Log to Board Feet Calculator
Estimate lumber yield from a log using the three most common log rules: Doyle, Scribner, and International 1/4-inch. Enter diameter, log length, quantity, and your preferred rule to calculate total board feet instantly.
Results
Enter your values and click Calculate Board Feet to see yield estimates and a rule comparison chart.
Rule Comparison Chart
Expert Guide to Using a Log to Board Feet Calculator
A log to board feet calculator helps convert standing or felled log dimensions into an estimated lumber volume. In practical forestry, sawmilling, timber buying, and land management, this estimate is often the bridge between rough log dimensions and a meaningful production or sales number. A board foot is a unit of volume equal to a board that is 1 inch thick, 12 inches wide, and 12 inches long. That sounds simple, but converting round logs into board feet is not a direct geometry problem. Saw kerf, slab loss, taper, defects, and historical milling assumptions all affect how much lumber can actually be cut from a log. That is why different log rules exist.
This calculator is designed for fast estimation using the three most common North American log rules: Doyle, Scribner, and International 1/4-inch. Each rule uses a different method to estimate recoverable lumber. For buyers and sellers, understanding those differences matters because the same log can produce significantly different board foot estimates depending on which rule is used. If a woodland owner quotes a volume on the Doyle rule and a buyer expects International 1/4-inch values, the price discussion can go off course quickly.
What the calculator measures
The key inputs are the small-end diameter inside bark and the log length. Diameter is usually measured at the small end because that better reflects the limiting cross section for milling. Length is entered in feet. The calculator also allows a quantity field so you can estimate total board feet for multiple similar logs. If you are cruising timber in the field, this is useful when you have a stack of logs with matching classes or when you are building quick sale estimates.
- Diameter: Small-end diameter inside bark, usually in inches.
- Length: Merchantable log length in feet.
- Quantity: Number of similar logs to apply the estimate to.
- Rule: Doyle, Scribner, or International 1/4-inch.
Why there are different log rules
Log rules developed historically to estimate how many board feet of lumber a log could produce in a sawmill. Older rules were tied to assumptions about sawing technology, kerf width, slab loss, and what counted as usable lumber. These assumptions vary, so the formulas vary too. The result is that board foot estimates are not universal. They are a convention tied to a rule.
The Doyle rule is common in many hardwood markets, especially in parts of the eastern and central United States. It tends to underestimate volume in smaller logs because it assumes substantial slab and saw kerf loss. Scribner is another long-used rule and is generally less severe than Doyle on small and medium logs. International 1/4-inch was developed to better model actual sawmill recovery under a standardized set of assumptions, so it often produces higher and more consistent estimates across log sizes.
| Log Rule | General Tendency | Best Use Case | Important Caution |
|---|---|---|---|
| Doyle | Often lower on smaller logs | Common hardwood buying regions | Can heavily discount small diameters |
| Scribner | Middle-ground estimate | General sawlog scaling and regional markets | Still rule-based, not mill-specific recovery |
| International 1/4-inch | Often higher and more recovery-oriented | More technical yield estimation | May not match local buying custom |
How the formulas work in this calculator
This calculator uses standard estimating formulas for the three rules. They are practical field approximations and are widely used for quick planning:
- Doyle: BF = ((D – 4)2 × L) / 16
- Scribner: BF = ((0.79 × D2 – 2 × D – 4) × L) / 16
- International 1/4-inch: BF = (0.199 × D2 – 0.642 × D – 1) × (L / 4)
In these formulas, D is diameter in inches and L is log length in feet. Results are expressed in estimated board feet per log. The calculator multiplies that value by the number of logs to return total estimated board feet. Because board foot calculations are conventions and not exact predictions, actual lumber yield can still differ based on sweep, taper, defects, trim, and the sawmill setup.
Example calculation
Suppose you have one 16-inch diameter log that is 16 feet long. Using the approximate formulas above:
- Doyle: ((16 – 4)2 × 16) / 16 = 144 board feet
- Scribner: ((0.79 × 256 – 32 – 4) × 16) / 16 = 166.24 board feet
- International 1/4-inch: (0.199 × 256 – 0.642 × 16 – 1) × 4 = 158.69 board feet
That single example shows why rule selection matters. The difference between Doyle and Scribner on the same log is more than 22 board feet. In larger sales, those differences can become substantial and directly influence pricing, harvesting decisions, and contract language.
Comparison statistics for common diameters
The table below uses the same 16-foot log length across several diameters to illustrate how rule choice changes estimated volume. These figures are computed using the formulas implemented in this calculator.
| Diameter (in) | Doyle BF | Scribner BF | International 1/4-inch BF | Scribner vs Doyle |
|---|---|---|---|---|
| 12 | 64.00 | 85.76 | 104.08 | +34.0% |
| 16 | 144.00 | 166.24 | 158.69 | +15.4% |
| 20 | 256.00 | 272.00 | 238.80 | +6.3% |
| 24 | 400.00 | 403.04 | 344.42 | +0.8% |
Notice the trend: the Doyle rule penalizes small logs more heavily, so the percentage gap between Doyle and other rules is often largest in lower diameter classes. As diameter increases, the rules may converge somewhat, though they still do not match perfectly. For field negotiation, the practical lesson is simple: never compare board foot prices without confirming the rule used.
How to use a log to board feet calculator correctly
- Measure diameter accurately. Use the small-end diameter inside bark if your market standard calls for it. Diameter errors quickly affect board foot volume.
- Use merchantable log length. Make sure your length matches how the mill or buyer scales logs. Some markets rely on standard lengths and trim allowances.
- Select the same rule used in the sale. The most common mistake is comparing a Doyle quote to an International estimate.
- Apply quantity carefully. If your log pile varies in size, do not multiply one average log by total count unless the logs are truly similar.
- Treat the output as an estimate. Defects, sweep, crook, rot, and taper can reduce actual recoverable lumber.
Where board foot estimates are most useful
These calculators are especially valuable in timber sales, portable sawmill planning, forest inventory work, and educational forestry programs. A landowner may want to estimate how many board feet are in a stack of walnut or oak sawlogs before calling buyers. A portable mill operator may use board foot estimates to quote a custom milling job. Forestry students often use these calculators to compare historical log rules and understand why forest product measurement is not always straightforward.
In extension forestry and forest economics, board foot estimates also support rough valuation. If you know expected board feet and have a local price per thousand board feet, you can generate a preliminary gross value estimate. However, this should never replace a professional timber appraisal when significant money is involved. Grade, access, species mix, logging conditions, and local mill demand can shift sale value dramatically.
Limitations you should understand
- Board foot rules estimate potential, not guaranteed output.
- Actual sawmill recovery differs by equipment, kerf, optimization, and product mix.
- Defect deductions may be applied by professional scalers and buyers.
- Species does not change the board foot formula directly, but it strongly affects value.
- Some local markets use region-specific conventions or mill-specific scaling methods.
Board feet vs cubic volume
Board feet is a lumber-oriented measure, while cubic volume describes the actual three-dimensional wood content. Foresters often use cubic feet, cords, or biomass measures in inventory and management planning. Mills and log buyers may prefer board feet because it is closer to the lumber trade. That said, a cubic measure is often more neutral and less sensitive to saw rule assumptions. If you are comparing inventory reports, management plans, and mill quotes, always confirm whether the figures are in board feet, cubic feet, or cords.
Authority sources and further reading
If you want to go deeper into log rules, timber measurement, and wood products, these sources are reliable starting points:
- Penn State Extension for educational forestry resources and timber measurement guidance.
- U.S. Forest Service for forest products, utilization, and measurement references.
- University of Minnesota Extension for timber sales, woodland management, and measurement education.
Frequently asked questions
Is a board foot the same as a cubic foot?
No. One board foot equals 144 cubic inches, which is one-twelfth of a cubic foot. Board feet are commonly used in lumber and sawlog contexts, while cubic feet are used more broadly in forest inventory and volume studies.
Which rule is most accurate?
There is no single answer for every situation. International 1/4-inch is often considered more technically representative of sawmill recovery assumptions, but local markets may still transact on Doyle or Scribner. The most useful rule is usually the one that matches the buyer, contract, and regional standard.
Why does my sawmill output not match the calculator?
Because actual recovery depends on many variables beyond diameter and length. Taper, defect, sweep, trim loss, kerf width, sawing pattern, and target product dimensions all influence output. A calculator gives a fast benchmark, not a guaranteed tally.
Should I average all my logs into one input?
Only if the logs are genuinely similar. If your logs vary widely by diameter or length, calculate them by groups or individually for a more dependable estimate. A few large logs can skew the average and distort total volume.
Final takeaway
A log to board feet calculator is one of the simplest but most useful tools in forestry and sawmill planning. It converts field measurements into a practical estimate you can use for budgeting, quoting, sale prep, and yield comparison. The most important habit is to match the calculation rule to the market standard you are working with. If you do that, and if you measure diameter and length carefully, the calculator becomes a powerful decision-making shortcut. Use it to compare Doyle, Scribner, and International 1/4-inch side by side, then confirm assumptions before any high-value transaction.