Tree Age Estimator
Estimate a tree's approximate age based on its trunk diameter at breast height (DBH) and species growth factor.
Formula
Estimated Age (years) = DBH (inches) × Growth Factor
Where:
- DBH = Diameter at Breast Height, measured at 4.5 feet (1.37 m) above ground
- Growth Factor = Species-specific average years of growth per inch of diameter
- If circumference (CBH) is provided: DBH = CBH ÷ π
- Confidence range is ±20% of the estimated age
Example: A Red Oak (Growth Factor = 4.0) with a DBH of 18 inches:
Age ≈ 18 × 4.0 = 72 years (range: 58–86 years)
Assumptions & References
- Growth factors are species-specific averages developed by the International Society of Arboriculture (ISA).
- DBH is measured at 4.5 feet (breast height) above ground level on the uphill side of the tree.
- This method assumes average growing conditions; trees in poor soil or harsh climates may be older than estimated.
- Growth factors range from ~2 (fast-growing species like Willow) to ~7+ (slow-growing species like Ironwood).
- The ±20% confidence range reflects natural variability in growth rates within a species.
- For precise age determination, core sampling (dendrochronology) is recommended.
- Reference: Bernatzky, A. (1978). Tree Ecology and Preservation; ISA Best Management Practices.
- This tool is intended for educational and general estimation purposes only.