How Old is My Tree?
You don't need to cut down a tree and count its growth rings or use a hole boring tool to find out how old it is. You can make a good estimate of a tree’s age using this simple formula published by the International Society of Arboriculture.
Note: The growth factors listed below are more accurate for forestgrown trees, which grow thinner than street trees. Stressed trees from urban situations—such as inadequate soil, damage or topping—will grow slower and weaker than healthy trees.
 First, determine tree diameter in inches measured at 54 inches above ground level.
 Remember that diameter equals circumference divided by 3.14 (pi). If you're using a standard tape measure, make sure to multiply the feet by 12 to receive your circumference in inches. Example: 14 feet multiplied by 12 would be 168 inches. Then divide 168 by 3.14 (pi) to equal 53.50 inches in diameter.
 Use the following table, 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 Scarlett Oak, for example. It has a growth factor of 4. If our Scarlett Oak has a diameter of 53.50 inches, we would multiply that by 4 to get an estimated age of 214 years.
Note: The growth factors listed below are more accurate for forestgrown trees, which grow thinner than street trees. Stressed trees from urban situations—such as inadequate soil, damage or topping—will grow slower and weaker than healthy trees.
Tree Growth Factor



Tree Measuring Guide
1. The tree tapers in such a way that the diameter at a point below 4.5 ft is actually smaller than the diameter at 4.5 ft. Measure diameter at the smallest point and record the height at which diameter was measured on the data sheet.
2. Tree has branches or bumps which interfere with DBH measurement. Measure DBH below the branch or bump. Some references say to measure a foot below the branching point, which assumes this point is the smallest diameter of the trunk below 4.5 ft. US Forest Service measures DBH immediately above point were bumps or branches cease to affect diameter of the stem. The underlying concept is to measure the diameter that would be closest to the expected DBH if branches or other irregularities were not present. Record the height at which the diameter measured.
3. Vertically growing tree is on a slope. There are several commonly accepted ways to find the DBH height. Probably the easiest method is to measure diameter 4.5 ft from the ground on the upper side of the slope. This method is used by the US Forest Service. Some references (e.g., International Society of Arboriculture's Tree Appraisal Manual) say to measure 4.5 ft from the midpoint of the trunk along the slope. However, finding the location of the trunk midpoint is probably subject to more error than finding the upper side of the trunk, so the USFS method is likely to be more repeatable than the ISA method.
4. Tree leans. There are several commonly accepted ways to find the DBH height. The US Forest Service measures 4.5 ft up the stem in the direction of the lean. Some references (e.g., ISA) say to measure 4.5 ft from the midpoint of the lean. As noted under 3 above, the USFS method is probably less prone to error and more readily repeatable by different observers.
5. Tree forks below DBH or near DBH. The measurement is recorded at the narrowest part of the main stem below the fork. The height of the DBH measurement and the fork should be noted (e.g., 3 ft diameter @ 2 ft [Forks @ 4 ft]).
6. Tree splits into several trunks close to ground level. Measure DBH of each trunk separately, using the principals shown in categories 15 above. The DBH for the tree is found by taking the square root of the sum of all squared stem DBHs.