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Finding Tree Diameter (DBH)

Page history last edited by Nancy Brachbill 9 years ago


Here's How...


  • Diameter is the width of a circle or cylinder; in this case the trunk of the tree.


  • Tree trunks have taper (they are slightly cone-shaped), such that they are wider at the base and narrower further up.


  • Thus, diameter will vary based on how high up on the trunk of the tree you measure it.


  • A standardized height for measuring tree diameter has been established.


  • This is known as breast height, which is defined as 4.5 feet (54 inches) above the ground, on the uphill side of the tree. 


  1. Use a measuring tape to figure out how high up breast height is on you.
  2. Memorize this spot (e.g. the next to the top button on your shirt or coat) so that as you stand next to a tree, you know where to measure diameter.
  3. Measure the tree circumference (distance around) at 4.5 feet from the ground in centimeter units.
  4. Calculate the diameter of your tree using the following formula:
    1. Circumference ÷  pi (3.14) = Diameter



                         _________________   ÷  pi (3.14) =   _____________________

                      circumference (include units)                        diameter (include units)

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