Trunk Formula Method Explained

The Trunk Formula Method (TFM) is the industry-standard valuation technique for trees that are considered too large to be replaced with nursery stock. It is defined in the Guide for Plant Appraisal, 10th Edition (CTLA).

Tree Appraisal Pro automates this complex calculation for you. Here is how the math works:

Step 1: Physical Size

We calculate the cross-sectional area of the trunk based on the diameter (DBH) you provide.

Trunk Area = 0.7854 × DBH²

Step 2: Basic Price

We determine the replacement cost of a perfect tree of this size using your Unit Cost (e.g., $6.00/in²).

Basic Price = Trunk Area × Unit Cost

Step 3: Depreciation

We depreciate the value based on the three key rating factors you provide (Species, Condition, and Location).

Value = Basic Price × Species % × Condition % × Location %

The final Appraised Value represents the contributory value of the tree to the property, adjusted for its specific health, structure, and placement.