Mastering the Doyle Rule for Estimating Lumber Volume: The Ultimate Guide to Accurate Log Scaling

In the timber industry, correct measurements are important when it comes to estimating the volume of lumber. Be it purchasing or selling timber, the method of measuring its volume may really impact on the value of the timber and process of logging itself. The Doyle Rule is one of the most popular techniques of scaling logs. We will dissect the Doyle Rule which is used to estimate the volume of lumber, discuss how it functions, contrast it with other popular rules of measuring logs such as the Scribner Rule and the International Rule, and offer tips on measuring the volume of lumber.

What is the Doyle Rule?

Doyle Rule is among the best-known log scaling techniques which have been used to estimate the board feet estimation of timber. It was invented by Edward Doyle in the mid-1800s and has been extensively utilized in particular in the eastern and southern regions of the United States. Board feet are standard unit of volume in the measurement of lumber volume which is a piece of wood 1 inch thick, 12 inches wide, and 12 inches long. The Doyle Rule is used to approximate the number of board feet that can be derived out of a log.

The Doyle Rule is simple enough to be described as follows:

Board Feet (Doyle Rule) = (D – 4)² x (L ÷ 16)

Where:

D = the diameter inside the bark at the small end of the log (in inches),
L is the log length (in feet),
The slab allowance (-4) is to counteract the loss of wood by the saw cutting process (a.k.a. kerf).

How Does the Doyle Rule Work?

The Doyle Rule makes the process of measuring logs easy by measuring the volume of the lumber in board feet. It operates using a formula that deduces a customary deduction of the outer part of the log that is not utilized because of the inefficiencies of the bark and sawmill. The key one here is a log taper which is the reduction of diameter of a log as you ascend the tree. Although the Doyle Rule does not directly take into consideration the taper of the log, the small diameter of the log is used as a reference point to determine the amount of usable wood that can be sawed out of that log.

Take the example of a log that has a diameter of 12 inches and a length of 16 feet as an example. The estimated value of board feet would be obtained using the formula above.

Example Calculation:

D = 12 inches, L = 16 feet

D – 4 = 12 – 4 = 8 inches
8² = 64
64 x (16 ÷ 16) = 64

It is calculated by the Doyle Rule that a log of 12 inches diameter, 16 feet long will give 64 board feet of lumber.

The Doyle Rule vs. Other Log Measurement Rules

Although the Doyle Rule has become an extensively utilized log scaling, it is not the only method of log scaling. The other common log rules that are used are the Scribner Rule and the International Rule. All of these rules possess their advantages and disadvantages; therefore, they are more suitable in different applications.

The Scribner Rule:

Scribner Rule is a diagram rule which was invented by J.M. Scribner in 1846. It approximates the board feet by the diagram and compensating the board length of various logs. Although the Scribner Rule is more precise in the case of longer logs that exceed 16 feet in length it is also characterized by erratic estimations, particularly in the cases of smaller diameter logs. This rule is based on the assumption that the taper of the log is very uniform, and this is not necessarily true.

The International Rule:

The International Rule was built in 1906 and takes into consideration more precisely the log taper than the Doyle Rule. It is regarded as one of the most accurate ways of determining the lumber volume measurement. The International Rule presupposes a taper of 1/2 inch to every 4 feet of length of log, and is consequently best suited to logs of great taper. It is commonly applied in timber sale to do a big timber estimation especially in a forest under the control of federal or state agencies.

Key Differences:

Scribner Rule is more suitable in long logs but can be inconsistent with small logs.
The most accurate estimates are given by International Rule but are not so popular because the rule is complicated.

Doyle Rule is easy to operate and is widely used and may under or overestimate the volume of timber especially the large logs.

When to Use the Doyle Rule

The Doyle Rule is quite effective in the cases where:

It needs simplicity: It is a simple equation that does not need any complex manipulations.
You are dealing with smaller logs: When the logs are not more than 28 inches in diameter, the Doyle Rule gives more valid estimates than any other rule.
Regional preference: The Doyle Rule is the timber valuation and log scaling standard that is used in most parts of the United States.

But when you are working with somewhat bigger logs, or with logs with significant taper, it might be more well to resort to the International Rule, or to the Scribner Rule, as the circumstances may warrant.

Advantages of the Doyle Rule

There are a number of benefits associated with the Doyle Rule:

Ease: The formula is not difficult to memorize and use.
Historical usage: It has been in operation since about 200 years and it still is a solid standard used in many areas.
Economical: The Doyle Rule gives swift and productive estimates without using sophisticated tools.

Weaknesses of the Doyle Rule

Although the Doyle Rule has its merits, it is also not without some flaws:

Underestimation of larger logs: The Doyle Rule is likely to under estimate larger logs (more so larger than 28 inches in diameter).
No allowance for log taper: The Doyle Rule does not directly involve the allowance of log taper, as with the International Rule, this may result in inaccurate estimates of tapered logs.
Irregularity in sawmill operations: Not all sawmills may be the same and therefore the volume estimation error caused by the Doyle Rule.

Practical Tips for Accurate Log Scaling

To obtain the best lumber volume measurement by using the Doyle Rule, here are some of the tips that can be put into practice:

Take the diameter of the log at the small end of the log, but be sure that you are within the bark. This is vital for an accurate estimation.
Inspect defects: Logs that are defected like those with rot, splits and extreme bends might not give as much usable lumber and the reader should therefore deduct when using the Doyle Rule.
Measure the correct length of the log: When taking measurements of logs, take into account that you have to measure the merchantable length of the log, that is, the length of the log between the stump and a point where the log is too small to be handled in the sawmill.
Take into consideration slab and kerf losses: As it was said above, the Doyle Rule already deduces a standard allowance of slab losses and kerf (the thickness of saw). Nevertheless, it is always better to remember about this when doing your calculations.

Frequently Asked Questions (FAQs)

Q1: What is the Doyle Rule for estimating lumber volume?

Answer: The Doyle Rule is a log scaling technique which is used to approximate the volume of usable lumber (in board feet) that a log would produce. This rule was developed by Edward Doyle in the 19^th century and is especially popular in hardwood species in the United States. The basic formula is:

Board Feet = ((Diameter – 4)² x Length) / 16

Where:

Diameter = Inside bark diameter at the small end of the log (in inches)
Length = Log length (in feet)

This equation is used to give an estimate which is on the lower side, in most cases, which underestimates the lumber yield of a log, particularly of a smaller log. (woodweb.com)

Q2: How do I use the Doyle Rule to estimate lumber volume?

Answer: To use the Doyle Rule:

Measure the diameter: Determine the Inside bark diameter of the log at the small end (in inches).
Length: Measure the length of the log (in feet).
Apply the Formula: Use the Formula above to calculate the board feet.

For example: For a 12 foot log having a diameter of 16 inches:

Board Feet = ((16 – 4)² x 12) / 16

= (12² x 12) / 16

= (144 x 12) / 16

= 1728 / 16

= 108 board feet

This is the rapid approximation but the real returns may vary. (woodweb.com)

Q3: What are the limitations of the Doyle Rule?

Answer: The Doyle Rule has limitations in a number of ways:

Underestimates Small Logs: The calculation removes 4 inches of the diameter then squares this number, and thus we can underestimate smaller logs.
No Taper Consideration: It has not taken into consideration the natural taper of logs and so it may not give realistic results.
Limited Slab and Edging Allowance: The rule permits a 4.5 percent deduction of sawdust and shrinkage, as compared to other policies that permit deductions of 10-30 percent. (gov)

Other methods such as the Scribner or International 1/4″ are apparently better suited in some conditions due to these situations.

Q4: How does the Doyle Rule compare to other log scaling methods?

Rule	Strengths	Weaknesses
Doyle	Simple, widely used, conservative	Underestimates small logs, no taper
Scribner	Accounts for saw kerf, widely used	No taper allowance, underestimates long logs
International	Accounts for taper, more accurate	Less commonly used, more complex

All of them have their pros and are selected depending on the needs and local preferences. (shelbycountytn.gov)

Q5: Where can I find a Doyle Log Scale chart?

Answer: Printable Doyle Log Scale Charts can be found online. These tables contain the computation of the estimated board feet of different diameters and lengths of logs. They are useful tools that help loggers, sawmill workers and buyers to determine the potential yield of a log within a short period of time.

For example, Global Timber Doyle Scale is a detailed scale that can be referred to.

Conclusion: Mastering the Doyle Rule for Estimating Lumber Volume

Doyle Rule remains a cornerstone in the rules of the log measurements and the rule assists the timber buyers, foresters, and landowners to measure the volume of the lumber at a very fast and effective rate. Despite the other rules, such as the Scribner Rule and International Rule, the Doyle Rule is a simple and efficient way out in most cases. Understanding its formula and when to use it, you can be sure of having the correct and practical estimates of timber sales and forest management.

For any timber deal or timber forest inventory, the Doyle rule can save time, money and confusions as far as you know how to apply it. Individuals who are landowners and want to sell timber, loggers who want to scale logs, and others who are interested in managing a forest stand better, mastering this rule is a valuable skill in the timber industry.

Additional Resources for Timber Measurement

Doyle Log Scale for further details on board foot estimation
Scribner Rule for comparative log measurement
International Rule for a more precise lumber volume method

Explore More Calculators

Looking for more handy tools? Try these other calculators from MegaToolCalculator.com:

Discover even more tools in our All Calculators section.