How to Determine the Age of a Tree
Instead of cutting down a tree and counting its growth rings or using an increment borer to find out how old a tree is, you can make a fairly good estimate of the age of a tree by using a simple formula published by the International Society of Arboriculture.
First, determine tree diameter in inches measured at 54 inches above ground level (remember that diameter equals circumference divided by 3.14 (pi)).
Next, use the table below, which assigns a growth factor to various tree species. Multiply the diameter in inches by the appropriate growth factor to determine the estimated age of your tree.
Let's use the white oak, for example. It has a growth factor of 5. If our white oak has a diameter of 22 inches, we'd multiply that by 5 to get an estimated age of 110 years (diameter in inches x growth factor = tree age)
Tree species and related growth factors
| Tree | Growth Factor |
|---|---|
| American beech | 6 |
| American elm | 4 |
| American sycamore | 4 |
| Austrian pine | 4.5 |
| Black cherry | 5 |
| Black maple | 5 |
| Black walnut | 4.5 |
| Bradford pear (invasive non-native, not recommended) | 3 |
| Common horsechestnut | 8 |
| Colorado blue spruce | 4.5 |
| Cottonwood | 2 |
| Douglas fir | 5 |
| European beech | 4 |
| European white birch | 5 |
| Green ash | 4 |
| Ironwood | 7 |
| Kentucky coffee tree | 3 |
| Littleleaf linden | 3 |
| Northern red oak | 4 |
| Norway maple | 4.5 |
| Norway spruce | 5 |
| Pin oak | 3 |
| Redbud | 7 |
| Red maple | 4.5 |
| Red 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 |
| Sweet gum | 4 |
| Tulip tree | 3 |
| White ash | 5 |
| White fir | 7.5 |
| White oak | 5 |
| White pine | 5 |
| Yellow buckeye | 5 |
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