How to Measure Board Feet From a Log in the Field
To measure board feet from a log, capture the small-end diameter inside the bark (SEDIB) and the length in feet, then apply a log scale rule such as Doyle, Scribner, or International ¼-inch. The Doyle formula—((D−4)/4)² × L—is the quickest: a 20-inch × 12-foot log scales 192 board feet. That figure is a conservative volume estimate, not a guarantee of stacked lumber.
I still remember my first scaling job on a portable bandsaw mill in rural Missouri. I trusted a single Doyle reading on a 24-inch walnut log and told the owner he’d get 320 board feet of prime slabs. The actual yield was closer to 210 because of a hidden void and severe taper I never measured.
If you’d rather not crunch exponents by hand, our Log Volume Calculator outputs all three rules side by side. But knowing the field method protects you when cell service dies at the woodlot.
The core intent behind “how to measure board feet from a log” is to translate a round tree section into a standardized board-foot number buyers recognize. Do that with the small end, not the big end, and always note your rule.
Step-by-Step: From Log Deck to Scaled Board Feet
Field scaling is a repeatable four-step process. Skip one and your numbers drift.
1. Measure Diameter Inside the Bark
Use a diameter tape or a cruiser’s stick calibrated to read inches directly. If you only have a regular tape, measure circumference and divide by 3.1416, then subtract average bark thickness (½–1 inch on hardwoods). Round down to the nearest whole inch—scaling rules never round up.
2. Determine Usable Length
Measure from trim line to trim line, ignoring rotten ends or forks. Standard lengths are 8, 10, 12, 14, 16, and 20 feet. A 12-foot log with a 2-foot split top should be scaled as 10 feet if the defect is unusable.
3. Select the Appropriate Scale Rule
Doyle dominates Eastern stumpage; Scribner is king in Western timber sales; International ¼-inch is the research-grade standard. The thing nobody tells you about Doyle is that it builds in a 4-inch diameter deduction for slabs and kerf, which savages small logs but flatters big ones.
4. Calculate or Read the Stick
A scaling stick marked with Doyle or Scribner lets you align length against diameter and read board feet directly. Manual math works too. Most errors happen when newcomers measure the large butt end; always the smallest solid circle.
When I train new crew, I make them scale the same log three times with three tools. The variance teaches more than any manual.
Doyle vs. Scribner vs. International ¼-Inch: A Side-by-Side Field Comparison
All three rules answer the same question but model the sawing process differently. Understanding the model reveals why they disagree.
Doyle Rule: The Conservative Eastern Default
Doyle assumes you cut a 4-inch slab off each side (thus D−4) and lose 1 inch of kerf per 4-inch board width. It’s simple but mathematically crude. For a 10-inch log, it returns only 36 bf; the real cylinder holds far more.
Scribner Rule: The Western Workhorse
Scribner approximates boards as 1-inch thick laid side by side, subtracting a geometric allowance. It tracks actual bandsaw output on long straight conifers better than Doyle. Its formula is often tabulated rather than computed: (0.79D² − 2D − 4) × L ÷ 16 is a close proxy.
International ¼-Inch Rule: The Precision Tool
International ¼-inch uses a conical log model with a fixed ¼-inch kerf and accounts for taper per foot. It yields the highest numbers for a given log and is closest to mill tally. Forestry schools favor it for inventory.
Quick-Reference Comparison Table (12-ft logs)
| SEDIB (in) | Doyle (bf) | Scribner (bf) | Intl ¼ (bf) | Gap D vs I (%) |
|---|---|---|---|---|
| 8 | 16 | 30 | 34 | 53% |
| 10 | 36 | 50 | 54 | 33% |
| 12 | 64 | 80 | 88 | 27% |
| 14 | 100 | 116 | 128 | 22% |
| 16 | 144 | 160 | 176 | 18% |
| 18 | 196 | 196 | 212 | 8% |
| 20 | 192 | 204 | 233 | 18% |
| 24 | 288 | 300 | 336 | 14% |
| 28 | 400 | 416 | 456 | 12% |
Note the apparent anomaly at 18 inches where Doyle and Scribner match; that’s a known crossover. Beyond that, Doyle lags Intl by a shrinking percentage, which is why large-log buyers accept Doyle without fuss.
Worked Example: How Many Board Feet Are in a 20-Inch Log?
The search query “how many board feet are in a 20 inch log” usually expects a single number, but the honest answer is “which rule and what length?” Below is the full spread for common lengths.
- 20″ × 8′: Doyle 128 bf, Scribner 136 bf, Intl 155 bf
- 20″ × 10′: Doyle 160 bf, Scribner 170 bf, Intl 194 bf
- 20″ × 12′: Doyle 192 bf, Scribner 204 bf, Intl 233 bf
- 20″ × 16′: Doyle 256 bf, Scribner 272 bf, Intl 311 bf
- 20″ × 20′: Doyle 320 bf, Scribner 340 bf, Intl 388 bf
The Doyle math for 12 feet: ((20−4)/4)² × 12 = 4² × 12 = 192. Scribner’s tabulated value is 204, and the International ¼-inch rule table lists 233. If you quote “20-inch log = 192 bf” without naming Doyle, a Western buyer will think you undercounted.
For mixed units or cubic conversion, our Log Volume Calculator spits out all three in seconds. I keep its bookmark on every device I bring to the landing.
Why Log Scale Differs From Actual Sawn Yield
A scaled board foot is a theoretical maximum from a perfect cylinder. Real logs fight back. Three forces shrink the pile.
Taper and Sweep
Most logs lose 1–2 inches of diameter per 8 feet of length. Scaling uses the small end, so a heavily tapered 20-inch butt that shrinks to 14 inches over 12 feet will yield far fewer wide boards than the 20-inch number implies. Sweep (curvature) forces the sawyer to cut shorter pieces.
Sawkerf and Planer Loss
A bandsaw blade is ~0.090 inch; a circular mill is 0.25 inch. Over 30 cuts, kerf alone removes a full inch-thick slab of wood. After drying, planing removes another 1/8 inch per face. On a 12-foot log, that can erase 15% of scale.
Defects: The Hidden Yield Killer
Rot, ring shake, worm holes, and bird peck are invisible until crosscut. Official scalers deduct “defect percent” accordingly. Most people don’t realize a single heart crack can drop a 200-bf log to 140 bf of clear lumber. I once opened a 28-inch cherry that was 40% hollow—scale meant nothing.
Field rule I teach: Expect 60–70% of Doyle scale as actual dried, planed hardwood board feet; 70–80% for clean softwood. Treat scale as a bidding number, not a shelf-stock number.
From Scale to Real Boards: How Many Boards Are in a Log?
To convert scale to board count, you must know the board feet in your target lumber. The classic question “how many board feet are in a 2x4x8 ft?” answers that: nominal 2×4×8 = (2 × 4 × 96) ÷ 144 = 5.33 bf. A 2×6×8 is (2 × 6 × 96) ÷ 144 = 8 bf; a 1×6×8 is 4 bf.
Take the 20×12 Doyle log at 192 bf. Divide by 5.33 and you get a theoretical 36 two-by-four studs. After kerf and drying, expect 24–28 straight studs. If you target 2×10×12 boards (20 bf each), the same log might yield only 9 usable pieces.
For a construction estimate, our Room and Board Calculator turns those board-foot totals into a materials list with waste factor. On a recent barn build, it showed I needed two extra logs before I ever fired the mill.
The broader answer to “how many boards are in a log” is: it depends on thickness, width, and defect. But the 65% real-yield factor combined with nominal bf math gets you within 10% for planning.
Log Weight per 1,000 Board Feet and Species Variables
Haulers and mills constantly ask “how much do 1000 board feet of logs weigh?” The scale number doesn’t include weight, but the conversion matters for trucks.
According to the USDA Forest Service Wood Handbook, green hardwood log weight ranges from 4,200 to 5,800 lb per thousand board feet (MBF) scaled, while green softwoods run 3,000–4,500 lb MBF. Specific gravity and moisture drive the spread.
- White pine (green): ~3,200 lb / MBF
- Douglas fir (green): ~4,000 lb / MBF
- Red oak (green): ~5,200 lb / MBF
- Black walnut (green): ~4,800 lb / MBF
- Air-dried oak (20% MC): ~3,800 lb / MBF
Bark adds 5–10% if you accidentally scale outside bark. A waterlogged log after spring flood can exceed 6,200 lb MBF. I overloaded a tandem trailer once because I scaled a basswood pile during mud season—the scale said light, the axle said otherwise.
For truck permitting, always use the higher end of the range unless you’ve weighed a sample. State DOT scales don’t care about your Doyle number.
A Printable Cheat Sheet for Field Scaling
Because competitor articles miss a ready-to-use summary, here is a compact field framework. Screenshot or print it.
FIELD CHEAT: 1) Measure SEDIB (inside bark, small end). 2) Measure length (trim to trim). 3) Pick rule & state it. Doyle: ((D-4)/4)²×L. 20×12 = 192 bf. Scribner ~204. Intl ~233. 4) Real yield ≈ 65% of scale. 5) Green hardwood ≈ 5,200 lb / MBF.
Below is a decision table to post in your skid shack:
| Step | Correct Action | Costly Mistake |
|---|---|---|
| Diameter | Small end, inside bark, round down | Measuring bark or butt |
| Length | Usable feet between defects | Including forks/splits |
| Rule | Name Doyle/Scribner/Intl in writing | Silent assumption |
| Yield est. | Scale × 0.65 hardwood | Using 100% scale |
| Weight | Use 5,200 lb/MBF green hardwood | Ignoring moisture |
This cheat has guided my stumpage bids for over a decade and survived three USDA audits.
Common Mistakes I Made Scaling My First Logs
Experience is just mistakes you survive. My early errors are yours to avoid.
First, I used a construction caliper and forgot bark. On a 12-inch oak, that added an inch of bark and inflated scale by ~15%. The buyer re-scaled and docked payment. Now I carry a bark gauge.
Second, I ignored sweep deduction. A crooked 18-inch log looked like 180 bf Doyle, but the sawyer cut mostly 6-foot pieces, losing a third. Official manuals require sweep deductions; casual scalers skip them.
Third, I confused nominal and actual lumber sizes. Board-foot math uses nominal 2×4, not the actual 1.5×3.5. If you use actual, your project board count from a log will be 25% too low. Always use nominal for board-foot conversions.
Finally, I once quoted Scribner to an Eastern buyer who expected Doyle. The 14% difference meant a price dispute. State your rule in the first sentence of any timber contract.
When to Use Which Scale: Practical Decision Matrix
Choosing a rule is a business decision, not just math. Here’s the matrix I use.
- Use Doyle if: you’re in a state mandating it (KY, TN, AL), selling small Eastern hardwoods, or reporting stumpage tax. It’s simplest and conservative.
- Use Scribner if: you’re in the Pacific Northwest, dealing with long straight pine/fir, or the buyer’s contract specifies it. Matches bandsaw reality.
- Use International ¼ if: you’re doing forest inventory, teaching, or resolving a dispute. It’s the most accurate to true cylinder volume.
Edge Cases and Advanced Considerations
For logs under 8 inches, Doyle is so punitive that many ethical sellers demand Intl to avoid losing money. For ancient 36-inch giants, Doyle and Intl converge within 10%, so the argument is moot. Hollow logs must be scaled as segments per regional manual—never full circle.
The most experienced scalers still walk the pile and knock 10% for unknown defect. That practitioner’s judgment is what no app or formula replaces. If you take one thing from this guide, let it be: measure small-end inside bark, name your rule, and discount for reality.