Board Feet From Log Calculator

Estimate the usable lumber yield from your logs using standard scaling rules.

Lumber Yield for Common Lengths (at current diameter)

Length (ft)	Doyle (BF)	Scribner (BF)	Int 1/4 (BF)

Table estimates based on a fixed small-end diameter.

What is a Board Feet from Log Calculator?

A board feet from log calculator is a specialized forestry tool used by sawmill operators, timber buyers, and woodworkers to estimate the volume of usable lumber contained within a raw log. Since logs are cylindrical and tapering, and sawmills lose material to sawdust (kerf) and bark, mathematical formulas known as “log rules” are required to predict actual yield.

Using a board feet from log calculator helps professionals determine the financial value of standing timber or felled logs. Whether you are selling timber from your land or buying logs for a custom furniture project, knowing the “board foot” (BF) volume is essential. A board foot is defined as a unit of volume equivalent to a board that is 12 inches wide, 12 inches long, and 1 inch thick (144 cubic inches).

Common misconceptions include the idea that every cubic inch of a log can be turned into lumber. In reality, factors like log taper, rot, and the thickness of the saw blade significantly reduce the final output, which is why different scaling rules like Doyle or International 1/4″ exist.

Board Feet from Log Calculator Formula and Mathematical Explanation

Calculating the volume of wood in a log involves several variables. The three most common formulas used in the United States and Canada are the Doyle Rule, the Scribner Rule, and the International 1/4-inch Rule.

The Doyle Log Rule

The Doyle rule is one of the oldest and most widely used in the Eastern US. It is known for underestimating small logs and overestimating large logs. The formula is:

BF = ((D – 4)² * L) / 16

The International 1/4-Inch Rule

This is considered the most accurate mathematical rule because it accounts for log taper and sawmill kerf (the 1/4-inch width of the saw blade). The formula for a 4-foot section is:

BF = (0.22 * D² – 0.71 * D) * (L / 4)

Variable Variables Table

Variable	Meaning	Unit	Typical Range
D	Small End Diameter (Inside Bark)	Inches	8″ – 40″
L	Log Length	Feet	8′ – 20′
BF	Board Feet (Volume)	Units	20 – 2,000+
Kerf	Saw Blade Thickness Loss	Inches	1/8″ – 1/4″

Practical Examples (Real-World Use Cases)

Example 1: The Hardwood Log. Imagine you have an Oak log with a small-end diameter of 16 inches and a length of 10 feet. Using the board feet from log calculator with the Doyle rule: ((16-4)² * 10) / 16 = (144 * 10) / 16 = 90 BF. If using the International 1/4″ rule, the result would be approximately 108 BF, reflecting a more realistic sawmill yield.

Example 2: Large Pine Log. A 24-inch diameter log that is 16 feet long. Doyle: ((24-4)² * 16) / 16 = 400 BF. Scribner: Approx 400 BF. International 1/4″: Approx 430 BF. On larger logs, the rules tend to converge more closely, though International still typically provides the highest estimate.

How to Use This Board Feet from Log Calculator

Follow these steps to get accurate results from our board feet from log calculator:

1. Measure the Diameter: Use a tape measure to find the diameter of the log at the small end. Measure inside the bark (from wood to wood). If the log is not perfectly round, take two measurements at 90 degrees and average them.
2. Measure the Length: Determine the total length of the log in feet. Most mills require a 3-4 inch “trim allowance” beyond the nominal length (e.g., a 12-foot log should actually be 12’4″).
3. Select Your Scaling Rule: Choose Doyle for most private sales in the East, Scribner for West Coast or US Forest Service standards, or International 1/4″ for the most accurate lumber estimate.
4. Analyze the Results: The board feet from log calculator will instantly display the predicted yield. Compare the different rules to see the range of potential lumber.

Key Factors That Affect Board Feet from Log Calculator Results

• Log Taper: Logs aren’t perfect cylinders. Higher taper rates mean more waste at the large end, which some rules handle better than others.
• Saw Kerf: The width of the saw blade removes wood as sawdust. The International 1/4″ rule assumes a 0.25-inch kerf, while modern thin-kerf bandsaws may yield more.
• Log Scaling Defects: Rot, cracks (checks), sweep (curvature), and knots can significantly reduce the actual board feet recovered compared to the theoretical board feet from log calculator output.
• Bark Thickness: Since diameter is measured inside the bark, failing to subtract bark thickness on a standing tree will lead to massive overestimations.
• Sawing Pattern: “Grade sawing” for high-quality boards vs. “live sawing” for speed changes the volumetric recovery efficiency.
• Market Standards: Local customs often dictate which rule is used. Using the wrong rule during a transaction could cost a buyer or seller thousands of dollars in “hidden” volume.

Frequently Asked Questions (FAQ)

Why does the Doyle rule give such low numbers for small logs?

The Doyle rule subtracts 4 inches for slab allowance before squaring the diameter. For an 8-inch log, this removes half the diameter, leading to a very high percentage of “waste” in the formula that doesn’t exist in reality.

Which rule is most beneficial for the buyer?

Buyers typically prefer the Doyle rule for smaller logs because it underestimates the volume, giving them a “buffer” for defects and processing costs.

What is a “Board Foot”?

A board foot is 1/12th of a cubic foot, or 144 cubic inches. It’s the standard unit of measurement for lumber in North America.

Can I use this for standing trees?

Yes, but you must estimate the diameter at the top of the first or second log, not just the DBH (diameter at breast height), and account for taper.

How does log length impact accuracy?

Longer logs (over 16 feet) have more taper. Most board feet from log calculator formulas work best when calculating logs in 8-foot to 16-foot segments.

What is “Scribner Decimal C”?

It is a variation of the Scribner rule that rounds the result to the nearest 10 board feet to simplify tallying in the field.

Does this calculator include sawdust waste?

Yes, all three rules (Doyle, Scribner, International) include built-in assumptions for “slabbing” and sawdust waste (kerf).

Why is my sawmill yield different from the calculator?

Thin-kerf bandsaws and skilled sawyers can often “overrun” the log scale, meaning they produce more lumber than the board feet from log calculator predicted.

Related Tools and Internal Resources

• Lumber Weight Calculator – Calculate the weight of specific wood species once sawn.
• Timber Yield Calculator – Estimate forest-wide wood production.
• Log Weight Calculator – Essential for transport and crane safety.
• Stumpage Value Calculator – Determine the financial value of standing timber.
• Cord of Wood Calculator – Best for firewood and pulpwood measurements.
• Board Foot Calculator – Calculate volume for finished dimensional lumber.