24-inch white oak, excellent, urban yard
Trunk area = π × 12² = 452.4 sq in × $75 = $33,929. Species 100% × condition 100% × location 100% keeps it whole: $33,929 (range $23,750–$44,108).
Educational estimate, not a certified appraisal. Online results are a ballpark (±30% or more). Insurance claims, legal disputes, and tax deductions need a written appraisal by a qualified arborist (ISA Certified or ASCA Registered). See FAQ.
$75 is the common US default. Move it to match your local market.
Tree health (condition)
Location
Estimated amenity value
$0
Conservative $0Aggressive $0
Show the math — factor breakdown
Straight, branch-free trunk only — not total tree height.
Defaults are illustrative — replace with a local buyer quote.
Estimated timber value
$0
Yield 0 board feetInternational 1/4″ rule
Compare all three log rules
Species factor table — 25 common trees
Search or tap a species to load it into the calculator. Factors are typical published values (0–100%); they vary by region — adjust to your local arborist guidance.
| Species | Species factor | Timber $/bf (illustrative) |
|---|
How the Trunk Formula works
The Trunk Formula, published by the Council of Tree and Landscape Appraisers (CTLA), is the standard method US arborists use to appraise a tree's amenity value — what the living tree is worth to the landscape:
Value = trunk area (sq in) × $/sq in × species × condition × location
Trunk area comes from DBH: area = π × (DBH ÷ 2)². A 24-inch DBH trunk has about 452 sq in of cross-section. At $75/sq in that's $33,929 before the three adjustment factors pull it toward reality: a silver maple in poor health in a forest keeps barely a tenth of that.
The species factor (0–100%) rewards long-lived, desirable, low-maintenance trees. The condition factor (excellent 100%, good 80%, fair 60%, poor 40%) discounts health and structure problems. The location factor (urban 100%, park 85%, forest 60%) reflects how much the tree contributes to its setting — a forest tree's amenity value is minimal, which is why Timber mode exists.
Timber value: from board feet to dollars
Timber buyers pay by the board foot (a 12″×12″×1″ slab = 144 cubic inches). Because a log is round and tapered, log rules estimate how many board feet a mill can actually saw from it:
- Doyle: ((D−4)² ÷ 16) × L — traditional in the eastern US; underestimates small logs.
- International 1/4″: (0.22D² − 0.71D) × L÷4 — the most accurate; the US Forest Service standard.
- Scribner: (0.79D² − 2D − 4) × L÷16 — common in the western US.
D is the log's small-end diameter in inches (this calculator assumes ~2 inches of taper below DBH — disclosed, not hidden), L is merchantable length in feet. Multiply board feet by your local price per board foot for the species. Prices are hyper-local: get a quote from a nearby mill or buyer before making decisions. Note: figured wood, burls, and veneer-grade logs trade in specialty markets this calculator doesn't price — get a specialty buyer quote for those.
Worked examples
18-inch silver maple, poor, park
Trunk area 254.5 sq in × $75 = $19,086 × 55% species × 40% condition × 85% park = $3,569. Same size, one-tenth the value — health and species dominate.
30-inch black walnut, 40 ft log, timber
Small-end ~28″: Doyle gives 1,440 board feet. At an illustrative $6/bf walnut price that's $8,640 in timber — versus ~$32,000+ as a living amenity tree. Living usually wins.
When this calculator is (and isn't) enough
- Good for: ballpark before calling an arborist, comparing quotes, deciding remove-vs-keep, curiosity about your backyard giant.
- Not enough for: insurance claims, lawsuits, tax deductions, or timber sales — those need a written appraisal by an ISA Certified Arborist or ASCA Registered Consulting Arborist following CTLA/ISA guidelines.
- Timber sales: always get 2–3 quotes from local buyers or mills; species, grade, and haul distance move the price more than any formula.
- How this differs from other calculators: most free tools (including the well-known Davey and ISA-style calculators) estimate amenity value only, with one fixed formula and no timber mode. This page adds timber valuation, all three log rules side-by-side, an adjustable $/sq in rate with a conservative–aggressive range, and a searchable 25-species factor table.
Looking for something else? This tool estimates monetary value. To estimate a tree's age from its diameter, use our tree age calculator; to plan planting distance and trees per acre, use our tree spacing calculator.
Frequently asked questions
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