Board Feet From a Log Calculator
Estimate lumber yield from a single log or a batch of logs using common North American log scaling rules. Enter the small end diameter inside bark, choose log length, select a rule, and compare the estimated board feet side by side.
Estimated results
Enter your log dimensions and click Calculate Board Feet to see your estimate.
Expert Guide to Calculating Board Feet From a Log
Calculating board feet from a log is one of the most important skills in timber cruising, small sawmill planning, woodland management, and log buying. Whether you are a landowner estimating stumpage, a sawyer planning production, or a woodlot manager comparing sale options, the basic goal is the same: estimate how much sawn lumber a log can produce. A board foot is the standard unit for that estimate, but the exact answer depends on the scale rule you use, how carefully the log is measured, and what assumptions are built into the rule.
At its simplest, a board foot is a volume measurement equal to 144 cubic inches of wood. In practical lumber terms, that is a board that measures 1 inch thick by 12 inches wide by 12 inches long. Logs are not rectangular boards, though. They taper, they may lose wood to slabs and saw kerf, and they often contain defects that reduce recovery. Because of that, forestry and sawmilling rely on log rules to convert a measured diameter and length into an estimated amount of lumber.
Why board foot estimates matter
Board foot estimates affect real business decisions. They are used to price logs, compare buyers, estimate harvest revenue, determine trucking loads, and forecast mill output. If two buyers use different rules, the same pile of logs can produce very different board foot totals on paper. That is why understanding the method behind the number is just as important as understanding the number itself.
- Landowners use board foot estimates to compare offers and understand the potential value of standing timber.
- Sawmills use them to plan lumber yield, inventory, and production schedules.
- Foresters use them in timber cruises, management plans, and sale preparation.
- Log buyers use them to set prices, sort logs by class, and estimate shipment value.
The three most common log scale rules
In much of the United States, the most common board foot rules are Doyle, Scribner, and International 1/4-inch. All three use the small end diameter inside bark and log length, but they do not estimate yield the same way.
- Doyle rule is simple and widely recognized, but it tends to understate smaller logs and becomes more favorable as diameters get larger.
- Scribner rule is based on diagramming boards in a log cross section and is a long standing commercial rule in many regions.
- International 1/4-inch rule attempts to account more realistically for taper and saw kerf. Many foresters consider it one of the more consistent scaling rules across a wide diameter range.
Because these rules model lumber recovery differently, they are not interchangeable. A 16 inch by 16 foot log will not produce the same board foot estimate under each rule, even though the physical log has not changed. If you are buying or selling logs, always verify which rule is being used.
How to measure a log for board feet
Reliable estimates start with reliable measurements. The standard field measurement for scale rules is the small end diameter inside bark, usually shortened to DIB, plus the merchantable log length in feet. For the most consistent results, measure carefully and stay consistent from log to log.
- Measure the diameter at the small end of the log, not the butt end.
- If scaling inside bark, subtract bark thickness as required by your local practice.
- Measure length along the usable merchantable section of the log.
- Use the same rounding rules required by the buyer, forester, or mill.
- Watch for sweep, crook, rot, or heavy defect that may reduce actual recovery below the log rule estimate.
Common formulas used in calculators
The calculator above uses standard formula approximations for the three common rules. These formulas are useful for quick estimation and education. In some regions, buyers may use printed scale sticks, regional tables, or specific rounding conventions, so final sale figures may differ slightly.
In these formulas, D is the small end diameter inside bark in inches and L is the log length in feet. The output is estimated board feet. If a formula gives a negative value for a very small log, the practical result is treated as zero because such a log has no meaningful board foot scale under that rule.
Comparison table for a 16 foot log
The table below shows how common scaling rules can diverge. These are actual calculated values for a 16 foot log using the formulas above. The difference is not a math error. It is the expected result of using different log rules.
| Small End Diameter | Doyle BF | Scribner BF | International 1/4 BF | Highest vs Lowest Difference |
|---|---|---|---|---|
| 12 inches | 64.0 | 85.8 | 95.6 | 31.6 BF |
| 16 inches | 144.0 | 166.2 | 179.2 | 35.2 BF |
| 20 inches | 256.0 | 272.0 | 288.4 | 32.4 BF |
| 24 inches | 400.0 | 403.0 | 423.0 | 23.0 BF |
This table highlights a point many woodland owners miss the first time they compare scale tickets. The smaller the log, the more dramatic the difference can be, especially when Doyle is compared with International 1/4-inch. If your timber sale includes many smaller sawlogs, the selected log rule can have a meaningful effect on apparent volume and sale comparison.
How log length changes board feet
Length matters too. Longer logs typically scale more board feet, but the increase is not always perfectly proportional under every rule. The next table uses a 16 inch small end diameter and shows the effect of changing only the log length.
| Log Length | Doyle BF | Scribner BF | International 1/4 BF | Observation |
|---|---|---|---|---|
| 8 feet | 72.0 | 83.1 | 83.6 | Short logs reduce total scale quickly. |
| 12 feet | 108.0 | 124.7 | 129.9 | Mid length logs often balance handling and yield. |
| 16 feet | 144.0 | 166.2 | 179.2 | Common standard for many mills and log buyers. |
| 20 feet | 180.0 | 207.8 | 231.8 | Longer logs can increase scale but may limit handling options. |
Step by step example
Suppose you have a log with a small end diameter inside bark of 18 inches and a merchantable length of 16 feet. You want to estimate board feet under all three rules.
- Measure the small end diameter inside bark: 18 inches.
- Measure the log length: 16 feet.
- Apply the Doyle formula: ((18 – 4)² × 16) / 16 = 196 board feet.
- Apply the Scribner formula: ((0.79 × 18²) – (2 × 18) – 4) × 16 / 16 = 215.96 board feet.
- Apply the International 1/4-inch formula: approximately 232.31 board feet.
If you had 10 similar logs, the batch estimate would simply be the per log result multiplied by 10. That means roughly 1,960 Doyle board feet, 2,159.6 Scribner board feet, or 2,323.1 International 1/4-inch board feet. The physical pile of logs has not changed. Only the rule has changed.
Board feet versus cubic volume
Many people assume board feet are the same as cubic volume. They are not. Cubic volume measures wood space directly. Board foot scale rules estimate potential lumber yield after sawing assumptions are applied. A log can contain a certain amount of cubic wood and still produce different board foot outcomes depending on kerf, taper, edging, trim allowance, and rule design. That is why some modern inventory systems prefer cubic measures for biological growth estimates while mills and timber markets still often use board feet for product and value discussions.
Factors that can change actual lumber recovery
No log rule can perfectly predict what happens at the sawmill. Real recovery depends on more than diameter and length. If you are using board foot estimates to make a financial decision, keep these practical factors in mind:
- Taper: Logs that lose diameter rapidly from butt to top can recover differently than the rule predicts.
- Defect: Rot, seams, knots, cracks, metal, and stain can reduce usable lumber.
- Sweep and crook: Curved logs are harder to saw efficiently.
- Sawmill technology: Thin kerf and optimization systems may improve actual recovery compared with older assumptions.
- Target product mix: Sawing for grade lumber, cants, timbers, or specialty slabs changes yield patterns.
- Bark deductions and trim: Local market practice can shift board foot scale before the log reaches the mill.
Best practices for landowners and small mills
If you are selling timber or buying logs, the safest approach is to standardize your measurement method and ask direct questions. Find out exactly which rule is being used, how diameters are rounded, whether scaling is inside or outside bark, and how defects are handled. If you compare offers from multiple buyers without confirming the log rule, you may be comparing apples to oranges.
For small mills, it can be useful to keep both a board foot estimate and an actual lumber tally after sawing. Over time, this lets you compare your own recovery rates with the assumptions built into each log rule. That feedback can improve quoting, purchasing, and production planning. Mills that process a lot of smaller diameter logs often notice especially large differences between Doyle and International 1/4-inch outcomes.
Authoritative resources for further reading
If you want to verify scaling practices, review forestry measurement guidance, or study regional timber marketing methods, these sources are useful starting points:
- U.S. Forest Service for forest measurement references, timber sale information, and technical forestry publications.
- Penn State Extension for woodland management, timber sales, and practical guidance for landowners.
- Purdue Extension for forestry outreach, log measurement education, and woodland economics.
Final takeaway
Calculating board feet from a log is straightforward once you understand the measurement inputs and the rule being applied. Measure the small end diameter inside bark, measure merchantable length, choose the correct scale rule, and calculate the estimate. The hard part is not the arithmetic. The hard part is recognizing that different log rules can give materially different answers for the same log. When that difference affects pricing, contracts, or harvest decisions, clarity matters.
Use the calculator above to estimate your logs quickly, compare Doyle, Scribner, and International 1/4-inch results, and visualize how your selected rule changes total volume. For field estimates and planning, it is an excellent starting point. For a timber sale, always confirm the buyer’s scaling method and, when the value is substantial, work with a professional forester.