Introduction: The diameter of the quadrupled Hamstring graft plays a significant role in the incidence of graft failures for ACL reconstruction. The ability to predict the graft size pre-operatively can prepare the surgeon for alternatives in the event of an inadequate graft diameter. Materials and methods: We retrospectively measured the diameter of the Semitendinosus tendon (ST) on the MRI in all patients who underwent arthroscopic ACL reconstruction using quadrupled Semitendinosus as their graft. We also estimated any correlation between various anthropometric data with pre-operative MRI based Cross Sectional Area (CSA) of the Hamstring tendon and final graft diameter in the South Asian population. The patients were included from Jan 2018 - Dec 2020. Results: The minimum CSA of ST to predict an eventual graft diameter of 7.5mm was 10.7mm2 . The MRI based cross-sectional area measurement showed moderate correlation with the intra-operative graft diameter obtained. (r=0.62, p<0.001). The intra-class correlation coefficient between the radiologist and the surgeon was 0.82, 95% CI (0.57, 0.92) and a p-value <0.001. Conclusion: Pre-operative MRI can be a useful tool to predict the graft diameter. This coupled with the anthropometric data of the patient can be used as an adjunct to estimate the probable graft diameter. Thus, the surgeon can be better prepared for the surgery and can seek alternate graft options if the graft size is deemed inadequate preoperatively.