Tree age estimate calculator
Type a trunk diameter and pick a species to see the diameter times the growth factor from a published table, which gives an estimated age in years. The table's author calls the method a very rough estimate.
Checked against the sources at the bottom of this page on October 8, 2026. Published tables are revised: the source has the last word.
Work it out
How the answer is worked out
Estimated age in years = the trunk diameter in inches times the growth factor for the species. A diameter typed in centimetres is changed to inches first, at 2.54 centimetres to the inch.
A trunk measure typed as a circumference is first divided by pi to give the diameter. This calculator takes the diameter itself.
What the sources say
The factors are the eighteen species in a table in the Purdue Landscape Report issue How Old Is My Tree?, which gives the formula as diameter at breast height times a growth factor. The report's worked example is a white oak of 22 inches, factor 5.0, which gives 110 years. The report says its method is only a very rough estimate, since growth factor tables assume a steady link between diameter growth and years of growth.
The report says woodland and city trees grow differently, with tree growth rates affected by water, climate, soil, root stress, competition for light and vigor, and that growth rates vary within a genus. Its author describes a personal deduction of 25 percent from the age for park or residential trees, and calls that an anecdotal deduction based on experience. This calculator does not apply it. Neither page gives an error range.
Separately, a page from the Grosse Ile Nature and Land Conservancy prints the same method and the same figures for these species, and adds aspen at 2.0. It calls the result an approximate age.
The report measures breast height at 4.5 feet above the ground, and the Forest Service's inventory field guide also sets breast height at 4.5 feet. Other countries set it elsewhere: see the table of measuring heights on the Tools page.
Arithmetic only. The answer is only as good as the numbers entered. It is not a plan or a safe working load for any job.
Sources
- Purdue Landscape Report, How Old Is My Tree? by Lindsey Purcell, issue 18-04, April 10, 2018 (PDF as hosted by Eagle Creek Park), read October 8, 2026
- Grosse Ile Nature and Land Conservancy, Estimating the Age of a Tree, read October 8, 2026
- USDA Forest Service, Forest Inventory and Analysis National Core Field Guide, version 9.3, September 2023, read October 8, 2026
- NIST, Guide for the Use of the International System of Units (SP 811), Appendix B.8 factors for units listed alphabetically, read October 8, 2026