ABSTRACT BACKGROUND Despite many clear benefits of active lifestyle lack of physical activity are common mostly among students, which further lead to alteration in body compositions. This alteration in body composition is the leading cause of various diseases as well as decrease in Fitness Index level. OBJECTIVE To correlate the body compositions i.e. Body Mass Index, Waist-to-Hip Ratio, Waist-to-Height Ratio, Neck Circumference with Fitness Index using Harvard Step Test among students of PEWS Group of Institutions and also to find which body composition is the strongest predictor of Fitness Index. METHODOLOGY 100 subjects were selected randomly in the study and were divided into two groups i.e Group A (Male) and Group B (Female), each having 50 subjects. For each subject BMI, WHR, WHtR, NC was measured. Harvard Step Test was performed and FI was calculated using it. RESULT Based on the statistical analysis i.e Karl Pearson’s Coefficient of Correlation, BMI, WHR, WHtR, NC all are negatively correlated with FI for both males and females. BMI, WHtR, NC of females and WHR of males have greater negative correlation with FI. CONCLUSION There is correlation between body compositions i.e. BMI, WHR, WHtR, NC and FI. BMI is the best predictor of FI in both males and females; also it has been observed that the males are fitter than the females.