Board Feet in a Log Calculator
Estimate board feet from a single log using gross cylindrical volume or common log rules such as Doyle, Scribner, and International 1/4-inch. Enter your measurements, compare methods instantly, and visualize the result on a chart.
Tip: If you do not know the large-end diameter, leave the default or enter the same value as the small end for a straight log. Gross board feet is a geometric estimate, while log rules estimate sawmill yield.
Results
Enter your log measurements and click Calculate Board Feet.
Expert Guide to Calculating Board Feet in a Log
Calculating board feet in a log is one of the most practical skills in forestry, sawmilling, woodlot management, and timber buying. Whether you are pricing sawlogs, comparing a portable mill job, valuing standing timber, or simply trying to understand how much lumber a felled tree might produce, the board foot is the traditional unit that connects raw logs to lumber output. A board foot represents a volume of wood equal to 12 inches by 12 inches by 1 inch, or 144 cubic inches. In cubic terms, one board foot equals one-twelfth of a cubic foot.
At first glance, the idea sounds simple: measure the log, calculate volume, and convert that volume to board feet. In practice, however, the answer depends on what you are trying to estimate. If you want the geometric wood volume of a round log, you can calculate a gross board foot equivalent from the log’s diameter and length. If you want a traditional estimate of sawn lumber yield, you usually apply a log rule such as Doyle, Scribner, or International 1/4-inch. These rules were developed to account for slab loss, saw kerf, taper, and the practical realities of turning a round log into rectangular boards.
What a board foot actually measures
A board foot is a unit of volume, not just area. The standard definition is:
- 12 inches wide
- 12 inches long
- 1 inch thick
That equals 144 cubic inches. Because there are 1,728 cubic inches in a cubic foot, one board foot is exactly 1/12 of a cubic foot. This relationship matters because it lets you move between geometric log volume and estimated lumber volume. If you know a log’s cubic feet, multiplying by 12 gives a gross board foot equivalent. That is useful for understanding the total wood in the stem, but it is not the same thing as merchantable lumber yield.
The difference between gross volume and log scale
When people say they are “calculating board feet in a log,” they may mean one of two things:
- Gross board foot equivalent: the log is treated as a cylinder or tapered solid, and volume is converted directly into board feet.
- Scaled board feet: a log rule estimates how many board feet of lumber the log is expected to produce in milling.
Both methods are valid, but they answer different questions. Gross volume tells you how much wood exists physically in the log. A log rule tells you how much board-foot lumber you may recover after accounting for waste. Because waste is unavoidable, scaled board feet are often lower than gross geometric board feet.
The measurements you need
To calculate board feet in a log correctly, you need a few basic inputs:
- Small-end diameter: the diameter at the small end of the log, usually measured inside bark for accurate scaling.
- Large-end diameter: useful for gross volume estimates when the log has noticeable taper.
- Log length: commonly measured in feet, often in 8, 10, 12, 14, 16, or 20-foot increments depending on the market.
- Bark condition: inside-bark measurements are preferred for estimating net wood volume.
- Scaling rule: Doyle, Scribner, or International 1/4-inch depending on region and sale terms.
Good measurements are the foundation of a good estimate. Diameter errors of only an inch or two can create large board-foot differences, especially on higher-value logs. Measure diameter at the correct end, keep your tape level, and note whether you are measuring inside or outside bark.
How gross board feet is calculated
The simplest geometric method treats the log like a cylinder. If a log has little taper, this is a quick and useful estimate. The process is:
- Convert diameter from inches to feet.
- Find the radius in feet.
- Calculate cross-sectional area using pi times radius squared.
- Multiply by length to get cubic feet.
- Multiply cubic feet by 12 to get gross board feet equivalent.
For a tapered log, a practical shortcut is to average the small-end and large-end diameters before doing the cylinder calculation. This is still a geometric estimate, not a formal log rule, but it better reflects the actual wood volume of a tapered stem. Portable sawyers and woodland owners often use this method to get a quick sense of material before deciding whether a log is worth milling.
Understanding the major log rules
Traditional log rules were designed to estimate lumber recovery from round logs. They differ because they make different assumptions about slab loss, taper, and saw kerf.
- Doyle rule: common in parts of the eastern and central United States. It tends to under-scale smaller logs and becomes more favorable as diameters increase.
- Scribner rule: historically based on diagrammed board layouts inside the log. It is often closer than Doyle on medium logs but still uses simplifying assumptions.
- International 1/4-inch rule: generally considered one of the most consistent traditional rules because it better accounts for taper and a realistic saw kerf.
None of these rules is universally “best” for every transaction. The best rule is the one specified by the buyer, local market, or timber sale contract. If you are comparing quotes from mills or log buyers, you must compare them on the same scale. A higher price per thousand board feet under one rule may still mean a lower total payment if that rule scales fewer board feet for your logs.
Comparison table: 16-foot log estimates by diameter
The following table shows calculated estimates for a 16-foot log using common formulas and rounded values. These figures illustrate how log rules diverge as diameter changes.
| Small-end diameter (in) | Doyle (bf) | Scribner (bf) | International 1/4-inch (bf) |
|---|---|---|---|
| 12 | 64 | 86 | 80 |
| 16 | 144 | 166 | 159 |
| 20 | 256 | 272 | 265 |
| 24 | 400 | 403 | 393 |
This table highlights a key practical reality: smaller logs are penalized more heavily under some rules, especially Doyle. As logs get larger, the differences among rules can narrow, though they never disappear entirely. For sellers, that means diameter distribution across a timber sale can significantly affect value depending on the rule used.
Comparison table: effect of log length on gross board feet
The next table shows gross cylindrical board-foot equivalents for a 12-inch average diameter log. These are geometric values, not scaled sawlog values, but they clearly show how length affects available wood volume.
| Average diameter (in) | Length (ft) | Cubic feet | Gross board feet equivalent |
|---|---|---|---|
| 12 | 8 | 6.28 | 75.4 |
| 12 | 12 | 9.42 | 113.1 |
| 12 | 16 | 12.57 | 150.8 |
| 12 | 20 | 15.71 | 188.5 |
Step-by-step example
Suppose you have a log that is 16 feet long, measures 16 inches at the small end inside bark, and 18 inches at the large end inside bark.
- Average diameter: (16 + 18) / 2 = 17 inches.
- Convert to feet: 17 inches / 12 = 1.4167 feet.
- Radius: 1.4167 / 2 = 0.7083 feet.
- Cross-sectional area: pi x 0.7083 squared = about 1.576 square feet.
- Cubic feet: 1.576 x 16 = about 25.22 cubic feet.
- Gross board feet: 25.22 x 12 = about 302.6 board feet.
Now compare that to log rules based on the small-end diameter of 16 inches:
- Doyle: about 144 board feet
- Scribner: about 166 board feet
- International 1/4-inch: about 159 board feet
Why is the gross geometric number so much higher? Because the gross estimate counts all wood in the log, while the log rules estimate recoverable board-foot lumber after losses in sawing. This is one of the most important distinctions for anyone new to log scaling.
Common mistakes when calculating board feet in a log
- Using outside-bark diameter without adjustment: bark inflates the measurement and can overstate yield.
- Measuring the wrong end: most scale rules rely on small-end diameter, not the large end.
- Confusing cubic feet with board feet: multiply cubic feet by 12 for gross board feet equivalent.
- Mixing log rules in comparisons: always compare buyer offers on the same rule.
- Ignoring defects: sweep, rot, shake, crook, and scars reduce usable lumber volume.
- Rounding too early: small rounding differences can become significant over many logs.
When to use each method
Use gross board feet when you want a clean physical volume estimate for planning, inventory, milling experiments, or comparing the raw size of logs. Use Doyle, Scribner, or International 1/4-inch when you need a market-oriented sawlog estimate tied to customary timber transactions. If you are a landowner selling logs, ask your buyer which rule is standard in your area and whether scale is measured at the mill or in the woods.
How defects and taper affect yield
No formula can perfectly predict sawmill recovery from every log. Straight, sound, low-taper logs often produce better recovery than poor-form logs with heavy sweep or internal defect. Veneer-quality logs can greatly outperform ordinary sawlogs in value, even if the board-foot scale is similar. Likewise, a log with metal, shake, or severe knots may produce fewer usable boards than a simple scale rule suggests. This is why professional timber appraisers and experienced buyers combine measurement with visual grading and species knowledge.
Species, market, and regional practice
Board foot calculations are only part of the pricing picture. Species, grade, accessibility, trucking distance, local mill demand, and seasonality all influence what a log is worth. In one region, oak sawlogs may be bought on Doyle scale; in another, softwood logs may be sold on Scribner or cubic volume. Portable mills may price by the hour rather than by board foot. Because of these differences, a good calculator is a decision support tool, not a substitute for a local market check.
Professional measurement tips
- Measure diameter inside bark whenever possible.
- Use a consistent tape or log rule stick.
- Record lengths to the nearest practical increment used by your buyer.
- Sort logs by species and quality before valuation.
- Separate gross geometric estimates from scaled yield estimates in your notes.
- Keep a log sheet so multiple logs can be totaled accurately.
Authoritative forestry resources
If you want deeper guidance on forestry measurement, timber sales, and log scaling, review materials from these authoritative institutions:
- USDA Forest Service
- Penn State Extension forestry resources
- Oregon State University Extension forestry guidance
Final takeaway
Calculating board feet in a log starts with a simple concept but becomes more nuanced once you factor in saw kerf, taper, slab loss, defects, and regional scaling conventions. For pure wood volume, convert cubic feet to gross board feet. For marketable sawlog yield, use the scaling rule that applies in your area. The calculator above helps you do both: it provides a quick gross estimate using actual dimensions and compares that number to the traditional log rules most often used in practice. If you are making a buying, selling, or milling decision, record your measurements carefully, use the same rule for every comparison, and verify local standards before finalizing value.