Log Board Feet CalculatorDoyle · Scribner · International 42 — all three scales, side by side

Everything you need to know about scaling a log

Ask five sawmill operators how to scale a log and you'll get six opinions — but they'll all agree on two things: you measure the small-end diameter, and the scale matters. A log board feet calculator is the bridge between those two immutable facts and a real dollar amount, because board feet aren't an academic concept — they're how loggers get paid, how sawmills price their output, and how wholesale lumber buyers compare hardwood quotes across regions.

The three scales you see here — Doyle, Scribner, and International 4-inch — have been fighting for market share since the mid-1800s, and they still matter because there is no single US standard. Doyle dominates the South, Midwest, and West. Scribner holds sway in the Northeast and Appalachian hardwood country. International 42 is the export and Canadian standard. If you're buying logs in Georgia and quoting them in New York, or selling to a Canadian mill, you absolutely must know which scale your buyer expects — swapping Doyle for International on a load of hardwood can change the invoice by 10–25%.

How to measure a log for board feet — the Forest Service method

Scaling a log sounds straightforward: measure diameter, measure length, plug into a formula. In practice there are four common mistakes that create huge cost mismatches, and every one of them is avoidable if you follow the USDA Forest Service procedure published in the Log Scaling and Timber Cruising Handbook:

1. Measure small-end diameter inside bark. The small end of the merchantable log — where the trunk tapers down to the point it becomes too small to saw — is the critical measurement. Not the butt end, not the middle, and absolutely not outside the bark. Bark thickness varies by species and season: young oak might have 0.5-inch bark, mature Douglas Fir can have 1-inch bark or more. Scaling outside bark gives you a BF number that's 10–20% high.

2. Use calipers or average two perpendicular measurements. Trees aren't perfectly round. The Forest Service recommends taking two diameter measurements at right angles and averaging them for a "mean diameter." For rough field work, a cloth tape measure around the circumference gives you π × D, so D = circumference ÷ π to ±0.2 inches — good enough for most commercial scaling.

3. Length to the nearest foot, merchantable section only. Measure from the small end all the way to where the log reaches minimum merchantable diameter (usually 6 inches for framing softwoods, 8–10 inches for veneer hardwoods) or hits a significant knot or branch that disqualifies lumber production. Don't include cull sections — everyone knows a log with a big rot pocket on one end, and every scale assumes you're using only the merchantable length.

4. Know your buyer's scale before you measure. This is the big one. Doyle, Scribner, and International all use the same diameter and length inputs — they just apply different waste assumptions. A 14-inch × 12-foot log scales to 81 Doyle BF, 127 Scribner BF, or 132 International BF. If you quote that load at Scribner to a Doyle buyer, you're effectively overcharging by 57%. If you quote Doyle to an International buyer, you're selling yourself short by about 40%.

Why each scale gives a different number — the waste assumption

Every log scale is really a sawmill waste model. The formulas all start with D² × L, which is proportional to the actual cubic volume of the log (since volume of a cylinder ≈ π/4 × D² × L, and all three scales factor out the constants differently). The difference is how each model subtracts the inevitable waste that happens during sawing:

Doyle: The (D − 4)² deduction is equivalent to losing a 2-inch slab on each side of the log to get down to a square'ish cant that a head saw can actually cut lumber from. That's an aggressive waste assumption — it says "you're losing 2 inches of diameter before you even start sawing." That's why Doyle gives the lowest numbers. It was designed for mid-19th-century sawmills with thicker kerf blades and more slab loss, and it stuck because it's easy to do in your head.

Scribner: John Scribner's original 1846 publication was not a formula — it was an enormous table listing exact board feet for every diameter/length combination you could imagine. That table was published in The Lumberman's Handbook and used by every New England sawmill for decades. The regression formula 0.79 × D² × L ÷ 12 that we use today was fit to Scribner's original table by the USDA Forest Service in the 1950s, and it matches the original values within 2% for diameters between 6 and 24 inches.

International 4-inch: This is the most modern and rigorous scale. It accounts for two things the others don't: first, a fixed 1-inch slab deduction (half of Doyle's, representing a more efficient modern head saw); second, taper — the fact that a real log is wider at the butt than at the top, and that extra volume at the wider end actually does produce more lumber. The "4-inch" in the name refers to the standard slab width. The full formula includes a taper adjustment by length: +0.5 inches of diameter gain per 8 feet of log length, which means longer logs yield more BF relative to their small-end diameter than shorter logs do.

MBF meaning in lumber — the sawmill pricing unit

If you spend any time around wholesale lumber, sawmills, or timber landowners, you will hear "MBF" used constantly. It stands for thousand board feet, and it's the default unit for almost every transaction in the wood products supply chain. A logger delivers 24 MBF of Red Oak to a mill. The mill quotes that oak at $1,100/MBF to a hardwood distributor. The distributor splits it up and sells it to cabinet shops at $1.20 per board foot — which is effectively $1,200/MBF. Everyone's on the same unit, everyone's comparing apples to apples.

But here's the catch: when someone quotes $900/MBF for Red Oak, you need to know two things. First, which scale that MBF was measured in. Second, what grade. A load of 12-inch × 12-foot Red Oak logs: Doyle scale gives 48 BF per log, so $900/MBF = $43.20 per log. Scribner scale gives about 114 BF per log, so if someone quotes Scribner-derived MBF at $900, that's actually $102.60 per log — way more per log but the same price per thousand BF. The "per thousand board feet" unit is meaningless if the board feet weren't calculated with the same scale.

Our calculator solves this by showing all three scales simultaneously, then letting you pick which one applies to your buyer and entering your price per MBF directly. The cost panel updates instantly. If you're selling logs, you can show a buyer their scale's BF number and your price, and there's no ambiguity. If you're buying logs, you can sanity-check the seller's scale against actual cubic volume and make sure you're not being over-billed.

How many board feet in a log — worked examples

Let's run a few concrete examples so you can see the scales in action. These use our calculator with live formula results so you can verify mentally:

Example 1 — 12 in × 12 ft (our default): Doyle = (12−4)²×12÷16 = 48 BF. Scribner ≈ 0.79×144×12÷12 = 113.8 BF. International 42 ≈ 0.82×144×12÷12 = 118.1 BF. Actual cubic volume = π×(12÷24)²×12 ≈ 9.42 ft³. So Doyle is ~5.1 BF/ft³, Scribner ~12.1 BF/ft³, International ~12.5 BF/ft³. The Doyle estimate is the most conservative because it subtracts that full 4-inch diameter deduction.

Example 2 — 16 in × 16 ft: Doyle = (16−4)²×16÷16 = 144 BF. Scribner ≈ 0.79×256×16÷12 ≈ 271 BF. International 42 ≈ 0.82×256×16÷12 ≈ 281 BF. Actual cubic volume ≈ 33.5 ft³. BF/ft³ ratios are now Doyle 4.3, Scribner 8.1, International 8.4. Notice that the BF-to-ft³ ratio changes with diameter and length — Doyle becomes relatively more conservative on larger logs.

Example 3 — 8 in × 8 ft (small softwood log): Doyle = (8−4)²×8÷16 = 8 BF. Scribner ≈ 0.79×64×8÷12 ≈ 33.8 BF. International 42 ≈ 0.82×64×8÷12 ≈ 35.0 BF. Actual cubic volume ≈ 2.79 ft³. Here the Doyle ratio is 2.9 BF/ft³ and Scribner is 12.1 — that's a massive discrepancy. This is exactly why Doyle is considered "conservative" — on small logs it penalizes you hard, because the 4-inch deduction is a larger fraction of the small diameter.

Example 4 — Bundle price calculation: Let's say you're buying 50 logs of Red Cedar, each 14-inch diameter × 12-foot length. Doyle BF per log = (14−4)²×12÷16 = 75 BF × 50 = 3,750 BF total = 3.75 MBF. At $650/MBF Red Cedar, that's 3.75 × $650 = $2,437.50. If the same logs were sold by Scribner, per log ≈ 139 BF × 50 = 6,950 BF = 6.95 MBF. At the same $650/MBF, that's $4,517.50 — almost double. And at International 42 it's about 7,250 BF total for $4,712.50. Same logs, same price per MBF, dramatically different invoices depending on the scale.

Sawmill board feet vs actual cubic feet — the conversion question

One number our calculator reports that most standalone log calculators skip is actual cubic feet of the log itself, calculated as a cylinder: π × r² × L, where r is half the small-end diameter in feet. Why does this matter? Because board feet is not a volume unit — it's a sawmill yield estimate. One board foot = 1/12 cubic foot only if you're talking about dressed lumber. A log's actual cubic feet is the physical volume of the cylinder of wood, including bark, defects, and waste.

Our "BF per cubic ft" panel shows the ratio of Doyle BF to actual cylinder volume. For a 12 in × 12 ft log, that ratio is about 5.1. For a 16 in × 16 ft log it's about 4.3. This ratio varies because Doyle's (D−4)² deduction is a fixed number, not a percentage — as logs get bigger, that 4 inches becomes a smaller relative deduction and the BF-per-ft³ ratio would actually go up if not for the length and diameter interplay. The actual BF-to-ft³ relationship is not linear, which is one more reason to use the calculator rather than a mental approximation.

Estimating log weight — a bonus conversion

If you're hauling logs, shipping them overseas, or estimating crane capacity, you need log weight, not just board feet. The simplest path is to take the Doyle BF (or whichever scale you're using), divide by 12 to get rough cubic feet, and multiply by species green density. Green densities (unseasoned) are about 1.25× the kiln-dried numbers on our lumber weight page. So a 12 in × 12 ft Doyle log = 48 BF ÷ 12 × 28 lb/ft³ × 1.25 ≈ 140 lb green SPF. That's rough but within 15% for most commercial species.

Or use the actual cubic feet from our calculator directly — that's even more accurate. The same log is 9.42 ft³ of actual cylinder volume (before sawmill waste), times green SPF density of about 35 lb/ft³ = ~330 lb including bark. Once you debark and saw it, you get down to roughly 48 BF × (1/12 ft³/BF) × 28 lb/ft³ ≈ 112 lb of dressed, kiln-dried lumber. This gives you three weight numbers for the same log: green with bark, post-sawmill dressed, and somewhere in between — which one matters depends on whether you're planning logging truck capacity, sawmill input volume, or finished-product shipping.

Why wood species doesn't affect board feet — and why the price gap matters

There's a common misconception that "oak logs scale to more BF than pine logs because oak is denser." They don't. A 12 in × 12 ft log is 48 Doyle BF whether it's SPF, Red Oak, or Black Walnut. Density, hardness, and species affect the value per board foot, not the volume estimate. The sawmill can actually saw a little more BF out of a straight-grained low-defect Black Walnut log vs a knotty Red Oak log of the same size — but that's a grade issue, not a scale issue. Grading is handled at the sawmill after sawing; scaling happens before.

This is why our calculator lets you enter a price per MBF directly rather than picking a species. Enter whatever your mill or buyer quotes — $400 for SPF, $900 for Red Oak, $1,600 for Black Walnut — and the cost panel does the math. Species pricing changes constantly with regional supply, export demand, kiln-dried vs green, and grade. What stays constant is the scale formula.

Using the calculator in practice — a day on the timber lot

Let's walk through a realistic scenario: you're a logger in the Appalachians and you just harvested 30 hardwood logs, mostly Red Oak, ranging from 12–18 inches diameter and 10–16 feet long. Your buyer is an Eastern sawmill that quotes Scribner scale at $950/MBF. How do you price the load?

First, you'd group logs by approximate diameter to run through the calculator efficiently — for this load let's say 10 small logs (12 in × 12 ft), 15 medium (14 in × 14 ft), 5 large (18 in × 16 ft). Run each group through Scribner scale: 12 in × 12 ft ≈ 114 BF each × 10 = 1,140 BF. 14 in × 14 ft ≈ 198 BF each × 15 = 2,970 BF. 18 in × 16 ft ≈ 471 BF each × 5 = 2,355 BF. Total ≈ 6,465 BF = 6.47 MBF. At $950/MBF, that's $6,146.50 gross. Now subtract your cost: felling, skidding, processing, trucking, site prep, and landowner payment. If your cost is $4,200, your margin is about $1,947 for the whole load. That's the real-world equation — BF is the input, MBF is the unit, and the calculator is how you run scenario numbers fast when you're on site.

Now imagine that same load if you'd quoted Doyle scale to the same buyer. Doyle BF for the same sizes is roughly half of Scribner, so you'd have ~3,000 Doyle BF = 3 MBF at $950/MBF = $2,850 — you'd have quoted yourself out of business before you even loaded the truck. And if someone tried to sell you a "12 MBF load" of hardwood, you'd instantly ask: which scale?

Edge cases and gotchas

Small logs under 8 inches. Doyle returns BF = 0 for anything under 4 inches diameter and gives very low estimates below 8 inches. Small-diameter poles and pulpwood are usually not scaled for lumber at all — they're sold by linear feet or by the cord.

Very long logs over 24 ft. Doyle doesn't account for taper, so long logs (over 16 ft) will be substantially underestimated by Doyle relative to their actual lumber yield. Use International 42 for these.

Butt logs (first log from the ground). The butt log of a tree is disproportionately wide at one end and narrow at the small end. Standard practice is to take the small-end diameter only and run the normal formula — but remember that the extra taper in the butt end means the International scale will yield a better (higher) BF estimate than Doyle.

Veneer logs. Veneer-quality Black Walnut or White Oak logs have value that dwarfs their lumber BF estimate — a single 18-inch veneer log can be worth $2,000–$5,000 regardless of scale. Our calculator is for saw lumber, not veneer, but the BF number is still a useful sanity check for volume.

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