Almighty Calculator

Tree Appraisal Calculator

The trunk formula scales a nursery tree's cost by trunk area, so value = trunk area × unit nursery cost per square inch, less depreciation for condition and limitations, plus added costs.

in
For the reproduction cost method use the subject tree. For functional replacement use the size of tree that would restore the lost function. Measure as the Guide specifies.
in
The largest nursery tree readily available, measured the way the nursery sells it.
$
$/in²
Only used when you choose the regional option.
%
The appraiser's rating of health, structure, and form.
%
100% means no limitation on the tree's function.
%
100% means no external limits such as poor site or legal constraints.
$
$
$
$
$
Total appraised cost (before rounding)
12,000$
Cross-sectional area of the tree to be replaced314.2 in²
Cross-sectional area of the nursery tree12.57 in²
Unit nursery tree cost47.75 $/in²
Basic functional replacement cost (line 11)15,000 $
More results (2)
Depreciated basic cost (line 12)
12,000 $
Total additional costs (line 13)
0 $

This tool does only the arithmetic of the worksheet. The condition and limitation ratings, the choice of method, the regional unit cost, and the additional costs are the appraiser's judgment. Use the Guide for Plant Appraisal and, for legal, insurance, or tax purposes, a qualified appraiser.

Show the math

Area to replace = 0.7854 × 20² = 314.2 in²
Unit cost = $600 ÷ (0.7854 × 4² = 12.57 in²) = $47.75 per in²
Basic cost = 314.2 × $47.75 = $15,000
Depreciated = $15,000 × 80% × 100% × 100% = $12,000
Total = $12,000 + $0 additional = $12,000

Rounded the same way as the result above.

How it works

The Trunk Formula Technique values a large tree by extending the price of a nursery tree. It assumes cost grows with the cross-sectional area of the trunk, so the cost per square inch of the largest nursery tree you can buy sets a unit cost, and that unit cost is applied to the area of the tree being appraised.

The result is a cost to replace or reproduce the tree. In the 10th edition of the Guide it is then depreciated in three steps: for the condition of the tree, for functional limitations, and for external limitations, each expressed as a percentage. Costs such as cleanup, planting, aftercare, and hardscape are added afterward and are not depreciated.

Cross-sectional area = 0.7854 × D² Unit nursery tree cost = nursery tree cost ÷ nursery tree area (or a regional unit cost) Basic cost = area of tree to be replaced × unit cost Depreciated cost = basic cost × condition × functional limitations × external limitations Total = depreciated (or basic) cost + additional costs

Worked example

A 20-inch tree, replaced by scaling a $600, 4-inch nursery tree, rated 80% for condition and 100% for both limitations, with $1,500 of installation and aftercare:

  1. Area to replace = 0.7854 × 20² = 314.2 in²
  2. Unit cost = $600 ÷ (0.7854 × 4² = 12.57 in²) = $47.75 per in²
  3. Basic cost = 314.2 × $47.75 = $15,000
  4. Depreciated = $15,000 × 80% × 100% × 100% = $12,000
  5. Total = $12,000 + $1,500 additional = $13,500
InputValue
Trunk diameter of the tree to be replaced20 in
Replacement nursery tree trunk diameter4 in
Unit nursery tree cost comes fromThe nursery tree cost and diameter above
Nursery tree cost (installed cost excluded)600 $
Regional unit tree cost50 $/in²
Apply depreciation to the basic costYes (condition, functional limitations, external limitations)
Condition rating of the subject tree80 %
Functional limitations rating100 %
External limitations rating100 %
Additional cost: cleanup and removal0 $
Additional cost: nursery tree installation1000 $
Additional cost: aftercare500 $
Additional cost: hardscape0 $
Additional cost: other0 $
ResultValue
Cross-sectional area of the tree to be replaced314.2 in²
Cross-sectional area of the nursery tree12.57 in²
Unit nursery tree cost47.75 $/in²
Basic functional replacement cost (line 11)15,000 $
Depreciated basic cost (line 12)12,000 $
Total additional costs (line 13)1,500 $
Total appraised cost (before rounding)13,500 $

Assumptions and limits

  • Follows the calculation lines of the Guide for Plant Appraisal, 10th edition, Functional Replacement Method / Trunk Formula Technique worksheet. Earlier editions used different depreciation categories and treated installation cost differently.
  • The appraised tree's own diameter does not enter the functional replacement worksheet; the size of the replacement does. For the reproduction cost method, enter the subject tree's diameter as the tree to be replaced.
  • Ratings are percentages you assign after inspection. The Guide describes how to assess condition, but this tool does not rate a tree for you.
  • The final value is normally rounded by the appraiser; the Guide sets the convention.

Common questions

What is the trunk formula method?

A cost-approach method that scales the price of the largest nursery tree you can buy up to the size of the tree being appraised, using trunk cross-sectional area, then depreciates for condition and limitations.

What is a tree worth after storm damage or removal?

It depends on size, condition, species, and location, and on which method the appraiser uses. This tool shows how the trunk formula arithmetic works; a credentialed appraiser assigns the ratings.

How do I measure trunk diameter?

Follow the Guide: existing trees at the standard trunk height it specifies, and nursery stock the way nurseries measure caliper. Use the same convention for the tree being appraised and the nursery tree.

Do additional costs get depreciated?

No. The worksheet applies depreciation to the basic cost only and adds cleanup, installation, aftercare, hardscape, and other costs afterward.

Sources

Updated 2026-09-30