A method and a system for obtaining optimal range of values for real estate property by using all or some of the admissible appraisal approaches through optimization algorithm. The reliability of factor ranges specific to each appraisal approach is evaluated and discrepant ranges are eliminated. An accurate property valuation through a number of admissible appraisal approaches is possible. Valuation, Feasibility Study, Sensitivity Analysis, value reconciliation and highest and best use are obtained optimally and automatically. Capitalization rate and period are optimized in the relevant approaches.