BACKGROUND : Surgical margin is one of the most important prognostic factors in oral cavity squamous cell carcinoma. There have been studies which refute the standard practice of considering 5 mm (mm) margin as free. Therefore we aimed to evaluate the impact of each mm of margin on the local recurrence free survival (LRFS) and to obtain a cut-off value which would impact the survival the most. METHODS : This was a retrospective study of 602 treatment naïve patients of buccoalveolar complex cancer. ROC curve was plotted for each millimetre of margin to derive the cut-off margin for maximum LRFS. Multivariate analysis was done for the margin groups to calculate the margin beyond which no significant improvement on LRFS was achieved. Early and advanced tumors were also evaluated separately. RESULTS : A cut off margin of 5.5 mm was achieved on ROC for early (T1-T2) tumors and 6.5 mm cut off was achieved for advanced (T3-T4) tumors. Based on these cut off different margin groups were made. The cohort was grouped into positive margin, 1-5.5 mm, 5.6-7 mm and > 7 mm. Hazard ratio for patients with 1-5.5 mm and positive margin was 1.886 (95%CI, 1.15 to 3.09) and 5.58 (95%CI, 1.75 to 17.78) respectively. HR for margin 5.5 mm to 7 mm was 1.15 (95% CI, 1.15 to 2.06). There was no statistically significant difference in survival between margin groups of 5.6-7 mm and > 7 mm (p < 0.589) for both early and advanced tumors. CONCLUSIONS : Minimum surgical margins of 5.5 mm in the final histopathology should be aimed for in the bucco-alveolar carcinomas. There was significant improvement in LRFS with increasing margins upto 7 mm. Taking margins beyond 7 mm does not improve LRFS.