You can estimate the approximate size and age of a tree on your property. Size estimations can be done for any tree. If you want to estimate the age, you’ll first need to know the tree species. If you don’t know the species, perhaps you know someone who is tree knowledgeable that can help. There are also three ways to determine precisely a tree’s age and one of them is not harmful.
Estimate the Size of a Tree
There are several dimensions that are used to define the size of a tree:
- Circumference – This of course is the distance around the tree in inches measured at breast height, or more precisely 4.5 feet from the ground. If the tree forks below 4.5 feet from the ground (a good example is River Birch trees), measure the largest stem.
- Diameter at Breast Height (DBH) – once you have the circumference at breast height, just divide by 3.14 (which is the value of pi). Just as with Circumference, DBH is stated in inches.
- Height – the height of the tree is the distance from the ground to the tip of the tallest branch measured in feet.
- Average Crown Spread – this is the average of two measurements – the width of the crown in one direction and the width of the crown measured at right angles to the first width. These measurements and the resulting spread will be in feet.
The Georgia Forestry Commission has good information with diagrams that illustrate how to take these measurements on their page how to score a Champion Tree.
Estimate the Age of a Tree
There is only one way we know to estimate the age of a living tree is to create a table by recording each year the diameter (DBH) of many trees of the same species. The average measurements for all of the trees year by year are converted into something known as a ‘growth factor’. Then to estimate the age of any tree of the same species, reverse the process by multiplying a species’ growth factor by its DBH.
We put together a page with two different ways to use growth factors to estimate the age of your tree.
Determine the Age of a Tree
You may be able to determine precisely the age of your tree: 1) count the rings after it’s been cut down, 2) ask someone who knows what they are doing to core-bore into the tree and count the rings of the resulting core, or 3) rely on first-hand accounts and historical records.
The first two are less than desirable. The first means you’ve lost the tree and the second can be very harmful, since the boring will leave a hole which insects may enter and damage or kill the tree. The third, relying on first-hand information, is of course ideal.
References and Additional Information
 Georgia Forestry Commission: Georgia Champion Tree Program – How to Score a Champion Tree