The specifications of a steam turbine need to be considered, especially the isentropic efficiency (ηt) and turbine work (Wt) specifications, concerning the operational capability of the steam turbine at the ABC Power Plant (PLTU). This study aimed to determine the values of isentropic efficiency and turbine work, using data parameters such as mass flow rate (ṁ), inlet pressure (P1), outlet pressure (P2), inlet temperature (T1), and outlet temperature (T2), utilizing the ChemicalLogic SteamTab application. The research results revealed that the specified isentropic efficiency of the turbine is 67.31%, and the turbine work is 52,438 kW. The average value of the operational isentropic efficiency during the 2-hour research period was found to be 67.74%. Likewise, the average value of the operational turbine work was determined to be 53,487 kW. It was observed that the isentropic efficiency at operational conditions was better than the specified value. This improvement in isentropic efficiency can be attributed to higher main steam temperature and lower exhaust turbine pressure values.