Diameter at Breast Height (DBH) is the standard for where to measure trees.

"Breast height" refers to the vertical location of the tree trunk directly in front of a person of average height's chest.

"Diameter" refers to the width of the tree trunk. There are two ways to find a tree's diameter:

1. Using a standard measuring tape to measure the tree's circumference, and then using the formula Diameter = Circumference / π
2. Using a DBH tape, which includes diameter markings that are pre-calculated from the above formula

See the video below for a video demonstration of DBH measurement (note: the tape used has a hook that keeps the base of the measurement in place. Some measuring tapes do not have this. In that case, you will have to hold it down with your hand, or a helper's hand.)