|This article does not cite any references or sources. (February
2007)| In most countries, this is usually a measurement taken at
the diameter at breast height (1.3m or 4.5ft) of a tree above
the ground and includes the complete diameter of every tree,
including the bark. Measurements are usually made for a plot and
this is then scaled up for 1 hectare of land for comparison
purposes to examine a forest's productivity and growth rate. To
estimate a tree's basal area , use the tree's diameter at breast
height in inches with the following formula: (Note: The factor
of 144 is there to convert from Sq Inches to Sq Feet) This
formula simplifies to: The result will be in ft2. For the DBH in
cm use: The result will be in m2. The basal area of a forest
stand can be found by adding the basal areas (as calculated
above) of all of the trees in an area and dividing by the area
of land in which the trees were measured. Basal area is
generally expressed as ft2/acre or m2/ha. A wedge prism can be
used to quickly estimate th