How to Calculate Density by Knowing the DBH

In forestry, density measures the fraction of an area covered by trees. A greater number of trees in a plot corresponds with a more densely wooded area. The trees' sizes matter as well. Thicker trees lead to a more dense forest. Complicating matters, each trunk's width varies depending on where you measure it. By convention, foresters consider the trunk's basal area, which is the its cross-sectional area at breast height. This value depends on the trunk's diameter at breast height (DBH).

Instructions

- 1
  Divide the tree's DBH by 2. For instance, if it has a DBH of 11 inches: 11 ÷ 2 = 5.5 in. This is the tree's radius at breast height.
- 2
  Square the radius: 5.5² = 30.25 in².
- 3
  Multiply the answer by pi, which is approximately 3.142: 30.25 --- π = 95.03 in². This is one tree's basal area.
- 4
  Divide this answer by 144 to convert it to square feet: 95.03 ÷ 144 = 0.66 ft².
- 5
  Multiply this answer by the number of trees in one hectare, which is a unit of area equal to 2.47 acres. For instance, if the area contains 350 trees: 0.66 --- 350 = 231. This is the area's density, measured in square feet per hectare.

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