We present the ionospheric response of ge-omagnetic storms as observed from ionospheric Total Electron Content (TEC). We select nine storm events and study the GPS-TEC profiles observed from two IGS stations, IISC, Bangalore, India, and AUCK, Auckland, New Zealand. We try to estimate the TEC profiles numerically by using the empirical orthogonal function (EOF) and SSM-T1 (nonlinear regression analysis) approaches. We choose the geomagnetic storms satisfying the condition of Dst ≤ 50 nT and Kp ≥ 50. The F10.7 and Ap indices are chosen as inputs for the EOF modelling approaches to account for geomagnetic activity. The SSM-T1 model is composed of three components: diurnal, seasonal, and solar dependence fluctuations associated with VTEC data, and is fitted using the nonlinear least-squares technique using a total of 18 coefficients. The EOF and SSM-T1 models are built and tested on different storms using GPS TEC data for storm days from 2009 to 2017. The EOF and SSM-T1 models perform well for storms with non-significant ionospheric TEC responses. The EOF-TEC model reasonably estimates the night and early morning TEC well, but it does not reproduce short-term characteristics. Significant enhancement and depression in TEC are estimated by SSM-T1 better than in the EOF model. The storm enhancements in GPS-TEC are observed for both stations. The maximum enhancement in VTEC for IISC is observed for the storm in 2013, and the same for AUCK is observed in 2011. Positive and negative storm effects are observed in low and mid-latitude stations. The reduction or enhancement in the thermo-ionospheric [O/N 2 ] ratio plays a significant role in the decrement or enhancement in TEC during the storm.