🌳 Forestry Hub – Log Scaling

Scribner Log Scale Calculator: Decimal C Rounding, Log Grade Adjustment, Pacific Northwest Species Bark Deduction, and Multi-Log Tally

Built and reviewed by (MBA Finance) · Updated October 2026

The Scribner Decimal C rule powers federal timber sales across the Pacific Northwest. This calculator is the only free tool that implements the official USDA Decimal C rounding to the nearest ten board feet, adds per-log grade adjustment, includes 14 western species bark deduction factors, and runs a full tally session. Built for Oregon, Washington, Idaho, Montana, and California timber operations.

📐 Decimal C Rounding 🍋 Log Grade (1-4) 🌳 14 PNW Species 📝 Multi-Log Tally 📄 PDF Scale Ticket 📱 Mobile Field Tool
📐 Log Dimensions
inches

Measure at the small end, inside the bark. Round down to nearest inch per USDA Forest Service scaling standards.

feet

Common PNW log lengths: 8, 12, 16, 20, or 32 ft. Western long logs may run 20 to 40 ft.

🍋 Log Grade

Select the USDA log grade for price adjustment. Grade 2 (Standard) is default and applies no multiplier.

G1
Premium +15%
G2
Standard 1.0x
G3
Utility -20%
G4
Pulpwd -45%
🌳 Bark Deduction by Species (Optional)
in DOB

Select species first. DIB field updates with standard USDA Forest Products Lab bark deduction.

📈 Stumpage Value (Optional)
$/MBF

Enter your buyer’s quoted price per thousand board feet, Scribner scale. Applied to grade-adjusted BF.

📝 Log Tally Session  0 logs
#DIBLengthGradeSpeciesDec C BFRemove
Total Dec C:0 BFValue: –
📈 Scribner Raw vs Decimal C vs Doyle: Board Feet by Diameter (16-ft Log)

The Scribner Log Rule: How Federal Timber Sales Work in the Pacific Northwest and Why Decimal C Matters

If you have ever purchased timber through a USDA Forest Service sale in Oregon, Washington, Idaho, Montana, or Northern California, the volume and the price per unit was almost certainly expressed in Scribner Decimal C board feet. The Scribner rule was developed by D.C. Scribner in 1846, two decades after the Doyle rule, and it was designed from the beginning to be more accurate than its predecessor. Unlike Doyle, which uses a simple algebraic formula calibrated to single-kerf circular saw mills, the Scribner rule was originally constructed using diagrams of actual lumber cuts from logs of different diameters, giving it a grounding in observed sawmill practice that Doyle lacked.

The formula most commonly used today is the Scribner Decimal C approximation: BF = (0.79 times D squared, minus 2D, minus 4) times L divided by 16. This produces a raw board foot figure. What makes the Decimal C version distinct from the raw Scribner number is a rounding step: the result is rounded to the nearest 10 board feet. A log that calculates to 87.3 board feet raw Scribner becomes 90 board feet Scribner Decimal C. A log that calculates to 122.8 board feet becomes 120 board feet. This rounding was introduced to simplify field tabulation and to match the layout of official USDA Forest Service log scale tables, which are published in increments of 10 board feet. When a Forest Service contract says your timber will be scaled in Scribner Decimal C, the rounding is not optional. It is part of the standard. No other free online calculator available as of 2026 implements this rounding correctly.

The Scribner rule is meaningfully more accurate than the Doyle rule for small to mid-range diameter logs. At 10 inches inside bark, Scribner gives about 55 board feet against Doyle’s 36 for a 16-foot log. At 16 inches, Scribner gives 166 board feet against Doyle’s 144. As diameter increases beyond 20 to 24 inches, the two rules converge, and at very large diameters Doyle may slightly exceed Scribner. This convergence is one reason the historical boundary between Doyle and Scribner territory in American forestry aligns roughly with the boundary between eastern hardwood forests (where small-diameter logs are more common) and western conifer forests (where larger-diameter old-growth logs were historically the norm and where Scribner’s higher accuracy for those large logs was particularly valued).

Why Scribner Decimal C Is the Standard for USDA Forest Service Timber Sales

The USDA Forest Service manages approximately 193 million acres of national forests and grasslands across the United States. When the agency sells timber from these lands, the sale contract specifies the measurement standard. In the Pacific Northwest and Intermountain West, that standard is almost universally Scribner Decimal C. Log scalers certified through state forestry agencies or USDA contracts use Scribner Decimal C tables published in the Forest Service’s own Forest Products Measurement Handbook. These tables show board feet by diameter and length in the familiar ten-board-foot increments. When a private landowner in western Oregon sells timber adjacent to a national forest, they often accept Scribner pricing to match the market their mill buyers are already using for their Forest Service volume.

The certification of individual log scalers in Scribner states requires passing a practical examination on the Decimal C tables. Oregon, Washington, Idaho, and California each maintain their own certification programs through their state Departments of Forestry or Natural Resources. A certified scaler’s ticket carries legal weight in a timber contract dispute that a handwritten calculation does not.

Log Grades in the Scribner System: How Quality Adjusts the Price per MBF

Raw board feet are only part of the timber value equation. Log quality, expressed as log grade, significantly affects what a mill will pay per MBF for the same Scribner scale volume. The USDA Forest Service uses a four-grade system for softwood sawlogs that is also widely adopted in the private Pacific Northwest market. Grade 1 logs are the highest quality: they have clear faces, tight knots within specified limits, and are typically destined for high-value appearance lumber such as clear pine, shop grades, or export logs. These may command 10 to 15 percent premiums above standard prices. Grade 2 is the standard commercial sawlog grade, which is what most stumpage prices are quoted for. Grade 3 has more defects and may yield a higher proportion of utility or economy grades. Grade 4, sometimes called No. 4 or peeler core reject, has heavy defect and may only be marginal for sawing. This calculator applies an indicative price multiplier for each grade to help you estimate the realistic value of your log mix before a formal appraisal.

How Each Input in the Scribner Log Scale Calculator Works Step by Step

This calculator implements the Scribner Decimal C formula with four features that no other free online tool offers simultaneously: the correct Decimal C rounding, per-log grade selection with price adjustment, 14 Pacific Northwest species bark deduction factors, and a running multi-log tally session with PDF export.

Diameter inside bark: The Scribner formula requires the small-end diameter inside bark, rounded down to the nearest inch, exactly as with the Doyle rule. Measurement is taken at the small (top) end of the log on a fresh cut face. For standing timber, outside-bark diameter from a dendrometer, diameter tape, or Biltmore stick is converted to inside bark using the species-specific bark factor. USDA Forest Service log scalers are trained to measure DIB directly on cut logs or to apply standard bark factors for the species in their area.

Scribner Decimal C rounding: After the formula calculates the raw board foot figure, this calculator rounds to the nearest 10, producing the Decimal C value. Both numbers are shown in the results so you can see exactly how the rounding affects your specific log. For a 14-inch log 16 feet long, raw Scribner is 122.8 board feet, and Decimal C rounds to 120. For a 16-inch log, raw is 166.2 and Decimal C rounds to 170. For very small logs at 6 inches, both round to 10 board feet (or 0 in some published tables). The Decimal C value is what you will see on a USDA Forest Service scale ticket and what should match any contract based on this standard.

Log grade selection: The four-button grade selector lets you mark each log as Grade 1 Premium, Grade 2 Standard, Grade 3 Utility, or No. 4 Pulpwood Grade. The grade adjustment multiplier is applied to the Decimal C board feet when calculating stumpage value, not to the board foot volume itself. This distinction matters: your scale ticket records volume in board feet regardless of grade, but the price per MBF you receive varies by grade. A 170 BF Grade 1 log at $480 per MBF returns $81.60. The same 170 BF log at Grade 3 and $480 per MBF base would return $65.28 after the 80% quality adjustment. The grade multipliers in this calculator (1.15, 1.00, 0.80, 0.55) are indicative values based on typical PNW market differentials and should be verified against your specific buyer’s grading price schedule.

Pacific Northwest bark deduction: Fourteen western US species are included with their standard bark deduction factors from USDA Forest Products Laboratory reference data. Western Red Cedar has the thickest bark of the listed species at 0.82, meaning a 16-inch outside-bark measurement converts to approximately 13.1 inches inside bark. Douglas Fir at 0.87 is the most commonly scaled PNW species. Red Alder at 0.93 has the thinnest bark in the list. Select species first, then enter the outside-bark diameter to automatically populate the DIB field.

Three Real Scribner Log Scale Calculations from Pacific Northwest Timber Markets

Oregon Logger Delivering a Douglas Fir Load to a Willamette Valley Mill

A timber harvester in Lane County, Oregon delivers a truckload of Douglas fir logs to a sawmill in the Willamette Valley that buys on Scribner Decimal C scale. The load has 8 logs: four at 16-inch DIB and 16 feet long, and four at 12-inch DIB and 16 feet long. The mill’s posted price is $415 per MBF Scribner Decimal C for Grade 2 Douglas fir sawtimber. He measured these logs outside bark at 18 inches and 14 inches respectively, then applied the Douglas fir bark factor of 0.87 to arrive at the inside-bark diameters.

16-inch logs: raw Scribner = (0.79 x 256 minus 32 minus 4) x 1 = 166.2 BF, rounds to 170 BF Dec C. Four logs = 680 BF. 12-inch logs: raw = (0.79 x 144 minus 24 minus 4) x 1 = 85.8 BF, rounds to 90 BF Dec C. Four logs = 360 BF. Total tally: 1,040 BF Scribner Decimal C. Value: 1.040 MBF x $415 = $431.60.

Result: Scale ticket should read 1,040 BF Dec C and $431.60 at $415/MBF Grade 2. If the same logs were scaled Doyle, the total would be about 800 BF, yielding $332 at the same dollar price per MBF. The Scribner price in this example is meaningfully higher, reflecting its more accurate volume measurement.

Washington Landowner Navigating a USDA Forest Service Timber Sale Adjacent to Olympic National Forest

A private landowner in Grays Harbor County, Washington has 20 acres of mixed second-growth timber adjacent to the Olympic National Forest. A forestry consultant performs a timber cruise and estimates the merchantable volume. The dominant species is Western Hemlock with some Sitka Spruce. Average log: 14-inch DIB, 20 feet long, mixed Grade 2 and Grade 3. Approximately 60 logs estimated in the merchantable tally. The local market is paying $380 per MBF Scribner Grade 2 and about $305 per MBF Grade 3 for western hemlock, driven partly by export demand.

For a 14-inch x 20-foot Hemlock log: raw Scribner = (0.79 x 196 minus 28 minus 4) x 20/16 = 122.8 x 1.25 = 153.5 BF, rounds to 150 BF Dec C. If 40 logs are Grade 2 and 20 are Grade 3: Grade 2 total = 40 x 150 = 6,000 BF x 1.0 = 6,000 adj BF. Grade 3 total = 20 x 150 = 3,000 BF x 0.80 = 2,400 adj BF. Value: (6,000/1,000 x $380) + (2,400/1,000 x $305) = $2,280 + $732 = $3,012.

Result: Estimated stumpage: $3,012 for the mixed-grade tally. A consultant advises competitive bidding, as western hemlock values can vary 15 to 25 percent between buyers depending on their grade program and export allocations. Submitting sealed bids to three or four regional buyers is the standard recommendation for any sale of this size.

Idaho Forestry Consultant Scaling Western Larch from a Private Ranch Sale in Clearwater County

A forestry consultant in Clearwater County, Idaho scales 35 Western Larch logs from a private ranch timber harvest. Larch logs average 18-inch DIB at 16 feet. The outside-bark measurement was 21 inches, converted using the Western Larch bark factor of 0.85 to 17.9 inches inside bark, which rounds down to 17 inches DIB per scaling convention. Idaho buyers in the Clearwater drainage typically pay $360 to $450 per MBF Scribner Dec C for quality larch, which is prized for its density, rot resistance, and appearance characteristics.

17-inch DIB x 16-foot log: raw Scribner = (0.79 x 289 minus 34 minus 4) x 1 = (228.31 minus 38) x 1 = 190.3 BF, rounds to 190 BF Dec C. 35 logs x 190 BF = 6,650 BF = 6.65 MBF. At Grade 2 and $405/MBF: 6.65 MBF x $405 = $2,693.25. At Grade 1 premium for select larch: 6.65 MBF x $465 = $3,092.25. The grade matters: if the consultant can establish Grade 1 quality on these larch logs, the additional value is nearly $400 on this single tally.

Result: 6,650 BF Dec C total. Value range: $2,693 (Grade 2) to $3,092 (Grade 1) depending on log quality and buyer grading. Western Larch bark factor of 0.85 reduced effective diameter from 21-inch measurement to 17-inch scale, a reduction of 4 inches that significantly affects the scale ticket vs a naive diameter entry.

Three Expert Tips for Maximizing Accuracy on Scribner Scale Timber Sales

Understand That Decimal C Is Not the Same as Raw Scribner

Many online tools and even some buyers quote raw Scribner without applying the Decimal C rounding. For large logs, the difference is small. For smaller logs where rounding constitutes a larger percentage of the total, the gap is meaningful. A 10-inch log at 16 feet calculates to 55.0 raw Scribner, which rounds to 60 Decimal C. That is nearly 9 percent more volume on the scale ticket than the raw number would suggest. Over a full tally of 50 small-diameter logs, this rounding effect can change your stumpage check by a noticeable amount. Always verify that your buyer’s scale ticket specifies Decimal C and applies the rounding correctly. If a ticket shows values that are not multiples of ten, it is either showing raw Scribner (which should be specified in the contract) or contains a computational error.

Apply Species-Specific Bark Deduction Before Entering Diameter

Using outside-bark diameter directly in the Scribner formula without a bark deduction overstates board foot volume by 10 to 20 percent depending on species. In federal timber sales, the USDA Forest Service requires certified scalers to measure inside bark or to apply approved bark deduction factors. Western Red Cedar with its extremely thick, fibrous bark requires the largest deduction in the Pacific Northwest: at 0.82, a 20-inch outside-bark Cedar log is effectively 16.4 inches inside bark, which rounds to 16 inches for scaling. Without the deduction, you would enter 20 inches and calculate a significantly higher board foot volume that does not reflect actual lumber yield. The bark deduction for the species you select is applied automatically in this calculator when you enter an outside-bark diameter in the DOB conversion field.

Know When to Request a Certified Scaler Recheck in Oregon, Washington, and Idaho

All three major Scribner states in the Pacific Northwest maintain legal processes for disputing a log scale. In Oregon, the Oregon Department of Forestry oversees log scaling certification. In Washington, the Washington Department of Natural Resources administers the log scaling program. In Idaho, the Idaho Department of Lands manages timber measurement programs. If you receive a scale ticket that you believe understates your volume, you generally have the right to request a recheck within a specified window (often 24 to 48 hours in active scaling programs). A recheck requires the presence of a certified scaler and, in some programs, a nominal fee. The investment is worth it on large loads or where a systematic scaling error may have affected multiple tickets from the same buyer. Calculating your expected scale using this tool before delivery lets you flag suspicious tickets immediately.

Quick Reference: Scribner Decimal C Scale Table for Pacific Northwest Sawlogs

Board feet Scribner Decimal C per log. Raw Scribner values computed using BF = (0.79D squared minus 2D minus 4) times L/16, then rounded to nearest 10 board feet. Based on USDA Forest Service scaling standards and the Scribner Decimal C tables in the Forest Products Measurement Handbook. DIB = diameter inside bark at small end, rounded to nearest inch.

DIB (in)8-ft Dec C12-ft Dec C16-ft Dec C20-ft Dec C32-ft Dec C
6″010101020
8″1020304060
10″30406070110
12″406090110170
14″6090120150240
16″80130170210330
18″110160220270430
20″140200270340540
24″200300400500800

Frequently Asked Questions About the Scribner Log Rule in the Pacific Northwest

What is Scribner Decimal C and how does it differ from regular Scribner?
Scribner Decimal C is the version of the Scribner log rule in which the calculated board foot value is rounded to the nearest 10 board feet. The word Decimal in the name refers to the rounding to tens (not to a decimal point). Unrounded Scribner gives results like 122.8 or 166.2 board feet. Decimal C rounds those to 120 and 170 respectively. This rounding was adopted by the USDA Forest Service to simplify field tabulation and to match the format of official published log scale tables, which have always been arranged in increments of 10 board feet. When a Forest Service contract or a Pacific Northwest mill purchase order specifies Scribner Decimal C, the rounding is mandatory and built into the standard. The raw unrounded Scribner formula may be used for educational comparison, but Decimal C is the contract standard for virtually all commercial timber transactions in Oregon, Washington, Idaho, Montana, and Northern California.
Which US states use the Scribner log rule and which use Doyle?
The Scribner Decimal C rule dominates in the Pacific Northwest and Intermountain West: Oregon, Washington, Idaho, Montana, Wyoming, Northern California, Nevada, and Alaska. The Doyle rule dominates in the eastern and southern United States: Georgia, Tennessee, Virginia, West Virginia, North Carolina, South Carolina, Kentucky, Alabama, Mississippi, Arkansas, Missouri, and Indiana. The Midwest and Northeast are a mixed zone where the International 1/4-inch rule has historically been preferred for timber appraisals, though Doyle is still used in many buyer contracts. The boundary is not perfectly clean: individual mills in any state may specify whichever rule they prefer in their purchase contracts, and some buyers use different rules for different species. If you are uncertain which rule applies to your transaction, the rule should be explicitly stated in the purchase order or stumpage agreement.
How are logs graded in the Pacific Northwest softwood market?
Pacific Northwest softwood log grades are typically based on visible surface characteristics including knot size, frequency, and tightness, the presence of sweep or crook, checks, rot, and other defects. The USDA Forest Service uses a four-grade system for softwood sawlogs: Grade 1 for premium clear or near-clear logs, Grade 2 for standard commercial sawlogs with limited defect, Grade 3 for sawlogs with more significant defect, and No. 4 for the lowest grade that justifies sawing at all. Private mills in the Pacific Northwest have their own grading specifications, sometimes more detailed, that determine the price differential between grades. Export log buyers have additional grades related to face quality and diameter requirements for specific overseas markets. The grade multipliers in this calculator (1.15 for Grade 1, 1.00 for Grade 2, 0.80 for Grade 3, and 0.55 for No. 4) are approximations based on typical PNW price differentials and should not be used as actual contract prices without verification against your specific buyer’s grade schedule.
Why is Scribner more accurate than Doyle for western softwoods?
The Scribner rule was designed using diagrams of actual lumber cuts from logs of different diameters, giving it a basis in observed sawmill practice. Its formula (0.79D squared minus 2D minus 4) was fit to those observations and, as a result, tracks actual lumber yield more closely than the Doyle formula across most of the commercial diameter range for western conifers. The 4-inch fixed deduction in the Doyle formula was calibrated to mid-1800s mill technology with thick kerf saws, which severely overstates waste on modern thin-kerf band saw operations and, as previously noted, penalizes small-diameter logs disproportionately. Scribner is not perfectly accurate either, particularly for logs at the extremes of the diameter range, but it is consistently closer to actual mill recovery across the 10 to 24 inch range where most Pacific Northwest sawlogs fall. The International 1/4-inch rule is generally considered the most accurate of the three, but Scribner Decimal C remains the accepted commercial and regulatory standard in the Pacific Northwest because it has been in institutional use for well over a century and changing industry-wide standards requires consensus that has not materialized.
What do log scalers actually measure to produce a Scribner scale ticket?
A certified log scaler measuring a truckload of logs at a Pacific Northwest mill yard typically works through the following process: the log is identified (species, measured length rounded to the nearest standard foot, typically with a 0.3-foot trim allowance), the diameter at the small end is measured inside the bark using a flexible diameter tape or diameter stick, that measurement is rounded down to the nearest inch, the scaler looks up the resulting diameter and length combination in the official Scribner Decimal C table (or applies the formula), records the board feet for that log, and moves to the next. The scaler also records any defect deductions for visible rot, shake, crook, or other defects that reduce the usable log volume. The final scale ticket shows individual log entries and a total for the load. On modern operations, portable electronic scaling devices running certified scaling software speed up this process while maintaining the same fundamental measurements and table lookups.
How does taper affect Scribner scale and how is it handled in the field?
All major US log rules, including Scribner, Doyle, and International, measure only the small-end diameter and assume a cylindrical log shape for the formula. Real logs taper from large end to small end, so they contain more wood than a cylinder of the small-end diameter and length would suggest. The USDA Forest Service handles taper through a combination of log length standardization (shorter log lengths reduce the effect of taper on any single measurement) and occasionally through the use of a form class adjustment for standing timber volume estimates. For individual log scaling in the field, taper is not separately measured or entered. The small-end diameter is the controlling measurement, and any additional volume due to taper represents overage that the mill recovers. This is one reason actual mill recovery consistently exceeds Scribner scale even though Scribner is more accurate than Doyle: both rules ignore taper, and real taper always adds wood to the large-end portion of the log beyond what the formula predicts.
What is the minimum merchantable log diameter for Scribner scale in the Pacific Northwest?
The Scribner formula technically produces a positive value for any log with a diameter above approximately 5.6 inches inside bark, the point where (0.79D squared minus 2D minus 4) equals zero. In practice, most Pacific Northwest mills have minimum diameter requirements for scale logs that are considerably higher than the mathematical minimum. A common threshold is 6 inches inside bark at the small end for pulpwood or chip-and-saw grade material, and 8 inches inside bark for sawlog grade. Some mills require 10 or 12 inches inside bark for their primary saw lines. These minimums reflect equipment design and economic viability, not formula limits. Logs below the mill’s minimum may be merchantable as pulpwood (sold by the ton or cord) or as biomass (chipped for energy), but they will not receive a Scribner sawlog scale ticket regardless of what the formula would produce.
How do I convert Scribner prices to compare with Doyle prices from eastern buyers?
The conversion factor between Scribner and Doyle varies significantly with log diameter, which makes a single universal ratio misleading. For the most common commercial log diameters in the 10 to 20 inch range, Scribner scale is typically 25 to 55 percent higher than Doyle scale on the same physical log. A price quote of $300 per MBF Doyle and $240 per MBF Scribner may actually represent the same economic value for a 12-inch log, because the Scribner volume estimate for that log is about 34 percent higher than the Doyle estimate. To compare bids that use different rules: calculate both Scribner and Doyle board feet for your average log size using this calculator and the Doyle calculator, find the ratio, then adjust the dollar amounts accordingly. For example, if your 14-inch logs give 122 BF Scribner and 100 BF Doyle (ratio 1.22), a $350 Scribner offer is equivalent to $350 divided by 1.22 = $287 Doyle, making a $320 Doyle offer from a different buyer the better deal for those logs.
Does the USDA Forest Service use Scribner for all its timber sales in the West?
Scribner Decimal C is the dominant measurement standard for USDA Forest Service sawtimber sales in the western United States, and it is specified in the agency’s national forest timber sale contracts for softwood sawlogs in the Pacific Northwest, Intermountain West, and Southwest regions. However, the Forest Service also sells timber in the eastern United States, where contracts for National Forests in the Appalachians, the South, and the Midwest may use Doyle or International depending on the regional market standard. For special products such as poles, posts, or piling, different measurement systems apply. Pulpwood and biomass from Forest Service sales are measured by weight or cord rather than board feet. The contracting officer’s terms and conditions for each specific sale will state the applicable measurement rule, and the agency publishes its current timber measurement standards through the USDA Forest Service Forest Management technical program, available at fs.usda.gov/forestmanagement.
What Western Red Cedar bark factors should I use for Scribner scaling?
Western Red Cedar (Thuja plicata) has the thickest bark of any major commercial species in the Pacific Northwest. The standard bark deduction factor for Western Red Cedar recognized in USDA Forest Products Laboratory reference data is 0.82, meaning the inside-bark diameter is approximately 82 percent of the outside-bark diameter. On a 20-inch outside-bark Cedar, this gives 16.4 inches inside bark, rounded to 16 inches for scaling. The thick, fibrous bark of Cedar is one reason why Cedar stumpage prices, when quoted per MBF Scribner, often appear lower than comparable Douglas Fir or Hemlock prices: the buyer is aware that a larger fraction of the gross log volume is bark rather than merchantable wood. When comparing Cedar stumpage prices across buyers, always confirm whether the quoted price is based on inside-bark or outside-bark scaling, and apply the bark deduction consistently. The 0.82 factor in this calculator applies to mature second-growth and old-growth Cedar; young plantation Cedar may have slightly thinner bark and a higher deduction factor.
How do long logs (over 20 feet) affect Scribner scale in the Pacific Northwest?
The Pacific Northwest has a tradition of long-log harvesting, particularly for large-diameter conifers like Douglas Fir, Sitka Spruce, and Western Red Cedar. Logs of 32, 40, or even longer are bucked in some operations depending on the mill’s log deck capacity and equipment. The Scribner formula scales linearly with length: a 32-foot log of a given diameter will have exactly twice the board feet of a 16-foot log of the same diameter. This linearity simplifies calculation but does not account for the additional taper on longer logs (the large end of a 32-foot log is proportionally further from the small end and has more wood than the formula suggests). Many mills have equipment limits that restrict maximum log length, and some pay premiums for specific long log dimensions prized for producing wide or long lumber. The length conversion factor L/16 in the Scribner formula works for any length: a 32-foot log uses L/16 = 2.0 as the multiplier, and a 24-foot log uses L/16 = 1.5.
What is the role of defect deductions in Scribner log scaling?
Defect deductions reduce the scaled board foot volume of a log to account for visible deterioration that reduces the usable lumber yield. Common defects that trigger deductions in Scribner scaling include: ring or shake (separation along growth rings, which produces boards that fall apart), red or white rot (fungal wood decay), crook or sweep (curvature that requires the mill to rotate the log and lose more wood on the curved side), fork or knot clusters that would reduce yield below the formula prediction, and charred wood from fire damage. Defect deductions are expressed as a percentage of the calculated Scribner volume and are applied by the certified scaler based on visible inspection. A log with 20 percent defect from a rot column would have its Scribner board feet reduced by 20 percent on the scale ticket. This calculator does not apply defect deductions because they require visual inspection in the field by a trained scaler; it calculates the theoretical sound-log volume only.
How should I prepare logs for delivery to a Scribner mill to maximize my scale?
Maximizing Scribner scale starts in the woods, not at the mill yard. Accurate bucking to standard lengths with proper trim allowance ensures the full log length is credited. Bucking to minimize sweep and crook keeps defect deductions low. Clean cuts on the end face facilitate accurate diameter measurement. Keeping bark intact until scaling (removing bark before scaling would eliminate the need for bark deduction but also remove the actual logs from their protective sheath) protects the wood from staining and checking that could cause defect deductions. For species where bark is very thick (Cedar, older Ponderosa Pine), some loggers and buyers agree to scale on peeled logs, eliminating the bark deduction question. On high-value loads, some landowners arrange for independent certified scale to confirm the mill’s ticket before signing. The state forestry agency in Oregon, Washington, or Idaho can provide referrals to independent certified log scalers.
What timber prices should I expect for Scribner-scale logs in Oregon and Washington in 2026?
Timber prices in Oregon and Washington fluctuate significantly with lumber markets, export demand, mill capacity, and broader economic conditions. As a general frame of reference for the Pacific Northwest in recent years, Douglas Fir sawtimber has traded in the range of $300 to $550 per MBF Scribner Decimal C for Grade 2 material depending on diameter, quality, and local mill competition. Western Hemlock has generally been lower, at $200 to $400 per MBF, reflecting its lower value in domestic lumber markets though it commands strong export premiums in some markets. Western Red Cedar is prized for its natural decay resistance and has traded at $400 to $700 per MBF or more for quality material. For current prices, the Oregon Department of Forestry publishes quarterly stumpage price reports, and the Washington Department of Natural Resources similarly publishes timber price information. The USDA Forest Service publishes prices realized in Forest Service timber sales through their ATIS timber sale information system. These are starting points; your actual price depends on competitive bidding in your specific location.
Can I use the Scribner formula for hardwoods in the Pacific Northwest like Red Alder?
Technically yes, the Scribner formula can be applied to any species, and in Pacific Northwest markets where Red Alder and Bigleaf Maple are sold as sawlogs, buyers may use Scribner scale for pricing consistency with the dominant regional standard. Red Alder is the most commercially significant hardwood in the Pacific Northwest and is an important furniture and cabinet wood. Bigleaf Maple is harvested at smaller volumes for high-value figured wood. Both are included in this calculator with their species-specific bark deduction factors (Alder 0.93, Bigleaf Maple 0.92). In practice, some hardwood buyers in the Pacific Northwest use custom pricing that references either Scribner scale or cubic foot volume rather than board feet, particularly for smaller-diameter material. Always verify the measurement basis with your buyer before delivering hardwood logs, as the rules for softwoods and hardwoods may differ even within the same state or region.
Where can I find the official USDA Forest Service Scribner Decimal C log scale tables?
The official Scribner Decimal C log scale tables used by USDA Forest Service certified scalers are published in the Forest Service’s Forest Products Measurement Handbook, available through the agency’s Forest Management program. These tables show board feet by diameter and length in the Decimal C format (values in multiples of 10) and cover the full range of commercial log sizes encountered in Pacific Northwest timber sales. The USDA Forest Products Laboratory in Madison, Wisconsin publishes research on log measurement accuracy and log rule comparison. State forestry agencies in Oregon (Oregon Department of Forestry), Washington (Washington DNR), and Idaho (Idaho Department of Lands) also publish log scaling references and lists of certified log scalers. For training materials and examination preparation, the Pacific Northwest Log Scalers Association and similar professional organizations provide resources for individuals seeking log scaling certification. This calculator serves as a field check tool; it does not replace certified scaling for commercial or contractual purposes.

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Lumber cost, board foot, and wood project planning tools for woodworkers and home builders.

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This Scribner Log Scale Calculator implements the Scribner Decimal C approximation formula BF = (0.79 times D squared minus 2D minus 4) times L/16 as referenced in USDA Forest Service measurement standards. Decimal C values are rounded to the nearest 10 board feet per USDA convention. Log grade adjustment multipliers (Grade 1: 1.15x, Grade 2: 1.00x, Grade 3: 0.80x, No. 4: 0.55x) are indicative values based on typical Pacific Northwest price differentials and do not constitute a timber appraisal or guarantee any specific price. Species bark deduction factors are based on USDA Forest Products Laboratory reference data and represent averages that may vary by site, tree age, and local conditions. All results are estimates for planning and educational purposes. Commercial timber sales require certified log scalers and legally binding contracts. USCalculators.com is not affiliated with the USDA Forest Service, any state forestry agency, or any timber company. Authority references: USDA Forest Service Forest Products Measurement; USDA Forest Products Laboratory; Oregon Department of Forestry; Washington Department of Natural Resources. Tool last updated August 2026.