Glomerular Filtration Rate has conventionally been indexed to Body Surface Area (BSA). The Du Bois and Mosteller formulae are used in calculating BSA. Recently, the methodologies in GFR determination have been cited as possible sources of discrepancies. This study was done to determine if a statistically significant difference exists in the GFRs obtained using the BSA calculated by the Du Bois and the Mosteller formulae; if such differences are related to age, sex, height, weight, and BMI. A review of the GFR results obtained in our institution was done. A total of of 186 subjects were included. GFR results were normalized to BSA using the two formulae. The difference between the resulting GFRs were caculated and subjected to appropriate statistical methods to determine their relationship to age, sex, height, weight, and BMI. They were then classified into different CKD stages and observed for any shifts in classification when the formula was changed. No correlation was observed between the differences and sex (P value = 0.70). Negative correlation was noted between the differences and age, height, and weight. Individuals with normal BMIs had the smallest differences. Those that were underweight showed the biggest differences. Of the 186 subjects, 9 patients had a shift in CKD classification when the GFRs using the Du Bois formula was compared to those using the Mosteller formula. The differences between the surface-area-normalized GFRs obtained using the two formulae are statistically significant and may affect clinical decision-making, patient management, and long-term outcome.