How do I use this log board foot calculator?

Enter the small-end diameter inside bark and the log length, then choose Doyle, Scribner, or International 1/4-inch. Turn on comparison to see all three log scale results for the same diameter and length.

What is the Doyle log scale?

The Doyle scale is a traditional log rule used to estimate board feet from a log’s diameter and length. It’s simple and widely used in many areas, especially for hardwoods. A common version is: BF = (D − 4)² × L ÷ 16, where D is DIB in inches and L is length in feet.

Which log rule is most accurate?

International 1/4-inch is often considered the most consistent because it includes taper and kerf assumptions. Scribner is usually a mid-range estimate, and Doyle can underestimate small logs. The “right” rule is the one your region or buyer uses—prices are often adjusted to match local custom.

How many board feet are in a 12-inch log?

It depends on the log length and the rule. For a 12" DIB × 16' log, Doyle estimates 64 BF. Scribner and International often estimate higher for the same log. Use the comparison toggle to see all three rules side by side.

What is DIB (diameter inside bark)?

DIB means the diameter measured inside the bark, usually at the small end of the log. Many scaling rules assume DIB. If you measure outside bark, the estimate can be high—especially with thick bark species—unless you adjust for bark thickness.

Why does Doyle underestimate small logs?

Doyle builds in a large allowance for slabs and edging. On small logs, that allowance removes a big share of the usable wood, so the scale can come out low compared to what a modern mill can actually saw. That’s why Doyle is often viewed as buyer-friendly on small diameters.

What is overrun in log scaling?

Overrun means the mill produces more lumber than the scale estimate. Underrun means it produces less. Overrun/underrun happens because rules are estimates and real yield depends on log quality, taper, mill equipment, and how the log is sawn.

Can I calculate board feet for standing trees?

Not with this tool. Standing-tree volume uses different methods (like taper equations or local volume tables) and additional measurements such as diameter at breast height (DBH) and merchantable height. This calculator is designed for cut logs measured as DIB × length.

Log Board Foot Calculator — Doyle, Scribner & International Log Scale

Enter the small-end diameter (DIB) and log length to estimate board feet in a log. Compare Doyle, Scribner, and International 1/4" rules side by side.

Log Scale Calculator

Diameter + Length

Doyle / Scribner / International

Diameter (DIB)

6"12"48"

Measure at the small end, inside the bark.

Length

Log rule

Show rule comparison

See Doyle, Scribner, and International results side by side.

Estimated yield

64.00

Board Feet

12" DIB 16' length Doyle

Rule comparison

Doyle

64.00BF

Scribner +34.0%

85.76BF

International 1/4" +51.4%

96.92BF

Percent values show the difference compared to Doyle.

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How to Measure a Log for Board Feet

The inputs are simple, but measuring the right spot matters. Use DIB (diameter inside bark) at the small end for the most consistent results.

Tip: If the bark is thick or rough, measure inside bark (DIB) when you can.

1
Step 1 — Measure the Small-End Diameter (DIB)
Measure the diameter on the small end of the log, inside the bark. If you only have outside-bark diameter, your estimate may run high.
2
Step 2 — Measure the Log Length
Measure the usable length in feet (for example, 8–20 ft). Use the same length you expect the mill to scale.
3
Step 3 — Pick a Log Rule
Different regions use different rules. Doyle is common in the eastern U.S., Scribner is often used as a mid-range estimate, and International 1/4" is generally the most consistent.

How to Calculate Board Feet with the Scribner Log Rule

Quick formula and worked example for the Scribner log scale — the official rule used on U.S. National Forest timber sales.

To calculate board feet with the Scribner log rule, measure the small-end diameter inside bark (D, in inches) and the log length (L, in feet), then apply the Decimal C approximation: BF = (0.79·D² − 2·D − 4) × L ÷ 16. A 12-inch DIB × 16-foot log scales to (0.79 × 144 − 24 − 4) × 16 ÷ 16 ≈ 85.8 board feet — about 34% higher than the Doyle rule predicts for the same log.

More Scribner worked examples

10" × 16' log: (0.79 × 100 − 20 − 4) × 1 ≈ 55 BF (vs Doyle 36 BF). 16" × 16' log: (0.79 × 256 − 32 − 4) × 1 ≈ 166 BF (vs Doyle 144 BF). 20" × 12' log: (0.79 × 400 − 40 − 4) × 0.75 ≈ 204 BF. Most U.S. Forest Service timber sales scale in Scribner Decimal C — always confirm the rule your buyer or mill uses before quoting.

Understanding Log Scaling Rules

Log rules estimate how much lumber you can saw from a log. The same log can scale very differently depending on the rule.

Doyle Log Rule

A simple, traditional rule that’s widely used. It often underestimates small logs because the slab allowance is large. Buyers and sellers often price with that bias in mind.

Scribner Log Rule

Originally based on boards drawn from logs. It can be closer than Doyle on mid-size logs, but it doesn’t fully account for taper and can vary from modern mill yield.

International 1/4-Inch Rule

Often considered the most consistent of the three. It’s based on saw-kerf and taper assumptions and tends to track modern sawn yield better than Doyle.

Doyle, Scribner & International 1/4" Log Rules — Side-by-Side Deep Dive

Each log rule estimates board feet differently. Below are the formulas, where each rule is used, when it over- or under-estimates yield, and how a 12-inch DIB × 16-foot log scales under each.

Doyle Log Rule

Formula: BF = (D − 4)² × L ÷ 16; D = small-end DIB in inches, L = log length in feet. The 4-inch deduction represents slab and edging loss.
12" × 16' log: (12 − 4)² × 16 ÷ 16 = 64 board feet.
Origin: Devised by Edward Doyle in the early 1800s as a simple mental-math rule for hardwood log buyers. The 4-inch slab allowance baked in the typical losses for circular-saw mills of that era.
Where it's used: The standard log scale across the eastern and southern United States — Tennessee, Kentucky, Alabama, Mississippi, the Ohio Valley, and most Appalachian hardwood markets quote prices in Doyle board feet.
Estimation bias: Under-estimates small logs because the 4-inch slab allowance removes a large share of usable wood. A 10" × 16' log scales only 36 BF in Doyle. Tracks modern mill yield reasonably well once diameter clears about 20 inches.

Scribner Log Rule

Formula (Decimal C approximation): BF = (0.79·D² − 2·D − 4) × L ÷ 16; Continuous approximation of J.M. Scribner's 1846 board-diagram tables, published by University of Tennessee Extension PB1650.
12" × 16' log: (0.79 × 144 − 24 − 4) × 16 ÷ 16 ≈ 85.8 board feet — about 34% more than Doyle.
Origin: Created by J.M. Scribner in 1846 by literally drawing 1-inch boards inside a circle of each diameter and counting how many fit. Decimal C rounds results to the nearest 10 board feet and is the most widely tabulated variant.
Where it's used: The official log rule of the U.S. Forest Service on national forests and most timber sales in the Pacific Northwest, Inland West, and Rocky Mountain regions. Common for softwood saw logs.
Estimation bias: Closer to actual mill yield than Doyle on mid-size logs from 12-20 inches. Under-estimates long logs because the original tables ignore taper above 16 feet. Slightly low under modern thin-kerf sawing.

International 1/4-Inch Log Rule

Formula (Grosenbaugh 1948 polynomial): BF ≈ 0.04976·L·D² + 0.00622·L²·D − 0.18548·L·D + …; Continuous polynomial fit that explicitly assumes 1/4-inch saw kerf and 1/2-inch taper per 4 feet of length.
12" × 16' log: ≈ 96.9 board feet — roughly 51% higher than Doyle for the same log.
Origin: Derived by Judson F. Clark in 1906 and re-fit by L.R. Grosenbaugh in 1948. The only mainstream rule that explicitly models log taper and saw kerf instead of treating logs as straight cylinders.
Where it's used: Used by the U.S. Forest Service for forest inventory and growth studies, by state forestry agencies across the Lake States and Northeast, and as the reference rule in most forest-mensuration textbooks.
Estimation bias: Generally regarded as the most consistent of the three rules. Tracks modern band-saw and thin-kerf yield within a few percent across diameters from 8" to 30". Slightly high on very small logs because the taper allowance is modest.

Same 12" × 16' log: Doyle 64 BF → Scribner 85.8 BF → International 1/4" 96.9 BF. The rule you scale by can change the apparent yield by 50% — always confirm which rule your buyer or mill uses before pricing.

Log Board Feet Quick Reference

Common diameters × lengths. Switch rules to see how estimates change.

Diameter (in)	8'	10'	12'	14'	16'
8"	8.00	10.00	12.00	14.00	16.00
10"	18.00	22.50	27.00	31.50	36.00
12"	32.00	40.00	48.00	56.00	64.00
14"	50.00	62.50	75.00	87.50	100.00
16"	72.00	90.00	108.00	126.00	144.00

8" Diameter

DIB at small end

8.00

10'

10.00

12'

12.00

14'

14.00

16'

16.00

10"

10" Diameter

DIB at small end

18.00

10'

22.50

12'

27.00

14'

31.50

16'

36.00

12"

12" Diameter

DIB at small end

32.00

10'

40.00

12'

48.00

14'

56.00

16'

64.00

14"

14" Diameter

DIB at small end

50.00

10'

62.50

12'

75.00

14'

87.50

16'

100.00

16"

16" Diameter

DIB at small end

72.00

10'

90.00

12'

108.00

14'

126.00

16'

144.00

All values assume DIB at the small end and length in feet. Results are estimates, not mill guarantees.

Common Mistakes to Avoid

Log scaling is sensitive to measurement details.

Measuring outside bark instead of DIB

Most log rules assume DIB (diameter inside bark) at the small end. Using outside-bark diameter can overestimate yield—especially on thick-bark species.

Measuring the wrong end

Measure the small end, not the large end. Using the large end can inflate estimates because taper is real.

Using the wrong rule for your region

Prices and expectations are tied to local rules. Confirm whether your buyer uses Doyle, Scribner, or International 1/4" before you compare numbers.

Disclaimer

This calculator provides an estimate for informational purposes. Real-world lumber yield depends on species, defects, taper, mill equipment, kerf, and local scaling practices. Always confirm the log rule, measurement method (DIB vs outside bark), and rounding conventions with your buyer or mill.

Sources

University of Tennessee Extension — PB1650: Understanding Log Scales and Log Rules (Scribner & International formulas).
USDA Forest Service — National Forest Log Scaling Handbook (measurement and scaling guidance).
International 1/4" rule coefficients are commonly published as a continuous-length approximation (Grosenbaugh-style polynomial fit to rule tables).

❓

Frequently Asked Questions

You measure the small-end diameter inside bark (DIB) in inches and the log length in feet, then apply a log rule. For example, the Doyle rule uses: BF = (D − 4)² × L ÷ 16. Other common rules include Scribner and International 1/4-inch, which often give higher estimates for the same log.

Log Board Foot Calculator — Doyle, Scribner & International Log Scale

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Board Foot Calculator

Board Feet to Square Feet

Cost Estimator

Multi-Board Calculator

How to Measure a Log for Board Feet

Step 1 — Measure the Small-End Diameter (DIB)

Step 2 — Measure the Log Length

Step 3 — Pick a Log Rule

How to Calculate Board Feet with the Scribner Log Rule

Understanding Log Scaling Rules

Doyle Log Rule

Scribner Log Rule

International 1/4-Inch Rule

Doyle, Scribner & International 1/4" Log Rules — Side-by-Side Deep Dive

Doyle Log Rule

Scribner Log Rule

International 1/4-Inch Log Rule

Log Board Feet Quick Reference

Common Mistakes to Avoid

Measuring outside bark instead of DIB

Measuring the wrong end

Using the wrong rule for your region

Disclaimer

Sources

Frequently Asked Questions