Gas turbines are likely to face critical situations such as compressor surge and stall in the sub-idle operation region. Thus, it is important to predict the operation characteristics of gas turbines accurately by using simulations in the sub-idle region. However, sufficient information about the component performance maps in the sub-idle region is generally not available, and extrapolation methods are usually used to generate data. However, extrapolation methods tend to generate physically invalid data points in very low-speed regimes, which sometimes cause critical numerical problems in simulations of engine performance. This study proposes a new method to generate performance data in the sub-idle region of turbine performance maps through interpolation. A zero point is introduced where the pressure ratio is one and the mass flow rate is zero. Performance data were generated between the existing performance curve and the zero point using the interpolation. To validate the proposed method, it was applied to publicly available turbine performance maps. It was confirmed that the proposed method improves the numerical matching between the compressor and turbine maps and thus expands the predictable operating regime by as much as 23.3% compared to a conventional extrapolation method. (C) 2019 Elsevier Ltd. All rights reserved.