Log Volume Calculator

Log Volume & Board Foot Calculator

Estimated Yield

Doyle Scale 0 BF

Scribner Scale 0 BF

Intl 1/4″ Rule 0 BF

Cubic Volume 0 ft³

*BF = Board Feet. Results are estimates based on standard forestry formulas.

function calculateLogVolume() { var L = parseFloat(document.getElementById('logLength').value); var D = parseFloat(document.getElementById('smallDiameter').value); if (isNaN(L) || isNaN(D) || L <= 0 || D <= 0) { alert("Please enter valid positive numbers for length and diameter."); return; } // Doyle Rule: (D – 4)^2 * (L / 16) var doyle = Math.pow((D – 4), 2) * (L / 16); if (D <= 4) doyle = 0; // Scribner Decimal C (Simplified formulaic approximation) // (0.79*D^2 – 2*D – 4) * (L/16) var scribner = (0.79 * Math.pow(D, 2) – 2 * D – 4) * (L / 16); if (scribner < 0) scribner = 0; // International 1/4-Inch Rule // For 4-foot sections: (0.199*D^2 – 0.642*D) // We apply it linearly for simplicity, though real scaling involves taper. var intl = (0.22 * Math.pow(D, 2) – 0.71 * D) * (L / 4); if (intl < 0) intl = 0; // Cubic Volume (Huber's – using small end as proxy for average) // Area = PI * r^2. r in feet = (D/2)/12 var radiusInFeet = (D / 2) / 12; var cubicVolume = Math.PI * Math.pow(radiusInFeet, 2) * L; document.getElementById('doyleResult').innerHTML = Math.round(doyle); document.getElementById('scribnerResult').innerHTML = Math.round(scribner); document.getElementById('intlResult').innerHTML = Math.round(intl); document.getElementById('cubicResult').innerHTML = cubicVolume.toFixed(2); document.getElementById('logResultArea').style.display = 'block'; }

Understanding Log Volume Measurement

Calculating the volume of a log is essential for timber sales, sawmill management, and forest inventory. Unlike a perfect cylinder, trees are tapered and irregular, leading to the development of various "Log Rules" to estimate the usable lumber (board feet) that can be sawn from a log.

Common Log Scaling Rules

• Doyle Log Rule: One of the oldest rules, the Doyle scale is widely used in the Eastern and Southern US. It is known to significantly underestimate the volume of small logs while being relatively accurate for very large timber. This "under-run" often favors the sawmill operator.
• Scribner Log Rule: Developed in the mid-1800s, this rule is based on diagrams of 1-inch boards drawn within circles of various diameters. It does not account for log taper and is generally more accurate than Doyle, but still conservative compared to modern milling techniques.
• International 1/4-Inch Rule: This is scientifically the most accurate rule for predicting sawmill yield. It accounts for log taper and assumes a 1/4-inch "kerf" (the width of the saw blade cut). It is often used by foresters for inventory and research.
• Cubic Volume: This measures the total wood fiber content without considering the waste from sawing (slabs, sawdust, and edgings). It is the preferred unit for pulpwood, biomass, and international timber trade.

How to Measure a Log Correcty

To get the most accurate results from our calculator, follow these industry standards for measurement:

1. Measure the Length: Determine the length of the log in feet. Most mills buy in even increments (8′, 10′, 12′, 14′, 16′). Remember to allow for "trim" (usually 3-4 inches extra) so the mill can square the ends.
2. Measure the Diameter: Always measure the diameter at the small end of the log.
3. Inside the Bark: Measure the diameter "inside the bark" (DIB). Log rules are designed to calculate wood volume, not bark volume.
4. Average the Diameter: If the log end is oval-shaped, take two measurements (the narrowest and widest points) and use the average for your calculation.

Example Calculation

Suppose you have a White Oak log that is 16 feet long with a small-end diameter of 18 inches.

• Doyle: (18 – 4)² × (16 / 16) = 196 Board Feet
• International 1/4″: More complex math yields approximately 230 Board Feet
• Cubic Volume: Approximately 28.27 cubic feet of total wood

Notice the variation: the International Rule predicts about 17% more lumber than the Doyle rule for this specific log. This is why knowing which rule your buyer uses is critical for profit margins.