Spark plasma sintering (SPS) has gained considerable attention as a manufacturing method that enables rapid powder densification through the simultaneous application of electric current and pressure. Despite recent advances in numerical modeling to understand and optimize the complex multiphysics phenomena during sintering, accurate prediction of sintering behavior remains challenging due to the reliance on different constitutive equations and their porosity-related parameters. This study presents a two-step methodology that combines direct experimental measurements with numerical simulations to improve the comprehensiveness and reliability of material parameter identification in SPS. The approach involves the development of a finite element-based, fully coupled electrical-thermo-mechanical model, which is then validated by experimental testing. The parameter identification process demonstrates an average density prediction error of less than 1.5% when applied to copper and nickel SPS under varying heating rates (25 to 100 K/min). This framework ensures improved density prediction throughout the SPS process and improves model adaptability for different materials. Importantly, it eliminates the need to determine material parameters separately for each heating rate, providing generality that is critical for computational models that are affected by the heating rate of the sintering process.