Have you ever gazed upon a grand tree and pondered its age? Determining how old a tree is can yield important information about its past, growth trends, and the care it needs.

A simple way to estimate the age of a tree is to measure the trunk’s circumference (at chest height) and divide by Pi (3.14) to get the diameter. Then you multiply the tree’s diameter by the tree species growth factor.

How to Tell the Age of a Tree


Tree Species: Norway Spruce
Trunk Circumference: 86 inches
Growth factor: 5


86” circumference / Pi (3.14) = 27.39 (diameter of the trunk)

x 5 (Growth factor) = 136 Years

This formula allows you to manually work out the age of a tree. Or you could use this tree age calculator.

Tree Age Calculator

Estimated Tree Age: 0 years

Measuring Trunk Circumference for Age Estimation

Measuring Trunk Circumference for Age Estimation

One of the first steps in estimating a tree’s age is to measure its circumference. This involves wrapping a measuring tape around the tree trunk at breast height, which is approximately 4 feet (1.2m) from the ground.

Converting circumference to diameter

Once you have the tree’s circumference, you’ll need to convert it to diameter to proceed with age estimation. The formula for this conversion is simple: diameter = circumference/pi (3.14).

For example, if a tree has a circumference of 10 feet, its diameter would be calculated as 10/pi, which equals approximately 3.18 feet. This diameter measurement will be essential for the next step in estimating the tree’s age.

Calculating Tree Diameter and Growth Factor

With the tree’s diameter in hand, we can now introduce the concept of growth factors to our age estimation process. Growth factors are specific to each tree species and represent the average tree growth rate.

We can approximate the tree’s age by multiplying the diameter by the growth factor for a specific tree species.

Calculating Tree Diameter and Growth Factor

List of tree species growth factors

TreeGrowth Factor
Growth Factor
American beech62.36
American elm41.57
Austrian Pine4.51.77
Red pine5.52.17
White pine51.97
Colorado blue spruce4.51.77
Norway spruce51.97
Scotch pine3.51.38
White pine51.97
Black cherry51.97
Black maple51.97
Norway maple4.51.77
Red maple4.51.77
Silver maple31.18
Sugar maple5.52.17
Black walnut4.51.77
Northern red oak41.57
Pin oak31.18
Scarlet oak41.57
Shingle oak62.36
Shumard oak31.18
White oak51.97
Bradford pear (invasive non-native, not recommended31.18
Common horsechestnut83.15
Douglas fir51.97
European beech41.57
European white birch51.97
Green ash41.57
Kentucky coffee tree31.18
Littleleaf linden31.18
Red pine5.52.17
River birch3.51.38
Scotch pine3.51.38
Shagbark hickory7.52.95
Sweet gum41.57
Tulip tree31.18
White ash51.97
White fir7.52.95
Yellow buckeye51.97

Estimating Tree Age with Diameter and Growth Factor

Now that we have the tree’s diameter and the growth factor for its species, we can estimate its age by multiplying these two values together. This method provides a rough approximation of the tree’s age, which can be useful for various purposes, such as understanding the tree’s growth patterns and determining appropriate care strategies.

Let’s consider a few example calculations for estimating tree age1 using diameter and growth factors. For a Big Leaf Maple tree with a diameter of 2 feet, we would multiply the diameter (2) by its growth factor (4.7) to get an estimated age of 9.4 years.

Similarly, for a Pin Oak tree with a diameter of 3 feet, we would multiply the diameter (3) by its growth factor (3.0) to get an estimated age of 9 years. These examples illustrate how diameter and growth factors can be combined to estimate the age of various tree species.

Limitations of this method

While estimating tree age using diameter and growth factor can provide useful insights, it’s important to recognize the limitations of this method. First, this approach is not always reliable and can be influenced by factors such as tree species, environmental conditions, and age.

Additionally, errors in measuring a tree’s diameter can significantly impact the accuracy of the age estimate. Nevertheless, this method can still be a helpful tool for gaining a general understanding of a tree’s age.

Alternative Methods for Estimating Tree Age

Alternative Methods for Estimating Tree Age

In addition to the diameter and growth factor method, there are several alternative approaches to estimating tree age, but most involve drilling core samples to count rings or for carbon dating.

Each method has its advantages and disadvantages, but we are best just estimating with the above method and leaving the tree be. Drilling into it can have negative implications as water, rot, pests, and diseases can make their way into any opening, which will cut the life of the tree short.

Radiocarbon dating (for certain tree species)

Radiocarbon dating is a method used to estimate tree age for certain tree species. This approach involves analyzing the chemicals within the tree to determine its age.

While radiocarbon dating can be a useful tool for estimating tree age in some cases, it is also subject to limitations, such as the potential impact of illness and environmental factors on the tree. As with any method, it’s essential to consider the unique characteristics and limitations of radiocarbon dating when using it to estimate tree age.


Dendrochronology2 can be used to tell when the tree has naturally died or fallen if the calendar year dates of tree growth rings can be determined.

If the tree is on well-drained, moist soil for a period of 20 years it can grow up to 40 ft.

As an individual tree, the current record holder for the oldest tree in the world is the Great Basin bristlecone pine trees from California and Nevada. The tree-ring cross-referencing has proved to be almost 5,000 years old.

  1. Lindsey Purcell, (2018) How Old Is My Tree? <https://www.purduelandscapereport.org/article/how-old-is-my-tree/> Accessed: 02-03-2024
  2. Amy Tikkanen, (2020) Dendrochronology. <https://www.britannica.com/science/dendrochronology> Accessed: 02-03-2024
Ben McInerney
Author: Ben McInerney - Ben is a qualified arborist with 15 plus years of industry experience in Arboriculture. He ran a successful tree service before turning to writing and publishing. Ben is dedicated to providing users with the most accurate up-to-date information on everything trees.