The determination of the forming force required for manufacturing of the specified component is very important in practice. It is necessary to know value of the deformation resistance of the forming process for its theoretical finding. This paper presents a methodology for calculating of the total deformation resistance and subsequently of the forming force by using the theoretical equations. The method of the tube flaring was chosen for the research. The experiments were done on the testing tube samples from material 1.4301. These experiments were performed for comparing of the theoretical and real values of the forming force. The calculated values of forces differ slightly from those obtained experimentally. This difference lies in the use of the simplified input conditions and computational analysis such as material model obtained from tensile test of tubes, the chosen coefficient of friction and the simplified approach to calculation of the bending stress used in the theory of deep drawing.