Natural Resource Biometrics

Basal Area

Basal area per tree is the cross-sectional area of a tree at breast height. It can be calculated from Diameter at breast height (DBH) by the following English formula:

where:

BA is basal area per tree in square feet.
DBH is the diameter at breast height in inches.
π is the constant 3.1415.

It can be calculated from Diameter at breast height (DBH) by the following metric formula:

where:

BA is basal area per tree in square meters.
DBH is the diameter at breast height in centimeters.
π is the constant 3.1415.

Basal area per acre is the sum of all the basal area per tree in the acre. Basal area per acre or hectare is a standard measure of the size-density relationship in a stand.

where:

BA/ac is the Basal area per acre,
BA_i is the Basal area per tree for the ith tree
W_i is the sample expansion factor weight.

Figure 1. An illustration of the basal area per acre. The basal area per tree is the cross-sectional area of each tree at breast height(the black ellipses). Basal area per acre would be the sum of these cross-sectional areas for all trees in an acre.