Reliable efficiency calculation of high-subsonic and transonic compressor stages requires a detailed and accurate prediction of the flow field within these stages. Despite the tremendous progress in turbomachinery computational fluid mechanics, the compressor designer still uses different loss correlations to estimate the total pressure losses and thus the efficiency of the compressor stage. A new loss model is presented in this article. Special attention is paid to the shock and profile losses, since they contribute significantly to the total pressure loss balance, specifically for transonic compressor stages. A new shock loss model is presented that calculates the shock position and the shock total pressure losses. The available experimental data were used to establish new loss correlations that account for experimental findings.