🌳 Forestry Hub – Timber Cruising

Standing Timber Volume Calculator: Girard Form Class, Per-Log Section Breakdown, Multi-Tree Stand Cruise Tally, and Stumpage Valuation for US Timber Markets

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

The only free standing timber volume tool that applies the Girard Form Class method with an adjustable taper per log section, shows every 16-foot section’s estimated board feet under all three US log rules, and builds a full stand cruise tally you can export as a PDF cruise sheet. Built for landowners, consulting foresters, and timber buyers across all US forest types.

🌳 Girard Form Class 📈 Per-Section Breakdown 📝 Multi-Tree Stand Tally 🍋 17 Species Bark Factor 📄 PDF Cruise Sheet 📱 Field-Ready Mobile
🌳 Tree Measurements
inches

Measure at 4.5 feet above ground on the uphill side. Standard US timber cruising measurement. Outside bark.

logs

Count from stump to merchantable top (typically 4-inch DIB minimum). A 60-ft merchantable height = about 3.5 logs; use 3 or 4.

in/log

How much DIB decreases per 16-ft section. Average US commercial timber: 2.0 in. Managed softwood: 1.0-1.5 in. Open-grown hardwood: 2.5-3.0 in.

📈 Girard Form Class: 68

Form class = (DIB at top of first log) / (DBH inside bark) x 100. Sets the first log’s small-end diameter. Drag slider to adjust.

60 82

FC 60-65: poor/average hardwood. FC 68-72: good eastern hardwood. FC 75-82: managed pine or high-quality softwood.

$/MBF

Enter buyer’s quoted price per thousand board feet (Doyle) to calculate estimated tree and stand value.

🪓 Per-Log Section Breakdown: All Three US Rules Side-by-Side
SectionSm-End DIBDoyle BFScribner BFInt’l 1/4″ BF
Enter tree measurements above and click Calculate to see per-log breakdown.
📝 Stand Cruise Tally  0 trees
#DBHLogsFCSpeciesDoyle BFRemove
Stand Total:0 BFValue: –
📈 Doyle vs International 1/4″ Board Feet by DBH Class (4 logs max, current form class and taper settings)

Standing Timber Volume Estimation: Why the Girard Form Class Method Is the Standard for US Timber Cruising

When a consulting forester walks a woodlot in Ohio or a timber buyer scouts a stand of pines in Georgia, they do not cut down a tree and measure each log to determine its value. They measure the tree where they stand: a diameter tape wrapped around the trunk at exactly 4.5 feet above ground (called DBH, diameter at breast height), a clinometer reading for total tree height, and a trained eye for merchantable bole length and quality. From those three inputs, plus knowledge of the species and site, they estimate the board foot volume of the standing tree well enough to negotiate a contract, produce an appraisal, or complete a timber cruise for sale planning.

The method that converts a standing tree’s outside-bark DBH into an estimated board foot volume in any of the three major US log rules is the Girard Form Class method, developed by Clement Girard in the early 20th century while working at the USDA Forest Products Laboratory in Madison, Wisconsin. Girard’s key insight was that trees of the same DBH can vary dramatically in how much useful lumber they contain, depending on how cylindrical or tapered the merchantable bole is. A tall, straight second-growth pine with a full, columnar trunk contains far more lumber per inch of DBH than a short, open-grown hardwood with a heavily tapered, branch-laden bole of the same diameter. Form class quantifies this difference.

The Girard Form Class is defined as the ratio of the inside-bark diameter at the top of the first 16-foot log (approximately 17 feet above ground, above a 1-foot stump) to the inside-bark DBH, expressed as a percentage. A form class of 68 means the first log’s top diameter is 68 percent of the inside-bark DBH. For a 16-inch DBH White Oak with a bark factor of 0.90 (DBH inside bark = 14.4 inches), form class 68 gives a first log top diameter of 14.4 times 0.68 = 9.8 inches inside bark. That 9.8-inch small end is the input to the Doyle formula for the first log. Successive logs lose additional diameter due to taper, and the board feet of each section is computed separately and summed for the tree total.

This calculator implements the full Girard Form Class workflow with adjustable taper per section, 17 species bark deduction factors, all three US log rules calculated simultaneously for each log section, and a multi-tree stand tally for use as a field cruise worksheet. It is the only free online standing timber volume tool that shows a visual per-section breakdown, which is what professional foresters actually compute when estimating individual tree values.

How DBH, Form Class, and Taper Interact to Determine Standing Tree Volume

Three inputs control everything: DBH, form class, and taper per section. Getting them right for your specific stand makes the difference between a rough estimate and a figure close enough to base a contract on.

DBH is the most straightforward: measure at 4.5 feet above ground on the uphill side of the tree using a diameter tape (the tape wraps the circumference and reads out diameter directly) or a Biltmore stick held at arm’s length. Round to the nearest half inch for the cruise; most volume tables and formulas are not sensitive to differences of a tenth of an inch in DBH. The outside-bark measurement is the field standard; bark deduction to inside bark is applied afterward using species-specific factors.

Form class is estimated rather than measured for each tree in a typical cruise. Foresters use one of three approaches: measuring a representative sample of trees with a dendrometer (an optical instrument that can measure diameter at any height from a distance), applying regional default form class values for the species and site quality from USDA published tables, or using a form class table that correlates DBH to form class for specific species. For most eastern hardwood stands, form class 65 to 70 is a reasonable default. Well-stocked, second-growth Appalachian hardwoods on good sites tend to fall in the 65 to 70 range. Managed southern yellow pine plantations may run 75 to 82. Open-grown farm woodlot hardwoods may be 60 to 65. Adjusting the form class slider in this calculator shows you immediately how sensitive total tree volume is to this assumption.

Taper per 16-foot log is the reduction in inside-bark diameter from one log section to the next. Two inches per 16 feet is the commonly cited average for eastern US commercial timber. But stands with unusually straight, tall trees on good sites may taper at only 1 to 1.5 inches per section, while open-grown trees or trees on marginal sites may taper at 2.5 to 3 inches. The per-section breakdown table in this calculator shows exactly how taper depletes each successive log’s diameter and board foot yield, making visible a phenomenon that is often invisible in simple lookup-table-based volume estimates.

Why Volume Tables Exist and When You Should Use This Calculator Instead

The USDA Forest Service and most state forestry agencies publish standard timber cruise volume tables: lookup tables indexed by DBH and number of 16-foot logs (or merchantable height in feet) that give board feet per tree under a specified log rule and form class. These tables are pre-computed versions of exactly the calculation this tool performs interactively. The advantage of the tables is speed in the field: a forester can look up a 16-inch DBH tree with 3 logs in the Doyle table and read off the volume without doing any arithmetic. The disadvantage is inflexibility: the tables assume a fixed form class (often 68 or 70) and a fixed taper, which may not match your specific stand conditions.

This calculator is most valuable when you want to: understand how sensitive your volume estimate is to form class assumptions (by dragging the slider and watching the results change), explore different taper scenarios for a specific stand, compare all three log rules simultaneously for each tree you measure, or build a custom cruise tally for a small woodlot where the standard tables may not match your stand’s characteristics. For large commercial cruises where speed matters and the standard form class is appropriate for the stand, published USDA tables from the Forest Products Laboratory or state forestry agencies remain the fast standard tool.

How to Use Each Input in the Standing Timber Volume Calculator

The calculator needs four measurements or estimates: DBH, species for bark deduction, number of merchantable 16-foot log sections, and the Girard Form Class. Taper per log and stumpage price are optional refinements.

DBH outside bark: The measurement you take in the field with a diameter tape at 4.5 feet above ground. This is outside the bark. The species bark deduction converts it to inside-bark DBH, which is then used in the form class calculation. If you measure multiple trees across a stand, you can enter each one separately and add it to the stand tally, or you can enter the average DBH for a diameter class and multiply by tree count in the tally to get a class-total estimate.

Species and bark deduction: Select the tree species to apply a standard bark deduction factor. This converts outside-bark DBH to an inside-bark estimate for the form class calculation. If you have already measured inside-bark DBH directly (by pressing a diameter stick into a fresh cut on a sample tree), select “No deduction.” Red Oak and Hickory have the thickest bark of the eastern hardwood species listed, with factors of 0.88. Red Maple has the thinnest eastern hardwood bark at 0.93. Western Red Cedar has the thickest bark overall at 0.82.

Number of 16-foot logs: Count the merchantable log sections from a 1-foot stump height to the point where the stem becomes too small, crooked, or defective to produce merchantable lumber. A tree with 48 feet of straight, clean stem above the stump contains 3 full 16-foot logs. A tree with 64 feet of merchantable height contains 4 logs. Most second-growth eastern hardwoods in the 14 to 20 inch DBH range yield 2 to 4 merchantable logs. The calculator stops computing log sections when the estimated diameter drops below 4 inches inside bark, since Doyle scale gives zero for logs 4 inches and under.

Girard Form Class slider: Drag the slider from 60 (very tapered tree) to 82 (near-cylindrical) to set the form class. The display updates the first log’s small-end DIB in real time as you drag. For most eastern hardwood cruises, 65 to 70 is appropriate. For managed pine plantations in the South, 75 to 80 is reasonable. Use published form class data from your state forestry agency when available for the best accuracy.

Taper per 16-ft section: Default is 2.0 inches per log, representing average US commercial timber taper. Adjust down to 1.0 for dense stands with good stem form, or up to 3.0 for open-grown trees or difficult sites. Each 0.5-inch change in taper per log significantly affects upper-log volumes, especially for trees with 3 or more logs.

Three Real Standing Timber Volume Estimates from US Forest Types

Appalachian Hardwood Stand Cruise in Fayette County, West Virginia

A consulting forester conducting a pre-sale timber cruise in a mixed Appalachian hardwood stand in Fayette County, West Virginia tallies a 16-inch DBH White Oak. He estimates 3 merchantable 16-foot logs based on the visible stem height and quality. The stand is well-stocked second-growth on a north-facing slope, and he uses a form class of 68 (average for well-managed Appalachian hardwoods). Bark factor for White Oak: 0.90. DBH inside bark: 16 x 0.90 = 14.4 inches. First log small-end DIB: 14.4 x 0.68 = 9.8 inches. Using 2-inch taper per log: second log DIB = 7.8 inches, third log DIB = 5.8 inches.

Doyle BF by section: Log 1: ((9.8-4)^2 x 16)/16 = 33.6 BF. Log 2: ((7.8-4)^2 x 16)/16 = 14.4 BF. Log 3: ((5.8-4)^2 x 16)/16 = 3.2 BF. Total: 51.2 BF Doyle. At $280/MBF: $14.34 per tree. International 1/4-inch total: 100.9 BF. The forester counts 120 similar White Oak trees across the 40-acre stand, giving an estimated 6,144 BF Doyle or approximately $1,720 stumpage at current market rates before accounting for species and size variation within the tally.

Result: 51.2 BF Doyle per tree, 100.9 BF International. The International volume is nearly twice the Doyle volume at this diameter range, illustrating the significant Doyle penalty for small to mid-size hardwood logs in Appalachian markets. The stand tally feature lets the forester accumulate all 120 trees and sum the total without leaving the calculator.

Southern Yellow Pine Plantation Cruise in Lowndes County, Georgia

A timber buyer assessing a 25-year-old Southern Yellow Pine plantation in Lowndes County, Georgia estimates volume on a sample of trees. Average DBH in the merchantable size class: 14 inches. The plantation’s spacing and management history suggest good stem form, so the buyer uses form class 78 (well-managed pine plantation). Average merchantable height: 3 logs. Bark factor for SYP: 0.86. DBH inside bark: 14 x 0.86 = 12.0 inches. First log DIB: 12.0 x 0.78 = 9.4 inches. Taper per section: 1.5 inches (managed pine taper).

Doyle: Log 1: ((9.4-4)^2 x 16)/16 = 29.2 BF. Log 2: DIB=7.9 in, ((7.9-4)^2 x 16)/16 = 15.2 BF. Log 3: DIB=6.4 in, ((6.4-4)^2 x 16)/16 = 5.8 BF. Total: 50.2 BF Doyle per tree. 200 trees on the tract: 10,040 BF Doyle total = 10.04 MBF. At $220/MBF SYP sawtimber: $2,208.80 gross stumpage estimate. International equivalent: approximately 88 BF per tree, 17,600 BF total, showing how SYP on Doyle is significantly undervalued in volume terms.

Result: 50.2 BF Doyle per 14-inch SYP tree, 10.04 MBF for 200 trees, $2,208 gross stumpage at $220/MBF. The high form class (78) of the managed plantation gives a better first-log DIB than the same DBH tree would yield in an unmanaged stand at FC 65, producing 29 BF instead of 21 BF from the first log alone.

Michigan Sugar Maple Stand Valuation for Estate Settlement in Marquette County

An estate attorney in Marquette County, Michigan needs a timber value estimate for a 60-acre northern hardwood woodlot. A certified consulting forester performs the cruise using the International 1/4-inch rule, which is standard for formal appraisals in the Great Lakes states. The dominant species is Sugar Maple. Average DBH of the merchantable maple: 18 inches. Average merchantable height: 3 logs. Bark factor for Sugar Maple: 0.92. DBH inside bark: 18 x 0.92 = 16.6 inches. Form class 68 (average northern hardwood). First log DIB: 16.6 x 0.68 = 11.3 inches. Taper: 2.0 in per log.

International 1/4-inch by section: Log 1: (0.22×127.69 minus 0.71×11.3) x 4 = (28.09 minus 8.02) x 4 = 80.3 BF. Log 2: DIB=9.3 in, (0.22×86.49 minus 0.71×9.3) x 4 = (19.03 minus 6.60) x 4 = 49.7 BF. Log 3: DIB=7.3 in, (0.22×53.29 minus 0.71×7.3) x 4 = (11.72 minus 5.18) x 4 = 26.2 BF. Total: 156.2 BF International. 80 mature maple trees in the merchantable class: 12,496 BF = 12.5 MBF International. At $200/MBF International for Grade 2 Sugar Maple: $2,500 estimated stumpage value for the maple component.

Result: 156.2 BF International per 18-inch Sugar Maple tree, $2,500 estimated value for 80 trees at $200/MBF. The forester notes that Doyle scale on these same trees would be 147 BF total per tree (94% of International, converging at larger diameters), illustrating how the three rules approach each other as diameter increases above 18 inches.

Three Expert Tips for Accurate Standing Timber Volume Estimation in US Forests

Verify Form Class on a Sample of Trees Before Cruising the Full Stand

Form class is the most influential and most frequently misjudged input in standing timber volume estimation. A form class error of 5 points (using 65 instead of 70, for example) can shift the first log’s estimated small-end diameter by 0.7 inches on a 16-inch DBH tree, which changes the Doyle estimate for that log by several board feet. On a stand tally of 200 trees, this compounds into a meaningful total volume error. To calibrate your form class for the stand, fell 5 to 10 sample trees, measure the inside-bark diameter at 17 feet above the stump, and compute the actual form class. Average those measurements and use the result for the cruise. Published form class data from USDA technical publications and state forestry extension programs provide regional averages by species that are a good starting point when sample trees are not available.

Use the Per-Section Breakdown to Identify Which Trees Are Worth Cutting

The per-section table in this calculator reveals something that a simple total-tree volume estimate obscures: the contribution of each successive 16-foot log section to total tree value decreases rapidly with taper. In the typical second-growth hardwood tree with 2-inch taper per section and form class 68, the first log accounts for roughly 65 percent of total Doyle volume on a 3-log tree, and the third log may contribute as little as 6 percent. This means that a tree with 3 good logs is often more than twice as valuable as a tree with 1 good log, even at the same DBH. When evaluating a selective harvest proposal, knowing which trees in your stand yield 3 or 4 merchantable log sections versus 1 or 2 tells you far more than average DBH alone. The stand tally allows you to separate your trees by quality and prioritize accordingly.

Know the Minimum Merchantable Top Diameter for Your Buyer Before Setting Log Count

The formula stops counting log sections when the estimated small-end DIB drops below 4 inches (the Doyle formula’s mathematical minimum), but your buyer’s minimum merchantable diameter is almost certainly higher than 4 inches. Most US sawmills require a minimum of 6 to 8 inches inside bark at the small end of the smallest log they will buy. Pulpwood and biomass buyers may take smaller material, but at lower prices per unit. When counting merchantable 16-foot log sections, stop at the section where the estimated DIB reaches your buyer’s stated minimum, not at the calculator’s mathematical minimum. Overstating log count by including marginal upper sections that a buyer would reject leads to an inflated volume estimate that does not translate into actual stumpage income. Verify your buyer’s minimum diameter specification before finalizing any timber sale volume estimate.

Quick Reference: Doyle Board Feet per Standing Tree by DBH and Log Count

Estimated board feet Doyle per tree using Girard Form Class 68, 2-inch taper per 16-ft log, and a bark factor of 0.90 (typical eastern hardwood). Source: computed from the Girard Form Class formula as referenced in USDA Forest Products Laboratory technical publications and standard US timber cruise methodology. These are planning estimates, not certified cruise data.

DBH (in)1 log2 logs3 logs4 logsInt’l 3 logs
8″466619
10″1117181844
12″2033373879
14″30526063120
16″34485152101
18″50748082156
20″66100109112213
24″102162178183338

Frequently Asked Questions About Standing Timber Volume and Timber Cruising

What is DBH and why is it measured at 4.5 feet above ground?
DBH stands for Diameter at Breast Height. The 4.5-foot measurement height was standardized in the United States (versus 4.3 feet used in some European forestry traditions) to provide a consistent, reproducible measurement point across different foresters and measurement occasions. Trees tend to flare outward near the base due to roots and buttresses, and choosing a point just above that flare region gives a diameter that is more representative of the tree’s average stem diameter than a measurement near the ground would be. On hillside trees, the 4.5-foot measurement is taken on the uphill side. Trees with unusual features at exactly 4.5 feet (large bumps, galls, or forks) should be measured just above or below the feature, with a note in the cruise tally. DBH is outside the bark in all standard US timber cruise protocols, and the bark deduction is applied afterward to estimate inside-bark diameter for volume calculations.
What is the Girard Form Class and how does it affect tree volume estimates?
The Girard Form Class is a measure of how cylindrical or tapered the merchantable bole of a tree is. It is defined as 100 times the ratio of the inside-bark diameter at the top of the first 16-foot log (approximately 17 feet above the ground, above a 1-foot stump) to the inside-bark DBH. A form class of 68 means the tree’s first log small-end diameter is 68 percent of its inside-bark breast height diameter. Higher form class means a more cylindrical tree with less taper and more volume for its DBH. Form class 82 would mean an almost perfectly cylindrical upper stem, rare in nature. Form class 60 indicates a strongly tapered tree typical of open-grown hardwoods on poor sites. The form class determines the starting point for the per-section volume calculation: a higher form class gives a larger first-log small end, which yields more board feet per log under any of the three log rules. For a 16-inch DBH White Oak, changing form class from 60 to 80 changes the first log small-end DIB from 8.6 inches to 11.5 inches, which increases Doyle BF for that single log from 21.2 to 56.3, a 165 percent change from one input adjustment.
How do I estimate the number of merchantable logs in a standing tree?
The number of merchantable 16-foot log sections is determined by the height at which the stem reaches your buyer’s minimum acceptable diameter and by the presence of defects that make upper stem sections unsuitable for sawlog production. The practical approach in a timber cruise is to use a clinometer or other height measurement instrument to estimate the merchantable height in feet, then divide by 16. A tree with 48 feet of clean stem above the stump contains 3 full 16-foot logs. A tree with 56 feet of merchantable height would give 3 logs (48 feet) with an 8-foot remainder that might go to firewood or pulpwood rather than sawlogs. Foresters develop an ability to estimate merchantable height visually with practice, but new practitioners should verify their estimates against clinometer readings until they can do it reliably by eye. For this calculator, if a 4-log estimate seems high for your local stand conditions, try 3 logs and observe the change in total volume to understand the sensitivity.
What is a timber cruise and how do I conduct a basic one on my property?
A timber cruise is a systematic inventory of the standing timber on a property, producing a volume estimate and species composition summary that can be used for timber sale planning, property valuation, or management decisions. A basic timber cruise for a small woodlot might use a fixed-area plot method: establish circular or rectangular sample plots of fixed size (commonly 1/5th or 1/10th acre) at regular intervals across the property, tally all trees above a minimum DBH (typically 10 or 12 inches) within each plot, and use the plot tally to project stand-wide volume. More efficient cruises for larger properties use variable-radius plots with a prism (also called basal area factor cruising), where a simple prism tool held at eye level determines which trees are counted in each sample. State forestry agency extension services in most US states publish practical timber cruise guides for private landowners, and the USDA Forest Service publishes the National Forest Inventory protocols that form the basis for professional cruising standards. For any significant timber sale, hire a certified consulting forester to conduct the cruise.
Why do the per-section estimates vary so much between Doyle and International scale?
The gap between Doyle and International board foot estimates is most pronounced at small log diameters. When a standing tree’s upper log sections taper down to 6 or 7 inches inside bark at the small end, the Doyle rule assigns very few board feet to those sections (Doyle: ((7-4)^2 = 9 BF per 16-ft section) while International assigns a meaningfully larger amount (International: (0.22×49 minus 0.71×7) x 4 = 24.5 BF). The upper sections of a typical second-growth hardwood tree are often in exactly this diameter range where Doyle most severely underestimates yield. This means that Doyle scale consistently undervalues trees with multiple merchantable log sections relative to what a modern sawmill would actually recover, particularly in the 2nd, 3rd, and 4th sections. This is one reason timber buyers using Doyle scale often appear to undervalue tall, straight trees relative to short, stout trees of the same DBH: the tall tree’s upper sections, which contain real recoverable lumber, receive very little credit under the Doyle formula.
What is merchantable height and how does it differ from total tree height?
Total tree height is the distance from ground level to the very top of the tree, including the fine terminal branches and the leader. Merchantable height is the distance from the stump top (usually 1 foot above ground) to the point where the stem becomes too small, too defective, or too crooked to produce acceptable sawlogs. Merchantable height is always less than total height. For most eastern US commercial hardwood trees, merchantable height extends to roughly 50 to 70 percent of total height. A 90-foot tall White Oak might have 48 to 56 feet of merchantable stem (3 to 3.5 logs), while the remaining 34 to 42 feet of crown and upper stem provides structure for the tree but produces no sawlog value. Conifers in the Pacific Northwest often have higher merchantable-to-total height ratios because their crowns are smaller relative to stem length and they maintain a straighter form longer. For this calculator, you enter the number of 16-foot log sections in the merchantable portion, not the total height.
How accurate is the form class method compared to actual timber cruise volume tables?
The Girard Form Class method used in this calculator produces the same results as looking up values in published USDA timber cruise volume tables when the same form class, taper assumption, and log rule are used. Published volume tables are simply pre-computed versions of this formula at standard form class values (typically 68 and 70 for eastern hardwoods, 78 and 80 for southern pine). The method’s accuracy relative to actual mill recovery depends primarily on how well the assumed form class matches the tree being measured, and how accurately the number of merchantable log sections is counted. Studies comparing timber cruise estimates to actual mill tallies typically find that systematic cruise methods, properly applied by trained foresters, produce stand estimates within 10 to 15 percent of actual mill scale. Individual tree estimates may vary more widely. The calculator is most accurate when form class has been verified on sample trees in the stand rather than assumed from regional averages.
What is basal area and how does it relate to board foot volume in a standing timber cruise?
Basal area is the cross-sectional area of a tree’s stem at breast height, expressed in square feet. For a single tree, basal area = (DBH in inches / 24)^2 times pi, or approximately 0.005454 times DBH squared. For a stand, basal area per acre (BA/acre) is the sum of all individual tree basal areas on an acre, expressed in square feet per acre. Basal area is important in timber cruising because it is the basis for the variable-radius plot (or prism cruising) method, which is efficient for large-area cruises. A common target basal area for eastern hardwood stands managed for timber production is 80 to 120 square feet per acre. Basal area alone does not tell you board foot volume because it says nothing about tree height or merchantable stem length. To convert from basal area to board feet, you need form class and merchantable height information, which is essentially what this calculator’s per-section approach captures. Volume per unit basal area is a stand-level relationship that varies by species, site, and stand structure and is typically expressed as a volume-to-basal-area ratio derived from regional timber cruise data.
How do I account for tree defects in a standing timber volume estimate?
Tree defects that reduce recoverable board feet are applied as deductions to the gross log section volume computed by the formula. Common defects encountered in standing timber cruises include: rot columns (visible at the base from conks or shell rot, or estimated from species susceptibility and tree age), sweep or crook in the upper stem (visible from the ground; a curved log loses board feet to slab loss), lightning scars, large knot clusters in the first log (which reduce clear face length and lumber grade), cracks or checks, and evidence of insect damage or disease. The forester estimates what percentage of each log section’s theoretical volume is unusable due to defect and applies that percentage as a deduction. A log section with an estimated 30 percent defect would have its computed board feet reduced by 30 percent. This calculator computes gross sound-log volume only. In a formal cruise, defect deductions are applied in the field notebook or cruise software after the gross volume is established. For a quick planning estimate without visible defect, the gross volume from this calculator is appropriate.
What default form class should I use for common eastern US timber species?
Published default form class values from USDA Miscellaneous Publication 1034 and related references give the following typical ranges by species and region for the Girard Form Class. Eastern hardwoods, well-stocked stands: White Oak 60 to 68, Red Oak 62 to 70, Tulip Poplar 72 to 80 (exceptionally high form due to straight columnar growth), Sugar Maple 65 to 70, Black Walnut 62 to 68, Black Cherry 65 to 72, Yellow Birch 65 to 70, American Beech 62 to 68. Southern Yellow Pine (second growth, site index 65 to 75): 72 to 80. Eastern White Pine: 70 to 78. In the Pacific Northwest, Douglas Fir in managed stands: 65 to 78 depending on age and spacing. These are starting points. Actual form class varies by individual tree and stand conditions, and calibrating to your specific stand with a few measured sample trees dramatically improves cruise accuracy. The slider in this calculator allows you to explore the full range from 60 to 82 and see how form class affects your specific tree’s volume estimate.
Can I use this tool to estimate firewood cord volume from standing trees?
This calculator estimates board feet of sawlog potential, not cord volume for firewood. Firewood is measured by the cord (a stack 4 feet wide, 4 feet tall, and 8 feet long, containing approximately 128 cubic feet of stacked wood) or by weight. The Doyle and International formulas calculate recoverable lumber volume from logs suitable for a sawmill, which is a different measurement than total cubic volume including crown wood, branches, and small-diameter upper stem material. Trees too small or defective for sawlog production may still yield significant firewood volume, and large trees yield both sawlog board feet and firewood from slabs, edgings, and tops. If you are estimating the total wood available from a stand for a mixed firewood and sawlog harvest, you would use the board foot estimate for the sawlog portion and a separate cord volume estimate (based on species-specific cubic foot volume tables per tree) for the firewood component. State forestry extension programs publish combined sawlog and firewood volume estimates for the most common species in each region.
How many trees do I need to measure in a cruise to get an accurate stand estimate?
The number of sample trees needed for a statistically reliable cruise estimate depends on the variability of the stand and the precision you need. A simple rule used by many state forestry extension programs for private landowner assistance: measure at least 10 to 20 percent of the merchantable trees in each diameter class for small woodlots under 20 acres, and use a systematic sample intensity of 10 to 20 fixed-area plots per 100 acres for larger properties. For a timber sale appraisal submitted to a buyer or used in a legal matter, a sampling intensity that keeps the cruise error below 10 percent at the 90 percent confidence level is generally required, which typically means 20 to 40 sample plots per 100 acres depending on stand variability. A certified consulting forester will design the cruise sampling intensity for your specific situation. For a rough planning estimate on your own property, even 10 to 15 well-distributed sample trees in each major species and size class gives you a useful order-of-magnitude volume estimate.
What resources does the USDA Forest Service provide for private timber landowners?
The USDA Forest Service and its partner agencies provide several resources for private timberland owners. The Forest Service’s State and Private Forestry program works through state forestry agencies to provide technical and financial assistance for private forests. Most state forestry agencies offer free technical assistance visits by state service foresters, who will walk your property, give advice on management options, and help connect you with programs like the USDA EQIP (Environmental Quality Incentives Program) or CRP (Conservation Reserve Program) that may provide cost-sharing for timber stand improvements. The Forest Service’s National Forest Inventory and Analysis program, accessible through the FIA DataMart, provides regional timber volume and growth data that gives context for your stand’s productivity relative to regional averages. The USDA Forest Products Laboratory in Madison, Wisconsin publishes technical bulletins on log rules, volume tables, and timber measurement methods that are freely available at fpl.fs.usda.gov. State extension forestry programs through land-grant universities (Purdue, Penn State, Virginia Tech, Auburn, Michigan State, and others) publish landowner guides, cruise calculators, and market information for their respective regions.
What is a stumpage appraisal and when do I need one?
A stumpage appraisal is a formal estimate of the market value of standing timber on a property before any trees are cut, expressed as a dollar value per unit of volume (typically per MBF for sawtimber) or as a total dollar value for the timber to be harvested. You may need a formal stumpage appraisal for estate and probate purposes (valuing a decedent’s timber assets for tax reporting), property tax appeals (demonstrating that timberland has lower productive value than assessed), timber sale contracts (establishing a benchmark for evaluating buyer bids), conservation easement valuations (documenting current timber value before placing a restriction on harvesting), legal disputes over timber trespass or logging contracts, and timber sale financing (when a landowner wants to borrow against the value of standing timber). A formal stumpage appraisal must be prepared by a certified appraiser or a licensed Registered Forester with appraisal credentials, not by an online calculator. This calculator is a planning and educational tool that gives you a general sense of your timber’s volume and approximate value range, which is useful preparation for working with a professional appraiser but is not a substitute for a certified appraisal in legal or financial contexts.
How does merchantable height in feet convert to number of 16-foot logs?
Converting merchantable height from feet to number of 16-foot log sections: divide the merchantable height by 16. A 32-foot merchantable stem = 2 logs. A 48-foot stem = 3 logs. A 64-foot stem = 4 logs. A 50-foot stem would give 3 full logs (48 feet) with 2 feet remaining, which typically rounds down to 3 logs in a timber cruise. In practice, foresters count half-logs (8-foot sections) as 0.5 logs and enter them as the rounded number that makes sense for the tree. Some cruise software and tables use merchantable height directly in feet rather than as a log count. For this calculator, enter the log count as a whole number. If you are estimating from a tree height measurement: merchantable height in feet = total height minus crown length minus stump height. Crown base height varies widely by species; open-grown hardwoods may have crowns beginning at 20 to 30 feet while forest-grown trees may have clean stems to 60 or 70 feet. A clinometer reading for crown base is the most accurate field approach.
Where can I find published timber volume tables for my region and species?
Published timber volume tables covering major commercial species by US region are available from several sources. The USDA Forest Products Laboratory publishes volume tables and yield equations in various technical reports, available at fpl.fs.usda.gov. The USDA Forest Service’s Forest Inventory and Analysis program publishes regional yield tables at fs.usda.gov. State forestry agencies in most timber-producing states publish regional volume tables calibrated to local species and site conditions: the Virginia Department of Forestry, Tennessee Division of Forestry, North Carolina Forest Service, Georgia Forestry Commission, and similar agencies provide these free of charge, often as downloadable PDFs or as lookup tools on their websites. University extension forestry programs (Penn State Extension, Purdue Extension Forestry, University of Tennessee Extension, and many others) publish state-specific timber management handbooks that include volume tables, log rule references, and cruise methodology guides. For Pacific Northwest species, the USDA Pacific Northwest Research Station in Portland, Oregon publishes volume and yield information for Douglas Fir, western conifers, and Pacific Northwest hardwoods.

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Legal Disclaimer and Editorial Transparency

This Standing Timber Volume Calculator uses the Girard Form Class method: first log small-end DIB = DBH inside bark x (form class / 100), with each successive 16-foot section reduced by the user-entered taper. Board feet per section are calculated using the Doyle formula BF = ((D-4)^2 x L) / 16, the Scribner approximation BF = (0.79 x D^2 minus 2D minus 4) x L/16, and the International 1/4-inch formula BF = (0.22 x D^2 minus 0.71 x D) x L/4. All results are gross estimates for sound, defect-free log sections. Tree defects, broken tops, crook, sweep, and minimum merchantable diameter thresholds are not accounted for and must be applied separately. Species bark deduction factors are based on USDA Forest Products Laboratory averages and may vary by tree age and site. This calculator is for educational and planning purposes only and does not constitute a timber cruise, stumpage appraisal, or contract instrument. For timber sales, estate valuations, property tax matters, or legal proceedings, engage a licensed Registered Forester or certified timber appraiser. USCalculators.com is not affiliated with the USDA Forest Service or any state forestry agency. Authority references: USDA Forest Products Laboratory, Madison, WI; USDA Forest Service; USDA Southern Research Station. Tool last updated August 2026.