Results of previous research studies have presented racial difference as a function of body size. Several literatures on racial variation of heart sizes also abound. This research is aimed at determining the relationships of the various indices of body size with the different indices of heart size in a Nigerian population. 1885 male and female Nigerians of ages 4 to 80 years after physical examinations were enrolled for the study. Their PA chest radiographs were obtained. Weight, height, BMI, and BSA, showed various levels of statistically significant correlation with cardiothoracic ratio; CTR, heart and chest diameters. The research presents use of heart diameter over use of CTR in predicting heart size using body size. Amongst all the indices of body size, BSA has been presented to be the strongest predictor of heart diameter followed by weight.