 When speaking with a forester or land manager, you may hear them use terms such as basal area or trees per acre to explain stand density, or the stocking or crowding of trees in a stand. These terms and their calculations will be used to make management decisions based on your goals. Trees per acre is the number of standing trees within an acre of land, but using trees per acre numbers alone does not provide any information on the size of the trees in a stand. Therefore, basal area should be included. Basal area expressed in square feet is the measurement of the cross-sectional area at breast height, or four and a half feet of a single tree, including the bark. Although both terms can be used to describe stand density and stocking levels, they are completely different. Combining trees per acre and tree or stand basal area estimates provides a better representation of density and the size of trees within a stand. Both values are needed for management decisions. To calculate the basal area for a specific tree, measure the tree's diameter at breast height, or dbh. Square that value and multiply times the forester's constant, 0.005454. The forester's constant is used to convert inches into square feet. This calculation is the area in square feet that this tree takes up in the forest. Basal area measurements can also be estimated on a per acre basis and are the sum of all cross-sectional areas of stems within a particular stand. Easy visualization of this would be to picture an acre of land with every tree cut off at four and a half feet. The sum of all the stumped surface areas would equal the square feet of basal area for that acre. Your forester will calculate basal area of your stand during a timber cruise or forest inventory. For more information on basal area, see Alabama Extension publication Basal Area of Measure Made for Management.