Current issue: 51(4)
Under compilation: 51(5)
Because the cross-sectional area of a tree stem is ellipsis, it cannot be determined exactly with only the diameter measurement. The article presents a formula and the calculation of the exact cross-sectional area. If the cross-sectional area is calculated as arithmetic mean of two diameter measurement, varies the error between two limit values. The error becomes smallest by calculating the area based on the biggest and the smallest diameter measurements.