Introduction:-Cataract surgery is a major cause of reversible blindness worldwide, with the primary goal of restoring vision and achieving optimal refractive outcomes. Advancements in surgical techniques and intraocular lens (IOL) technology have shifted focus towards refining the accuracy of post-surgery refractive outcomes. The precise calculation of IOL power pre-operatively is crucial for determining the refractive status of the eye post-surgery. The success of cataract surgery is not solely dependent on the removal of the cataract and the implantation of the IOL. The refractive outcome is largely influenced by the accuracy of the IOL power calculation performed before the surgery. Formulas have evolved over the years to improve the accuracy of IOL power calculations, but achieving accurate refractive outcomes remains a challenge, particularly in eyes with extreme axial lengths or other unusual anatomical features. This study aims to evaluate refractive errors observed in post-operative cataract patients and correlate these errors with the pre-operative IOL power calculated using various formulas. Material and Methods:- This study was conducted at a tertiary care hospital in Rajkot from 2023 to 2024, involving 300 patients who visited the Outpatient Department for cataract surgery. The research aimed to compare the accuracy of five IOL power calculation formulas using the A Scan machine. Patients were selected based on their attendance at the OPD and evaluated for various ocular parameters. The study included patients with visually significant cataracts, primary implantation of posterior chamber intraocular lens, and willingness for participation. Patients with co-existing pathology, combined cataract surgery, previous intraocular or corneal surgery, corneal astigmatism greater than 1.5 D, traumatic cataract, uveitic cataract, pediatric cataract, corneal opacity, intraoperative complications, and other ocular pathology causing visual impairment were excluded. All patients underwent a comprehensive ophthalmic examination, including preoperative A scan biometry, postoperative autorefraction, and slit lamp evaluation. The mean absolute error (MAE) was calculated and compared in three groups of axial length. Results:- The study analyzed the refractive outcomes of cataract surgery in 300 participants, focusing on the accuracy of various IOL power calculation formulas. The participants were divided into three groups based on axial length: Group I (< 22 mm), Group II (22 to 24 mm), and Group III (> 24 mm). The HOLLADAY-II formula consistently provided the most accurate predictions across all axial length groups, while the BINKHORST-II formula had the highest error. The SRK-T and HOLLADAY-II formulas performed best in Group I, Group II, and Group III, with the HOLLADAY-II formula being the most reliable, producing the smallest postoperative refractive errors, particularly in average and long axial lengths. Conclusions:-The study emphasizes the importance of choosing the right IOL power calculation formula based on a patient's axial length. The HOLLADAY-II formula is the most accurate, while the SRK-T formula is reliable for average axial lengths. Preoperative planning and patient counseling are crucial for optimal refractive outcomes.