Purpose: Necrotizing fasciitis is the rapidly progressive inflammation of fascia, with necrosis of subcutaneous tissues and subsequent high morbidity and even mortality. Neutrophil to Lymphocyte Ratio, Systemic Immune-inflammation Index and Platelet to Lymphocyte Ratio are recently being used as severity indicators in inflammatory conditions. This study attempted to find the usefulness of these three ratios as predictors of amputation in necrotizing fasciitis.Methods: This was a cross sectional study in a tertiary level teaching institution in South India, from January 2018 until January 2019. 175 patients with clinical diagnosis of Necrotizing Fasciitis were studied and data analysed to find out the diagnostic accuracy of relevant study parameters. Results: 13 out of the 175 patients had to undergo amputation. Diabetes mellitus, infection with Klebsiella and E.coli, low serum albumin and high blood glucose were found to be the most common factors associated with amputation. Neutrophil to Lymphocyte Ratio had acceptable sensitivity and very good specificity. Neutrophil to Lymphocyte Ratio also had an area under curve of 0.726. Multivariate logistic regression revealed Neutrophil to Lymphocyte Ratio to be the primary hazard factor with an Odds Ratio of 9.64.Conclusion: Neutrophil to Lymphocyte Ratio and to some extent Platelet to Lymphocyte Ratio and Systemic Immune-inflammation Index are good predictors of amputation in patients with Necrotizing fasciitis. These simple and easily available laboratory tests can be included in the diagnostic panel for these patients and to titrate the treatment.