Water saturation parameter is one of the most important petrophysical parameters in hydrocarbon reservoirs evaluation and fluid in-place calculation. Thus, estimation of the water saturation is an essential task in the evaluation of the formation. The calculation of water saturation is commonly linked to the so-called Archie equation, and hence, the accuracy of estimation depends on the accuracy of the Archie’s parameters. Archie obtained these coefficients for clean sandstones and provided constant numbers for this lithology. The role of cementation factor (m), as one of the intervening parameters, is very significant in this way, so that a small change in this coefficient causes considerable changes in water saturation. Unlike sandstones, carbonate rocks have a great heterogeneity and variety in lithology, and the value of m does indeed depend on the amount and type of porosity, permeability, rock texture, salinity of water formation and others. In addition, the presence of clay in the rock changes the petrophysical and electrical properties by changing the pore volume and creating an electrical conduction path. Given the dependence of the cementation coefficient on the petrophysical and electrical properties, the assumption that it is constant does not seem to be logical. In this study, the electrical quality index (EQI*) is used to classify rocks based on electrical properties to estimate the cementation coefficient in rocks containing clay. This method was applied to 204 clay containing rock samples from different wells in several different basins in the western United States. Formation strength coefficient (F*) has been used for these rocks calculated by Waxman-Smits model. The use of EQI* technique led to the division of samples into 9 different groups that have different equations of formation resistivity factor and cementation factor against porosity. By linear fitting of the data on the log-log plot of F* versus porosity, the value of cementation factor of