We have investigated the surface plasmon resonance (SPR) phase change across a range of excitation wavelengths (i.e. spectral-phase) using the Fresnel's equations and Transfer Matrix technique with emphasis on optimizing refractive index sensing performance. Having evaluated the phase change characteristics upon varying different sets of parameters, our results indicate the possibility of achieving extremely high resolution within a wide range of sample refractive index (1.3330–1.3505) at a fixed angle of incidence. We also demonstrate that the double-layer (silver/gold or copper/gold) configuration holds very promising characteristics for SPR sensing, and it is possible to achieve a detection limit of 7.9×10−9 RIU (refractive index unit) if one uses a phase measurement resolution of 2×10−4 rad. Among all the factors, material of the metal film and its thickness are found to affect performance most. This work provides a comprehensive analysis of the interplay between various system parameters.