WW-03025     Reviewed 1998  

Sampling and Measuring Timber in the Private Woodland

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Estimating Tree Diameter

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Tree diameter is the most important measurement of standing trees. Diameter is measured at 4 1/2 feet above the ground (foresters refer to this as the diameter at breast height, or DBH) on the main stem. DBH's are usually measured to the nearest 1/10-inch and recorded by one-inch classes. As an example, trees with a DBH between 5.6 inches and 6.5 inches would be assigned a value of 6 inches when information is recorded.

A steel diameter tape, calibrated to permit direct tree diameter readings, is frequently used to measure tree DBH. Wrap the tape around the tree at breast height perpendicular to the lean of the tree (Figure 2), standing on the uphill side of the tree. If there are branches or other projections at DBH, place the tape above them. If a fork appears below breast height, consider the tree to be two separate trees, recording separate measurements for each tree.

If a diameter tape is not available, measure tree circumference by wrapping a cloth tape or string around the tree at breast height. Divide the resulting circumference by 3.14 to determine DBH.

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