Calculator
Example Data
Use these sample measurements to see how results are computed. You can load them into the results table with one click.
| Species | Type | Value | Unit |
|---|---|---|---|
| White Oak (GF 5.0) | diameter | 20 | in |
| Red Maple (GF 4.5) | circumference | 100 | cm |
| Douglas Fir (GF 5.0) | diameter | 30 | in |
| London Plane (GF 3.5) | circumference | 60 | in |
| White Pine (GF 5.0) | diameter | 45 | cm |
Results
| # | Date & Time | Species | GF | Method | Measured | Unit | DBH (in) | Estimated Age (yrs) | Notes | Delete |
|---|
Formula Used
Estimated Age (years) ≈ DBH (inches) × Growth Factor (GF). DBH is measured at 4.5 ft (1.37 m) above ground. If you recorded circumference, first convert to DBH using DBH = circumference ÷ π. If you recorded in centimeters, convert to inches using inches = centimeters ÷ 2.54.
Growth factors are average values for typical site conditions. Real ages may differ with soil, climate, competition, and tree health.
Species Growth Factors (GF) (reference set)
- Red Maple — 4.5
- Silver Maple — 3.0
- Sugar Maple — 5.5
- White Oak — 5.0
- Red Oak — 4.0
- Pin Oak — 3.5
- American Elm — 4.0
- Cottonwood — 2.0
- Douglas Fir — 5.0
- White Pine — 5.0
- Norway Spruce — 4.5
- Black Walnut — 4.5
- Sweetgum — 4.0
- Tuliptree — 3.0
- London Plane — 3.5
- Sycamore — 4.0
How to Use This Calculator
- Select the species that best matches your tree. The dropdown shows its growth factor.
- Choose whether you measured diameter (DBH) or circumference (CBH) at 4.5 ft above ground.
- Enter the measurement value and unit. The calculator handles unit conversion automatically.
- Optionally add notes such as site, slope, or observations.
- Click Calculate & Add Row to append results to the table. Use the buttons to export CSV or PDF.
FAQs
1) How accurate is the estimate?
It is a rule‑of‑thumb based on average growth factors. Site and health conditions can shift age by decades for large trees.
2) Where do I measure?
Measure at 4.5 feet (1.37 m) above ground. If the trunk is irregular there, choose the smallest diameter below that height.
3) Can I use centimeters?
Yes. Enter cm in the unit selector. The tool converts to inches internally before applying the growth factor.
4) Which species should I pick?
Pick the closest match. If unknown, try two or three likely species to see a range of ages.
5) Why use circumference?
Some field guides record CBH. The calculator converts circumference to diameter by dividing by π to compute DBH.