In this study, five error evaluation functions are used to calculate the error deviation between the experimental data and the predicted data for Maxsorb III/ethanol and RD silica gel/water pairs when the isotherm data fitted with six isotherm models. An error analysis based on the sum of normalized error (SNE) is performed to observe the effect of different error evaluation functions for the determination of isotherm parameters. On the basis of error values, Tòth isotherm provides less error compared to other models for both pairs. Error analysis using SNE advocates that HYBRID error evaluation function is suitable for DA, Freundlich, and Hill models for both pairs whereas ARED error evaluation function is appropriate for Tòth and Langmuir models for Maxsorb III/ethanol pairs. However, RMSD for Redlich-Peterson and SSE for Tòth are appropriate for Maxsorb III/ethanol and silica gel/water pairs, respectively. Seven statistical tools are employed to predict the best isotherm model for the studied pairs. It is found that, except F-test, all other functions provide agreeable results for the better fitting of Tòth model for Maxsorb III/ethanol pair. More or less, similar findings are observed for the RD silica gel/water pair. Moreover, seven information criteria (IC’s) are also performed in order to find the optimum isotherm model. On the basis of IC’s, Tòth model provides less information loss compared to other models for the studied pairs.