The problem of determining the operating modes of steam turbine stages in low-steam and motor modes (MM) is considered. The analysis and generalization of existing methods for estimating losses on heating and ventilation in steam turbines is given, the possibility of their application in the motor mode is considered, and a new technique is proposed that takes into account the peculiarities of the hydrodynamic processes occurring in the active stages of a steam turbine in steamless, low-steam and motor modes. It is shown that the uncertainty of calculating friction and ventilation losses and considering the importance of the value of these losses in modeling the temperature state of steam turbine stages when they operate in steamless and motor modes, the need to develop a methodology for estimating these losses, taking into account the features of these modes, is an urgent. To assess the totality of power losses for friction and ventilation in the motor mode, a calculation technique is proposed, which is based on the condition that the stage goes into ventilation mode when the heat transfer on the stage is less than its minimum value for power generation. Based on this condition, calculation formulas are obtained that will allow calculating the totality of friction and ventilation losses in the steam turbine stages and in the turbine as a whole during the operation of the steam turbine in MM with known: geometric parameters of the stage; steam pressure distribution along the flow part of the turbine; steam consumption through the steps.