India is among the world's most seismically active nations, making robust earthquake-resistant design a critical imperative. The newly published IS 1893:2025 (Part 1 and Part 5) introduces sweeping revisions over IS 1893:2016, most notably a paradigm shift from Deterministic Earthquake Hazard Assessment (DEHA) to Probabilistic Earthquake Hazard Assessment (PEHA). Consequent changes include updated seismic zone maps with the introduction of Zone VI, revised peak ground acceleration values, refined design spectra extending to 10 seconds, probabilistic return-period-based structural importance classification, shear-wave-velocity-based soil site classification, and new provisions for Architectural Elements and Utilities (AEUs). This paper presents a systematic comparative study of IS 1893:2016 and IS 1893:2025 provisions applied to low-rise (G+6), mid-rise (G+14), and high-rise (G+19) reinforced concrete (RC) building models in Seismic Zone III/IV (Vadodara and Ahmedabad, India). All models are analyzed using ETABS v22.5.0 employing the Response Spectrum Method. Key seismic response parameters—base shear, story displacement, story drift ratio, and story shear—are extracted and compared. Results demonstrate that IS 1893:2025 yields base shear increases of 149–177%, maximum displacement increases of 123–184%, and maximum story drift increases of 126–192% relative to IS 1893:2016 for the same structural systems. The paper also presents torsion checks, mass irregularity checks, and soft story checks as mandated by IS 1893 (Part 5):2025. The findings underline that the 2025 provisions lead to significantly more conservative—and structurally safer—design outcomes, and have direct implications for design economy, reinforcement detailing, and the retrofitting of existing stock.

Keywords — IS 1893:2025; IS 1893:2016; Seismic Code Comparison; Probabilistic Seismic Hazard Assessment; Base Shear; Story Drift; ETABS; RC Buildings; Response Spectrum Method; Zone Factor.