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Measuring Tree Diameter for Urban Tree Inventories

Publication Number: IS2007
View as PDF: IS2007.pdf
Sea Grant Mississippi-Alabama

Diameter at breast height (DBH) is the diameter of the tree stem at 4½ feet aboveground. Measuring DBH of a tree for an urban forest inventory is easy when you have a diameter tape. A few points are important to keep in mind. First, a diameter tape (D-tape) is a breakable instrument. If you are not careful, the spring within the housing can break, resulting in the tape’s inability to recoil and becoming a tangled web of metal. Second, the metal strip can be sharp, so be careful when handling the tape. Third, MSU Extension recommends a 100-foot diameter tape with distance in tenths of inches. One side of the tape can measure distance, while the other side of the tape is calibrated to pi in order to measure diameter. 
 

Procedure

Standing upslope from base of the tree, use your right hand to hold the casing and your left hand to hold the end of the tape. Wrap the tape around the tree, remembering to measure at 4½ feet above where the tree meets the ground and keeping the tape level. Avoid wrapping the tape around vines or deformities. If the tree has a deformity at breast height, measure the diameter just above the deformity. Line up the end of the tape (zero) with the corresponding metric on the diameter side of the tape. The matching metric is the tree’s DBH. Depending on the measurement’s objective, you may want to record to the nearest tenth or nearest inch.
An image showing the inches side of a diameter tape.
Diameter tape: Inches side of measurement.
An image showing the diameter side of a diameter tape.
Diameter tape: Diameter side of measurement.
An image showing the proper technique for measuring the diameter of a tree.
 

Additional Information

For more information, see Publication 2882 A Step-by-Step Guide to Taking Urban Forest Inventory Measurements.


Information Sheet 2007 (POD-01-16)

By Dr. Jason Gordon, Assistant Extension Professor, Forestry.

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