Board Feet In A Tree Calculator

Estimate the potential lumber yield from a log before milling.

Estimated Yield

256 BF

Inputs: 20″ Diameter, 16′ Length, Doyle Rule

What is a Board Feet in a Tree Calculator?

A board feet in a tree calculator is a specialized tool used in forestry and woodworking to estimate the volume of usable lumber in a log. A “board foot” (BF) is the standard unit of volume for lumber, representing a piece of wood that is 12 inches long, 12 inches wide, and 1 inch thick, or 144 cubic inches. This calculator does not measure the total wood volume of a tree, but rather the *potential yield* of milled boards after accounting for material lost to sawdust, slabs, and edgings.

This tool is essential for landowners, foresters, sawmill operators, and woodworkers. It helps in assessing the value of standing timber, planning milling operations, and purchasing logs. Common misunderstandings arise from confusing total tree volume with actual lumber yield; this calculator uses established “log rules” or formulas to provide a realistic estimate of the latter. For more information on volume, see our lumber volume calculator.

Board Feet Formula and Explanation

There isn’t one single formula, but three primary log rules used in North America. Our board feet in a tree calculator allows you to choose between them, as each gives a different result.

1. Doyle Log Rule

One of the oldest and most common rules, particularly in the eastern and southern United States. It is known for underestimating the yield of small logs and overestimating large ones.

Formula: BF = ((D - 4)²) * L / 16

2. Scribner Log Rule

This rule was created by drawing diagrams of the board ends that could be sawn from different diameter logs. It is generally considered more accurate than Doyle but doesn’t account for log taper.

Formula: BF = (0.79 * D² - 2*D - 4) * L / 16

3. International 1/4-Inch Rule

This is the most mathematically consistent rule and is considered the most accurate, as it accounts for a standard log taper of 1/2 inch every 4 feet and a 1/4-inch saw kerf. It often predicts the actual lumber yield most closely.

Formula: It is calculated in 4-foot sections. A simplified version is: BF_4ft_section = (0.905 * (0.22 * D² - 0.71 * D)). The total is the sum of all sections.

Formula Variables

Variable	Meaning	Unit	Typical Range
BF	Board Feet	(Unitless Volume Measure)	5 – 5000+
D	Log Diameter (small end, inside bark)	Inches	8 – 60+
L	Log Length	Feet	8 – 24+

Practical Examples

Example 1: Standard Hardwood Sawlog

• Inputs: Diameter = 24 inches, Length = 12 feet
• Doyle Rule Result: ((24 – 4)²) * 12 / 16 = (20²) * 0.75 = 400 * 0.75 = 300 BF
• Scribner Rule Result: (0.79 * 24² – 2*24 – 4) * 12 / 16 = (455.04 – 48 – 4) * 0.75 = 403.04 * 0.75 ≈ 302 BF
• International 1/4-Inch Rule Result: Approximately 320 BF

This example shows how for a medium-sized log, the Scribner and Doyle rules give similar results, while the International rule often suggests a slightly higher yield. For help with scaling, check our guide on the Doyle log rule.

Example 2: Small Pine Log

• Inputs: Diameter = 10 inches, Length = 16 feet
• Doyle Rule Result: ((10 – 4)²) * 16 / 16 = 6² * 1 = 36 BF
• Scribner Rule Result: (0.79 * 10² – 2*10 – 4) * 16 / 16 = (79 – 20 – 4) * 1 = 55 BF
• International 1/4-Inch Rule Result: Approximately 65 BF

This clearly illustrates the Doyle rule’s tendency to significantly underestimate the volume of smaller logs compared to the other rules.

How to Use This Board Feet in a Tree Calculator

Using our tool is straightforward. Follow these steps for an accurate estimate:

1. Measure Diameter: Measure the diameter of the log at its smallest end, *inside* the bark. If the log is not perfectly round, take two measurements at 90 degrees to each other and average them. Enter this value in the “Log Diameter” field in inches.
2. Measure Length: Measure the usable length of the log. This should not include major defects or forks. Enter this value in the “Log Length” field in feet.
3. Select a Log Rule: Choose the appropriate log rule from the dropdown menu. If you are selling timber, the buyer often dictates the rule. For personal estimation, the International 1/4-Inch rule is generally the most accurate. Our Scribner vs Doyle comparison guide can help you decide.
4. Interpret Results: The calculator will instantly display the estimated board feet. The primary result is shown prominently, and the chart below provides a comparison with the other two rules, giving you a comprehensive view of the potential yield.

Key Factors That Affect Board Feet Yield

The estimate from any board feet in a tree calculator is affected by real-world conditions. Here are six key factors:

• Taper: Trees are wider at the base than at the top. Rules like Doyle and Scribner do not account for this taper, while the International rule does, which is one reason it’s more accurate.
• Defects: Rot, knots, cracks, and sweep (curvature) in a log reduce the amount of clear, usable lumber and are not accounted for in the basic formulas. The scaler must manually deduct volume for these defects.
• Saw Kerf: This is the thickness of the saw blade. A thicker blade turns more wood into sawdust, reducing yield. The International 1/4-Inch rule explicitly accounts for a 1/4″ kerf.
• Sawyer Skill: An experienced sawyer can orient and cut a log to maximize the yield of high-quality boards, significantly impacting the final board footage.
• Measurement Accuracy: Small errors in measuring diameter or length can lead to significant differences in the calculated volume, especially with the Doyle rule.
• Log Length: Longer logs have more taper. Rules that ignore taper become increasingly inaccurate as log length increases. Learn more with our how to measure board feet guide.

FAQ about the Board Feet Calculator

1. What is the most accurate log rule?
The International 1/4-Inch rule is widely considered the most accurate because it mathematically accounts for log taper and saw kerf, two major factors in lumber yield.

2. Why do people still use the Doyle rule if it’s inaccurate?
Tradition is a major reason. It’s simple to calculate and has been used for centuries. In many regions, log buyers and sellers are accustomed to its values, and pricing is adjusted accordingly. It often favors the buyer on small logs, which require more handling per board foot.

3. Can I use this calculator for a standing tree?
Yes, but with estimations. You would measure the diameter at breast height (DBH, 4.5 feet from the ground) and estimate the usable, or merchantable, height of the trunk. This provides a rough estimate of the potential logs within the tree. A tree value calculator can provide further insights.

4. What does ‘inside bark’ mean for the diameter?
Lumber is made from the wood, not the bark. You must measure the diameter of the wood itself, excluding the bark’s thickness. If you measure outside the bark, your estimate will be too high.

5. How does log straightness affect board feet?
A curved log (sweep) will yield significantly less lumber than a straight one. The sawyer must cut along straight planes, meaning a lot of wood is wasted to get straight boards from a curved log. The formulas assume a perfectly straight log.

6. Why are my results different from another calculator?
Ensure you are using the same log rule, diameter, and length. Some calculators may use slightly different mathematical approximations for the Scribner rule, which was originally based on diagrams, not a strict formula.

7. Does tree species affect the board foot calculation?
The formulas themselves do not change based on species. However, different species have different growth habits (like taper and defect frequency) which will affect the *actual* final yield compared to the calculated estimate.

8. What’s the difference between a board foot and a linear foot?
A board foot is a measure of volume (Length x Width x Thickness). A linear foot is simply a measure of length. Lumber is often priced by the board foot, so knowing the volume is crucial for estimating cost.