Calculate Board Feet In A Log Table

Estimate gross and net board feet from small-end diameter, log length, quantity, and log rule. This calculator compares Doyle, Scribner, and International 1/4-inch rule outputs so you can evaluate timber volume with confidence.

Log Board Foot Calculator

Formula note: this estimator uses standard board foot log rule equations commonly applied in field scaling. For exact sale or mill settlement, local rules, trim allowances, defect interpretation, and species practice may change the final tally.

Expert Guide: How to Calculate Board Feet in a Log Table

Calculating board feet in a log table is one of the most practical skills in forestry, sawmilling, hardwood buying, and timber appraisal. If you work with standing timber, delivered logs, or sawn lumber planning, you need a reliable way to estimate how much usable wood a log can produce. That estimate is usually expressed in board feet, a standard unit for lumber volume. A single board foot equals a board that is 1 inch thick, 12 inches wide, and 12 inches long. In pure geometric terms, that is 144 cubic inches, or 1/12 of a cubic foot before surfacing and drying adjustments are considered.

When someone says they want to calculate board feet in a log table, they usually mean they want to use a log rule or log scale table to convert log diameter and log length into a board foot estimate. This is not the same thing as calculating the cubic volume of a cylinder. Log rules estimate likely lumber yield after accounting for slabs, saw kerf, taper, and practical sawing losses. Because those assumptions differ, the result can change significantly depending on whether you use the Doyle rule, the Scribner rule, or the International 1/4-inch rule.

Key idea: a log table is an estimating tool, not a universal truth. The same 16-foot log can produce very different board foot values under different rules, especially at small diameters.

What information you need before using a log table

To estimate board feet accurately, gather the same field measurements a scaler or buyer would review:

• Small-end diameter inside bark: Most log rules use the diameter at the small end, not the butt end. Bark thickness is excluded for consistency.
• Log length: Common merchantable lengths include 8, 10, 12, 14, 16, 18, and 20 feet, but your market may use trim allowances.
• Log rule: Decide whether the table is based on Doyle, Scribner, or International 1/4-inch.
• Defect deduction: Rot, sweep, shake, crook, or mechanical damage can reduce merchantable yield.
• Log count: A truckload, landing pile, or timber sale estimate often includes multiple logs.

Most disputes in log scaling happen because one of those inputs was measured differently, not because the math itself is difficult. If diameter is taken over bark instead of inside bark, or if trim is ignored, the estimate can shift enough to matter financially.

Understanding the main log scaling rules

In North America, three log rules dominate practical board foot estimation. Each one reflects a different historical assumption about saw kerf and recovery. That means each rule has a built-in bias. Learning these differences is essential if you want to read a log table correctly.

Doyle Rule

The Doyle rule is widely known and still used in some hardwood markets. It is easy to compute, but it tends to underestimate small logs because it assumes a large slab and waste allowance. For a single log, the common formula is:

Doyle board feet = ((D – 4)² × L) / 16

Where D is small-end diameter inside bark in inches and L is log length in feet. The rule becomes more favorable as diameter increases, which is why buyers and sellers should always know which scale is being used.

Scribner Rule

The Scribner rule was developed from a diagrammed sawing pattern. It is often viewed as more moderate than Doyle, especially for medium diameters. A common decimal approximation is:

Scribner board feet = (0.79 × D² – 2 × D – 4) × (L / 16)

This rule still has limitations, but it generally tracks yield more evenly than Doyle for many practical sawlog sizes.

International 1/4-inch Rule

The International 1/4-inch rule is often considered the most technically balanced of the three because it attempts to account for taper and a more realistic saw kerf. A useful approximation is:

International board feet = (0.22 × D² – 0.71 × D) × (L / 4)

Foresters often prefer this rule when a more consistent estimate across diameter classes is needed. In many comparisons, it produces higher values than Doyle and somewhat higher values than Scribner, particularly in smaller and medium-size logs.

Step-by-step method to calculate board feet in a log table

1. Measure the small-end diameter inside bark. If your diameter tape gives outside bark diameter, subtract bark thickness according to local practice.
2. Measure merchantable length. Use the actual log length or the scaling length required by the mill or sale contract.
3. Select the correct log rule. Using the wrong table can distort value comparisons immediately.
4. Find the row for diameter and the column for log length. Traditional log tables list board feet at the intersection.
5. Apply any defect deduction. If a log has 10 percent defect, multiply the gross board feet by 0.90 to estimate net board feet.
6. Multiply by the number of logs. This gives total gross and total net volume for a group.

That is exactly what the calculator above automates. You enter the measurements, choose the rule, and it performs the same process instantly while also comparing the result against the other common rules.

Worked example: 16-inch by 16-foot log

Suppose you have one sound log with a small-end diameter inside bark of 16 inches and a merchantable length of 16 feet. Here is how the three rules compare using standard formulas.

Log Size	Doyle Rule	Scribner Rule	International 1/4-inch Rule	Difference from Doyle
12 in x 16 ft	64 bf	85.8 bf	92.6 bf	+34 percent to +45 percent
16 in x 16 ft	144 bf	166.2 bf	179.8 bf	+15 percent to +25 percent
20 in x 16 ft	256 bf	272.0 bf	295.2 bf	+6 percent to +15 percent

These figures illustrate a real and important trend: the smaller the log, the larger the relative gap between log rules. This is one reason timber buyers, private landowners, and consulting foresters must specify the scaling rule before discussing price per thousand board feet.

How a log table differs from cubic volume

A common beginner mistake is to treat a log like a perfect cylinder, compute cubic feet, and then divide by 1/12 to estimate board feet. While that may provide a rough physical volume, it does not reflect sawmill recovery. Logs taper, bark consumes space, slabs are removed to square the cant, and saw kerf turns wood into sawdust. Log tables are specifically designed to estimate recoverable lumber volume, not just wood mass.

That distinction matters in sales, procurement, and inventory analysis. A logger paid in tons, a forester cruising in board feet, and a mill tracking recovery in lumber tally may all look at the same piece of wood through different measurement systems. Board foot log tables remain popular because they connect forest inventory with practical lumber output.

Comparison table: gross vs net board feet after defect deduction

Defect deductions can substantially change the usable tally. The following examples use a 16-inch by 16-foot log under the International 1/4-inch rule.

Gross Volume	Defect Deduction	Net Factor	Net Board Feet	Use Case
179.8 bf	0 percent	1.00	179.8 bf	Sound, straight sawlog
179.8 bf	10 percent	0.90	161.8 bf	Minor sweep or limited defect
179.8 bf	20 percent	0.80	143.8 bf	Visible defect affecting recovery
179.8 bf	30 percent	0.70	125.9 bf	Heavy defect or downgraded log

Best practices for field accuracy

• Measure diameter at the correct end. Most rules rely on small-end diameter inside bark. Measuring the larger butt end inflates scale.
• Use consistent length conventions. Some mills buy on exact length, while others use nominal lengths with trim allowances.
• Separate species and grades. Board feet measure volume, not value. Species and grade can influence price far more than a small change in scale.
• Record defect honestly. Gross scale is useful, but net scale is often what matters commercially.
• Know the local market standard. A fair number under one rule may be viewed as high or low under another.

Why buyers and landowners should care about the chosen log rule

Imagine two offers on the same truckload of logs. One buyer quotes a stronger price per thousand board feet but uses Doyle. Another quotes a lower price per thousand but uses International 1/4-inch. Without converting the estimate to a common basis, you cannot compare bids fairly. This is a classic source of confusion in timber sales. Transparent volume estimates protect both parties and make appraisal work more defensible.

Consulting foresters often normalize bids to a common rule or supplement the estimate with weight, cubic volume, or mill studies. That kind of cross-check is especially useful in mixed hardwood sales where diameter distribution can strongly affect how each log rule behaves.

Common mistakes when using a board foot log table

1. Using outside-bark diameter without adjustment.
2. Mixing decimal and nominal lengths incorrectly.
3. Applying the wrong regional log rule.
4. Ignoring defect deductions in sale valuation.
5. Comparing price quotes without matching the scaling basis.
6. Assuming board feet equal final kiln-dried lumber tally.

When to use a calculator instead of a printed log table

Printed tables are still valuable in the woods because they are quick, durable, and easy to reference when cell service is weak. However, a digital calculator offers several advantages. It can calculate multiple rules instantly, handle defect deductions automatically, total groups of logs, and visualize how estimates change under different assumptions. That makes it ideal for landowner education, mill yard comparisons, and pre-sale planning.

The calculator on this page is especially useful if you want to understand how sensitive board foot volume is to diameter, length, and scaling rule. Enter the same dimensions and switch from Doyle to Scribner or International to see how much the output changes. That side-by-side perspective often teaches more than a static log table can.

Authoritative references for log scaling and timber measurement

If you want deeper technical guidance, review materials from established forestry and extension sources. The following references are helpful for measurement methods, timber cruising, and forest products education:

USDA Forest Service Penn State Extension University of Missouri Extension

Final takeaway

To calculate board feet in a log table, you need the small-end diameter inside bark, the merchantable log length, and the correct log rule. From there, the table or formula gives a gross board foot estimate, and any defect deduction leads to a net figure. The most important practical lesson is that the chosen rule matters. Doyle, Scribner, and International 1/4-inch can produce noticeably different estimates for the same log, especially in smaller diameters.

If you want a fast, transparent estimate, use the calculator above. It converts field measurements into board feet, applies defect deduction, totals multiple logs, and visualizes rule-by-rule differences in one step. That makes it a practical tool for landowners, foresters, buyers, and sawyers who need a clear, consistent estimate before logs are sold or sawn.