AIM: To correlate between CT chest severity score in COVID 19 patients with Clinical [SpO2, RR, PaO2/FiO2] and Biochemical parameters [NLR ratio, CRP, D- Dimer values]. METHODS: A Retrospective, observational study was conducted in a tertiary care hospital in Kanchipuram, Tamil Nadu. 110 patients were admitted to the hospital with COVID 19 [RT PCR swab for COVID 19 positive and radiologically positive] between March 2021 to June 2021. The patient was clinically, radiologically, and biochemically evaluated. CT chest severity score was used to differentiate the patients into mild, moderate, and severe groups. The relationship between CT Severity score and Clinical parameters such as SpO2, RR, PaO2/FiO2 and Biochemical markers [ NLR ratio, CRP, D-Dimer] were studied. RESULTS: CT chest severity score was found to be positively correlated with decreased SpO2 levels, decreased PaO2/ FiO2, increased RR and elevated NLR ratio, D Dimer and CRP levels(P < 0.001). CONCLUSION: The 25 CT Severity score scores well with the Clinical parameters and biochemical markers. Our data suggest that CT Chest Severity Score correlates well with clinical parameters and biochemical markers.