INTRODUCTION:Human coronavirus hadstarted its widespread pandemic from the year of 2019. Although, molecular analysis are used for diagnosis,Computed Tomography (CT) of chest,had played a major role in assessing the severity of COVID-19. AIM:To evaluate the effectiveness of CT 40 point and CT 25point severity scoring (CT-SS) systems in correlation with oxygen saturation. MATERIALS AND METHODS:A total of 395 patients COVID-19 patients with CT chest imaging were included. The CT-40 SSdependsupon parenchymal opacification. Scores of 0, 1, and 2 were given for which parenchymal opacification involved were 0%, < 50% and ≥ 50% respectively. Score of 1-12 is mild; Score of 13-19 is moderate; Score >20 is severe. The CT-25SSdependsupon lobar involvement. i.e., ≤ 5% - Score 1, 5%-25% - Score 2, 26%-50% -Score 3, 51-75% - Score 4,>75% - Score 5.Mild is ≤ 7, Moderate is 8-17, Severe is ≥ 18. ANALYSIS AND RESULTS:The spearman correlation co-efficient for CT-40 SS and CT-25 SS was found to be r =-0.7636 and r = -0.6665 respectively, based on the r value CT-40 SS is better than CT-25 SS. Increase in CT-SS results in decreased O2 saturation. The sensitivity and specificity of CT40 SS in correlation to O2 saturation was found to be 88% and 78% respectively with area under ROC curve of 0.885. The sensitivity and specificity of CT 25 SS in correlation to O2 saturation was found to be 79% and 80% respectively with area under ROC curve of 0.912.