Not the local buying rule everywhere	Often gives higher values for small and medium logs than Doyle

Board foot formulas used in this calculator

This calculator estimates board feet using commonly cited forms of the three major rules. The formulas are practical estimating tools, especially when you need a quick field value.

• Doyle: ((D – 4)² × L) / 16
• Scribner Decimal C estimate: (0.79 × D² – 2 × D – 4) × (L / 16)
• International 1/4-inch estimate: (0.905 × D² – 1.221 × D – 0.719) × (L / 4) / 4

In these formulas, D is the small-end diameter inside bark in inches and L is the log length in feet. Keep in mind that published tables and regional practices may round values in slightly different ways. In commercial scaling, official rule books, state extensions, or buyer-specific scales may control the exact method used in a transaction. Still, for planning, woodland inventory, and quick market comparisons, these formulas are highly useful.

Worked example: a 16-inch by 16-foot log

Suppose you have a log with a 16-inch small-end diameter inside bark and a merchantable length of 16 feet. The three rule estimates come out differently.

1. Doyle: ((16 – 4)² × 16) / 16 = 144 board feet
2. Scribner: (0.79 × 16² – 2 × 16 – 4) × (16 / 16) = about 166.24 board feet
3. International 1/4-inch: (0.905 × 16² – 1.221 × 16 – 0.719) × (16 / 4) / 4 = about 210.38 board feet

This example shows exactly why buyers, loggers, and landowners need to compare apples to apples. A price expressed in dollars per thousand board feet can look very different depending on the rule applied. If your market uses Doyle and a consulting forester reports timber volume in International 1/4-inch, direct conversion is necessary before comparing values.

Real-world comparison data for common log sizes

The table below shows estimated board foot volume for several common log sizes using the same formulas applied in this page calculator. These figures illustrate how the spread between rules is usually largest on smaller and mid-sized logs, then narrows somewhat as diameter increases.

Small-end diameter (in.)	Length (ft.)	Doyle BF	Scribner BF	International 1/4-inch BF	International vs Doyle difference
12	16	64	85.76	112.80	+76.3%
16	16	144	166.24	210.38	+46.1%
20	16	256	272.00	336.52	+31.5%
24	16	400	403.04	491.22	+22.8%

These statistics are not random examples. They reflect a consistent pattern that forestry professionals know well: the Doyle rule discounts smaller logs heavily. That is why small-diameter logs can seem surprisingly low when sold under Doyle compared with an International estimate. If you are planning a thinning, pre-harvest appraisal, or small sawmill run, understanding this spread can materially affect your budgeting.

How to use board foot estimates in forestry, milling, and timber sales

Once you know the board foot volume of a log or load, you can use that information in several practical ways. For woodland owners, board feet help estimate timber sale value. For portable sawmill operators, they help forecast output and compare actual recovery against theoretical scale. For log buyers, they simplify pricing and sorting by species, grade, and size class.

• Timber sale planning: Estimate gross volume before harvest and compare bids across buyers.
• Sawmill production: Forecast rough lumber output, slab waste, and drying loads.
• Inventory work: Build stand-level volume summaries for management plans.
• Load optimization: Group logs by diameter and length to match mill specifications.
• Value comparison: Separate high-grade butt logs from lower-grade upper stem sections.

However, board feet are not the full story. Lumber recovery depends on species, taper, sweep, crook, internal defects, sawing pattern, saw kerf, target dimensions, and operator skill. A straight, clear hardwood butt log may outperform its scale estimate in actual value because it yields higher grades. A knotty, crooked log with shake may produce less value than its board foot total suggests. Volume and value are related, but they are not identical.

Measurement best practices to improve accuracy

Good scaling starts with consistency. If your diameter measurements vary from person to person, your board foot estimate will also vary. The following best practices reduce error and make your numbers more credible in the field or in negotiations.

1. Measure the small end, not the large end, unless a local rule specifies otherwise.
2. Measure inside bark whenever possible because bark is not recoverable lumber.
3. Use a standard merchantable length and note trim separately.
4. Round measurements according to local market practice, not personal preference.
5. Record visible defects that may justify deductions.
6. Use the same log rule across all comparisons unless you deliberately convert between rules.

In formal timber cruising and scaling, foresters often rely on state extension publications, agency manuals, and region-specific scale tables. Those references help standardize methods across buyers and sellers. If you are working in a regulated sale environment, always defer to the documented contract scale rule and measurement protocol.

Common mistakes when calculating a log’s board feet

Even experienced landowners and mill operators make a few recurring errors. The most common mistake is using the diameter outside bark rather than inside bark. Another frequent problem is mixing rules without realizing it, such as comparing a Doyle price quote against an International estimate. People also sometimes confuse cubic feet, lineal feet, and board feet, which are completely different volume measures.

• Using bark-inclusive diameter
• Entering total tree height instead of log length
• Ignoring defects and taper
• Applying the wrong scale rule for the local market
• Assuming one board foot estimate equals actual sawn recovery
• Failing to round the way the buyer or scale manual requires

Another mistake is forgetting that small logs may be uneconomic under one rule but acceptable under another, especially in selective harvesting or custom milling. In regions where Doyle dominates, a small-diameter sawlog can seem to contain too little volume to justify hauling, while a more generous rule may support a different decision. That is why a calculator like this is most valuable when used as a comparison tool, not just a single-number answer generator.

Authority sources for log scaling and forest measurement

For deeper guidance, consult recognized public sources such as the U.S. Forest Service, the Penn State Extension, and the University of Minnesota Extension. These organizations publish timber measurement guides, forest inventory resources, log rule explanations, and practical woodland management references.

Final takeaway

To calculate a log’s board feet well, you need more than a single formula. You need the right log measurements, the right rule, and a clear understanding of what the number represents. Board feet are a standardized estimate of lumber output, not a perfect description of actual saw recovery. The Doyle, Scribner, and International 1/4-inch rules all have legitimate uses, but they produce different results, especially for smaller logs. If you measure carefully, use a consistent rule, and compare results with local buying practice, your estimates will be much more useful for timber sales, forest management, and milling decisions.

Educational use only. Final commercial scale values may differ based on local log rules, contract language, scaling deductions, trim practices, and buyer specifications.