Tree Age Calculator
Estimate a tree's age from trunk circumference and species.
About this tool
Measure the trunk's circumference at chest height (1.4 m or 4.5 ft) in inches or centimetres and choose the species. The tool calculates the diameter and an estimated age, plus the simple UK girth rule.
Measuring a tree's age
You can estimate a living tree's age without coring or cutting it. Measure the girth (circumference) of the trunk about 1.4 m (4.5 ft) above the ground, the standard 'diameter at breast height' (DBH) position, and divide by ฯ to get the diameter. Multiply the diameter in inches by the species' growth factor, the average number of years to add an inch of diameter. Fast growers like cottonwood and aspen have factors around 2, maples 3 to 5.5, oaks 3 to 5, and slow growers like dogwood, redbud and horse chestnut 7 or 8. A white oak 80 inches round is about 25.5 inches across, so at a factor of 5 it's roughly 127 years old; a silver maple of the same girth might be only about 76. The UK Woodland Trust's rule of thumb, roughly 2.5 cm of girth per year for a tree growing in the open, is shown too. Honest limits: these are estimates. Growth depends on soil, water, light and climate, trees in crowded woodland grow more slowly than they look, and the factors are averages from North American conditions. Only counting rings in a core sample gives an exact age. The plant spacing calculator and the circle calculator are related.
Frequently asked questions
How do you tell how old a tree is without cutting it?
Measure the circumference at chest height, divide by ฯ for diameter, and multiply by the species growth factor.
What is a tree growth factor?
The average number of years a species takes to add one inch of trunk diameter.
How old is a tree with a 100 cm girth?
About 40 years by the UK 2.5 cm-per-year rule, but species and conditions change this a lot.
Where should I measure a tree's circumference?
About 1.4 m (4.5 ft) above the ground, the standard breast-height position.
Is my data sent anywhere?
No. Everything is calculated in your browser, and nothing is stored or sent.