Glomerular filtration rate (GFR) is the best overall index of kidney function. Normal GFR varies according to age, sex, and body size, and declines with age.
Software use Cockcroft-Gault (for GFR) and the DuBois formula (for BSA) to show value in mL/min/1.73m2. It be recommend by NKF's KDOQI clinical practice guidelines to estimate GFR.