How To Calculate Board Footage In A Log (5 Pro Milling Tips)

How to Calculate Board Footage in a Log (5 Pro Milling Tips)

If you’re anything like me, the allure of transforming raw logs into usable lumber is irresistible. There’s a certain satisfaction in taking a tree from forest to finished product. However, before you fire up your chainsaw mill or call in the professionals, it’s crucial to understand how to accurately estimate the amount of lumber you can expect from a log. This is where calculating board footage comes in. It’s not just about guessing; it’s about making informed decisions, maximizing your yield, and avoiding costly surprises. I’ve spent years milling my own lumber, and I’ve learned a few tricks along the way to optimize board footage calculations. Let’s dive in!

The State of the Wood: Before we get started, consider that the global lumber market is a dynamic beast. In 2023, the market reached a value of US$631.8 Billion and is expected to reach US$791.2 Billion by 2032, exhibiting a growth rate (CAGR) of 2.5% during 2024-2032. Factors like housing starts, economic growth, and even global events can significantly impact lumber prices. Understanding board footage helps you make informed decisions about when to mill, what to mill, and how to price your lumber.

What is Board Footage?

Board footage is the standard unit of measurement for lumber volume. One board foot represents a piece of lumber that is 1 inch thick, 12 inches wide, and 12 inches long. Think of it as a cubic foot sliced into twelve thin boards.

Formula: (Thickness in inches) x (Width in inches) x (Length in feet) / 12 = Board Feet

Why is Calculating Board Footage Important?

Accurate Pricing: Knowing the board footage allows you to accurately price your lumber, whether you’re selling it or using it for your own projects.
Yield Estimation: It helps you estimate how much lumber you can realistically expect from a log, preventing disappointment and wasted effort.
Log Purchasing: When buying logs, understanding board footage enables you to assess the value of the log and negotiate a fair price.
Milling Efficiency: It allows you to optimize your milling process to maximize lumber yield and minimize waste.

Tip #1: Mastering the Doyle Log Scale – The Old Faithful

The Doyle Log Scale is one of the oldest and most widely used log scaling methods in North America, particularly in the eastern United States. While it tends to underestimate the actual board footage, especially in smaller logs, it’s still a valuable tool to understand, especially if you’re buying or selling logs in areas where it’s the standard. This is also important if you are purchasing a wood lot and the standing timber is being valued.

Formula: (Small End Diameter in inches – 4)^2 x (Length in feet) / 16 = Board Feet
- Small End Diameter: Measure the diameter of the log at the small end, inside the bark.
- Length: Measure the length of the log in feet.

Example:

Let’s say you have a log that is 12 feet long with a small end diameter of 16 inches.

(16 – 4)^2 x 12 / 16 = Board Feet

(12)^2 x 12 / 16 = Board Feet

144 x 12 / 16 = Board Feet

1728 / 16 = 108 Board Feet

According to the Doyle Log Scale, this log contains approximately 108 board feet.

Personal Story: I remember one time, I purchased a load of logs based on the Doyle scale. I felt like I got a great deal, but when I milled the logs, I was surprised at how much more lumber I actually got. This taught me the importance of knowing the limitations of the Doyle scale and understanding that it often underestimates the actual yield.

Why it Underestimates: The Doyle Scale was developed in the 19th century, and it doesn’t account for the taper of the log or the improvements in milling technology. It also assumes a certain amount of waste due to saw kerf (the width of the cut made by the saw).

Doyle Scale Limitations: This scale is known to significantly underestimate the yield, especially for smaller logs. It favors the buyer in log transactions.

Tip #2: Embracing the Scribner Log Scale – A More Realistic View

The Scribner Log Scale is another common log scaling method, known for providing a more accurate estimate of board footage compared to the Doyle scale, particularly for larger logs. It’s based on a diagram of boards that can be sawn from a log of a given diameter and length.

Scribner Log Scale Tables: The Scribner scale is typically used in the form of tables that provide board footage estimates based on log diameter and length. These tables are available online and in forestry handbooks.

How to Use Scribner Log Scale Tables:

Measure the Small End Diameter: Measure the diameter of the log at the small end, inside the bark.
Measure the Length: Measure the length of the log in feet.
Consult the Table: Find the corresponding board footage value in the Scribner Log Scale table based on the diameter and length measurements.

Example:

Let’s say you have a log that is 16 feet long with a small end diameter of 20 inches. Consulting a Scribner Log Scale table, you might find that a log with these dimensions yields approximately 220 board feet. (Consult a table for exact values).

Personal Story: I once used the Scribner scale to estimate the yield of a large oak log. The estimate was significantly higher than what the Doyle scale would have suggested. When I milled the log, the actual yield was very close to the Scribner estimate, proving its accuracy, especially for larger diameter logs.

Why it’s More Accurate: The Scribner scale is based on a more realistic assessment of the lumber that can be sawn from a log, taking into account factors like taper and saw kerf more effectively than the Doyle scale.

Scribner Scale Limitations: While more accurate than the Doyle scale, the Scribner scale can still underestimate the yield, particularly for logs with minimal taper or when using modern milling techniques that minimize waste.

Tip #3: The International 1/4-inch Log Scale – The Gold Standard for Accuracy

The International 1/4-inch Log Scale is considered the most accurate log scaling method, as it accounts for taper and saw kerf more precisely than other scales. It’s based on a mathematical formula that calculates the board footage assuming a 1/4-inch saw kerf. It is often used for timber cruises and appraisals.

Formula: (0.22D^2 – 0.71D) x L / 12 = Board Feet (per 4-foot section)
- D: Diameter inside bark at the small end of the 4-foot section in inches.
- L: Length of the log in feet.

How to Use the Formula:

Divide the Log into 4-Foot Sections: Divide the log into 4-foot sections.
Measure the Diameter: Measure the diameter inside bark at the small end of each 4-foot section.
Calculate Board Footage for Each Section: Use the formula to calculate the board footage for each 4-foot section.
Sum the Results: Add up the board footage values for all the sections to get the total board footage for the log.

Example:

Let’s say you have a log that is 12 feet long and you have divided it into three 4-foot sections. The diameters at the small ends of the sections are 18 inches, 17 inches, and 16 inches, respectively.

Section 1: (0.22 x 18^2 – 0.71 x 18) x 4 / 12 = (71.28 – 12.78) x 4 / 12 = 19.5 Board Feet
Section 2: (0.22 x 17^2 – 0.71 x 17) x 4 / 12 = (63.58 – 12.07) x 4 / 12 = 17.2 Board Feet
Section 3: (0.22 x 16^2 – 0.71 x 16) x 4 / 12 = (56.32 – 11.36) x 4 / 12 = 15 Board Feet

Total Board Footage = 19.5 + 17.2 + 15 = 51.7 Board Feet

According to the International 1/4-inch Log Scale, this log contains approximately 51.7 board feet. Note that the Doyle scale would have predicted 64 Board Feet based on the smallest diameter, a significant overestimate.

Personal Story: I once used the International 1/4-inch Log Scale to settle a dispute with a logging company. They were using the Doyle scale, which significantly underestimated the value of my logs. By using the International scale, I was able to prove that the logs contained much more lumber than they were claiming, resulting in a fairer price.

Why it’s the Most Accurate: The International 1/4-inch Log Scale is the most accurate because it considers the taper of the log and the saw kerf more precisely than other scales. It provides a more realistic estimate of the lumber that can be sawn from a log, especially when using modern milling techniques.

International 1/4-inch Log Scale Limitations: While the most accurate, the International 1/4-inch Log Scale can be more time-consuming to use, as it requires dividing the log into sections and performing calculations for each section.

Tip #4: Honing Your Visual Estimation Skills – The Intuitive Approach

While formulas and tables are valuable, developing your visual estimation skills is an invaluable asset. With experience, you can quickly assess a log and get a reasonable estimate of its board footage.

Practice, Practice, Practice: The more logs you see and mill, the better you’ll become at visually estimating their board footage.
Focus on Diameter and Length: Pay close attention to the diameter and length of the log, as these are the primary factors determining board footage.
Consider Taper: Account for the taper of the log, as this can significantly impact the yield.
Visualize the Boards: Try to visualize the boards that can be sawn from the log, considering the thickness and width of each board.
Compare to Known Logs: Compare the log to logs you’ve milled in the past, using those experiences as a reference point.

Personal Story: I remember when I first started milling, my visual estimates were way off. But after milling hundreds of logs, I developed a sense for how much lumber a log of a certain size would yield. Now, I can often get within 10% of the actual board footage just by looking at a log.

How to Improve Your Visual Estimation Skills:

Keep a Record: Keep a record of the logs you mill, noting the diameter, length, and actual board footage. Compare your visual estimates to the actual results to identify areas for improvement.
Attend Milling Demonstrations: Attend milling demonstrations and workshops to learn from experienced millers.
Consult with Experts: Talk to experienced loggers and millers to get their insights and tips.

Visual Estimation Limitations: Visual estimation is not as accurate as using formulas or tables, but it can be a useful tool for quick assessments and preliminary planning.

Tip #5: Leveraging Technology – Board Foot Calculators and Apps

In today’s digital age, technology can be a valuable ally in calculating board footage. Several online calculators and mobile apps can quickly and accurately estimate board footage based on log dimensions.

Online Calculators: Numerous websites offer free board foot calculators. Simply enter the log’s diameter and length, and the calculator will provide an estimate based on the chosen log scale. A simple search for “board foot calculator” will yield numerous results.
Mobile Apps: Several mobile apps are available for both iOS and Android devices that can calculate board footage. These apps often offer additional features, such as log scaling tools and timber cruising capabilities.
Software Programs: More advanced software programs are available for professional loggers and millers that can perform detailed log scaling and lumber yield analysis.

Personal Story: I used to rely solely on manual calculations, but once I discovered board foot calculators, it saved me a ton of time and effort. Now, I use a calculator to double-check my visual estimates and ensure accuracy.

Benefits of Using Technology:

Speed and Efficiency: Calculators and apps can quickly and accurately estimate board footage, saving time and effort.
Accuracy: Technology can eliminate human error and provide more accurate estimates.
Additional Features: Some apps and software programs offer additional features, such as log scaling tools, timber cruising capabilities, and lumber yield analysis.

Limitations of Using Technology:

Reliance on Input Data: The accuracy of the results depends on the accuracy of the input data. Be sure to measure the log dimensions carefully.
Dependence on Technology: Don’t become overly reliant on technology. It’s still important to understand the underlying principles of board footage calculation.

Bonus Tip: Understanding Log Defects and Their Impact on Board Footage

No log is perfect. Defects can significantly reduce the amount of usable lumber you can obtain. Understanding common log defects and how to account for them is crucial for accurate board footage estimation.

Knots: Knots are the most common log defect. They occur where branches grew from the tree. Knots can reduce the strength and appearance of lumber.
Rot: Rot is caused by fungal decay. It can weaken the wood and make it unusable.
Checks and Splits: Checks and splits are cracks in the wood. They can be caused by drying or stress.
Shake: Shake is a separation of the wood along the growth rings.
Sweep and Crook: Sweep and crook are bends in the log. They can make it difficult to saw straight boards.

How to Account for Log Defects:

Visual Inspection: Carefully inspect the log for any signs of defects.
Deduction: Deduct the estimated volume of the defect from the total board footage estimate.
Experience: With experience, you’ll become better at estimating the impact of defects on board footage.

Personal Story: I once milled a beautiful-looking cherry log, only to discover that it had extensive rot hidden inside. I ended up getting far less usable lumber than I had anticipated. This taught me the importance of carefully inspecting logs for defects, even if they look good on the surface.

Chainsaws and Milling: A Quick Note on Tool Selection

The right tools can make all the difference in maximizing your lumber yield.

Chainsaw Power: A more powerful chainsaw will handle larger logs more efficiently. Look for a chainsaw with at least 70cc engine displacement for milling. I personally have great success with saws over 90cc for larger logs.
Bar Length: Choose a bar length that is at least 2 inches longer than the diameter of the largest log you plan to mill.
Milling Chain: Use a specialized milling chain that is designed for ripping lumber. These chains have a different tooth geometry than standard chains, resulting in smoother and more efficient cuts.
Chainsaw Mill Attachment: Invest in a quality chainsaw mill attachment that is designed for accurate and stable milling.

Chainsaws are great for portability but can be slower than other methods. Axes, while traditional, are generally not suitable for producing lumber, but excellent for splitting firewood.

Drying and Seasoning: The Final Step

Once you’ve milled your lumber, it’s crucial to dry and season it properly. Green wood contains a high moisture content, which can cause it to warp, crack, and shrink as it dries. Proper drying and seasoning will ensure that your lumber is stable and ready for use.

Air Drying: Air drying is the most common method of drying lumber. It involves stacking the lumber in a well-ventilated area and allowing it to dry naturally over time.
Kiln Drying: Kiln drying is a more rapid method of drying lumber. It involves placing the lumber in a kiln and controlling the temperature and humidity to accelerate the drying process.

Moisture Content Targets:

Furniture and Cabinetry: 6-8% moisture content
Interior Trim: 8-10% moisture content
Exterior Construction: 12-15% moisture content

Statistics on Drying: Air drying typically takes several months to a year, depending on the species of wood and the climate. Kiln drying can be completed in a matter of days or weeks. Studies show that properly dried lumber is significantly more stable and less prone to warping and cracking.

Firewood Preparation: A Complementary Skill

While this guide focuses on lumber, many of the skills and tools used for milling are also applicable to firewood preparation. Understanding wood species, splitting techniques, and drying methods are essential for both.

Wood Species: Different wood species have different burning properties. Hardwoods like oak, maple, and ash burn hotter and longer than softwoods like pine and fir.
Splitting Techniques: Proper splitting techniques can make the job easier and safer. Use a sharp axe or a hydraulic log splitter.
Drying Methods: Firewood needs to be dried properly to burn efficiently. Stack the wood in a well-ventilated area and allow it to dry for at least six months.

Personal Story: I often use the smaller pieces of wood that are unsuitable for lumber to make firewood. It’s a great way to utilize all of the wood from a tree and reduce waste.

Firewood Stacking Case Study: A study conducted by the University of Maine found that stacking firewood in single rows, with good air circulation, resulted in significantly faster drying times compared to traditional, tightly packed stacks.

Cost and Budgeting Considerations

Calculating board footage is just one piece of the puzzle. You also need to consider the costs associated with milling your own lumber.

Equipment Costs: Chainsaws, chainsaw mills, safety gear, drying equipment.
Log Costs: Purchasing logs or harvesting your own trees.
Labor Costs: Your time and effort.
Maintenance Costs: Chainsaw maintenance, fuel, oil, and repairs.

Resource Management Tips:

Utilize All of the Wood: Use the smaller pieces for firewood or other projects.
Minimize Waste: Optimize your milling process to reduce waste.
Source Logs Locally: Reduce transportation costs by sourcing logs locally.
Barter and Trade: Trade lumber or firewood for other services or materials.

Troubleshooting and Common Pitfalls

Milling your own lumber can be challenging. Here are some common pitfalls to avoid:

Inaccurate Measurements: Ensure that you are measuring the log dimensions accurately.
Ignoring Log Defects: Carefully inspect logs for defects and account for them in your board footage estimates.
Improper Drying: Dry lumber properly to prevent warping, cracking, and shrinking.
Dull Chainsaw: Keep your chainsaw sharp to ensure smooth and efficient cuts.
Safety Hazards: Always wear appropriate safety gear and follow safe milling practices.

Next Steps and Additional Resources

Now that you have a solid understanding of how to calculate board footage, it’s time to put your knowledge into practice. Here are some next steps and additional resources to help you on your journey:

Practice: Start by milling a few small logs to gain experience.
Join a Local Woodworking Club: Connect with other woodworkers and learn from their experiences.
Attend Milling Workshops: Attend milling workshops to learn from experienced millers.
Consult with Experts: Talk to experienced loggers and millers to get their insights and tips.
Suppliers of Logging Tools: Baileys, Northern Tool, Forestry Suppliers.
Drying Equipment Rental Services: Check with local rental companies or woodworking supply stores.

Conclusion: From Log to Lumber, A Rewarding Journey

Calculating board footage is an essential skill for anyone involved in wood processing, logging, or firewood preparation. By mastering the techniques outlined in this guide, you can accurately estimate lumber yields, optimize your milling process, and make informed decisions about log purchasing and pricing. Remember, it’s a journey of continuous learning and improvement. The more you practice and experiment, the better you’ll become at transforming raw logs into beautiful and functional lumber. So, grab your chainsaw, sharpen your skills, and embark on the rewarding journey from log to lumber! It’s a labor of love, but as I often say, “A tree falls in the forest, and I’m going to turn it into something beautiful!”

How to Calculate Board Footage in a Log (5 Pro Milling Tips)