Tree Age Calculator

You can use this simple tree age calculator to determine the estimated age of living trees. Simply use a measuring tape to measure the circumference of the tree, input the type of tree, and then click on the "Calculate" button to calculate the tree's age.

Estimating Tree Age

It can be very difficult to calculate the age of a tree if you don't know when it was planted. However, it is possible to estimate the tree's age through an approximation technique that is based on the circumference of its trunk.

This method, which was first proposed by the International Society of Arboriculture (ISA), relies on a simple formula that uses the tree diameter at breast height (DBH), which is the tree's diameter at a point of 4.5 feet above the ground.

How to Calculate the DBH

First, take a measuring tape and measure the circumference of the tree at a point of 4.5 feet above the ground. Then divide this measurement by 3.141592 (Pi). This is the DBH of the tree.

CBH (inches) / Pi = DBH (inches) , where Pi is the constant (3.141592).

Next, use the Tree Species & Growth Factors table to find the growth factor associated with the species of tree.

You can then estimate the age of the tree by multiplying this growth factor by the DBH in inches.

DBH (inches) × Growth Factor = Estimated Age of Tree (years)

Example: Let's say we want to estimate the age of a white oak that has the following features:

  • Circumference: 80 inches
  • Diameter: 25.46 inches (80 divided by 3.141592)
  • Growth Factor: 5.0
    • When we input these details into the equation, we have the following:

      25.46 × 5.0 = 127.323

      The estimated age of the white oak is 127 years old.

Tree Age Calculator


Note: It is important to note that the data provided in the table is more precise for trees that are grown in a forest environment as these are typically thinner than those found in open conditions. Trees that are in urban environments tend to suffer from being exposed to stressors such as pollution, inhibited growing areas, and damage.

Tree Species & Growth Factors
Species Growth Factor
American Beech 6
American Elm 4
American Sycamore 4
Austrian Pine 4.5
Basswood 3
Black Cherry 5
Black Maple 5
Black Walnut 4.5
Black Willow 2
Box Elder 3
Common Horsechestnut 8
Colorado Blue Spruce 4.5
Cottonwood 2
Dogwood 7
Douglas Fir 5
European Beech 4
European White Birch 5
Green Ash 4
Honeylocust 3
Ironwood 7
Kentucky Coffee Tree 3
Littleleaf Linden 3
Northern Red Oak 4
Norway Maple 4.5
Norway Spruce 5
Pin Oak 3
Quaking Aspen 2
Redbud 7
Red Maple 4.5
Red Pine (Norway Pine) 5.5
River Birch 3.5
Scarlet Oak 4
Scotch Pine 3.5
Shagbark Hickory 7.5
Shingle Oak 6
Shumard Oak 3
Silver Maple 3
Sugar Maple 5.5
Sweetgum 4
Tulip Tree 3
White Ash 5
White Birch 5
White Fir 7.5
White Oak 5
White Pine 5
Yellow Buckeye 5

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