Computer aided procedure for design of distribution transformer is implemented on transformer type ETN 50-1-/0.4 a product of “EMO” company. All transformer parameters are calculated in Matlab as well as operational characteristics of voltage variation and efficiency factor at different type of loads and variation of secondary voltage for different secondary currents. The obtained results are compared to the experimental data from the producer. Finite Element Method (FEM) is implemented for calculation of distribution of magnetic flux density in transformer cross section for different operating regimes: no-load and rated load. FEM calculations are based on data obtained from transformer design. They enable electromagnetic processes inside the machine to be analyzed and accurate calculation of magnetic flux density to be done.