Glomerular filtration rate (GFR) is an important parameter for evaluating renal function, and the common calculation methods are mainly the Cockcroft-Gault formula and the MDRD formula. The Cockcroft-Gault formula is: GFR (ml/min) = (140 – age) × weight (kg) ÷ [72 × Scr (μmol/L)]. If the patient is a woman, the above calculation is multiplied by a factor of 0.85. The MDRD formula is GFR (ml/min) = 175 × Scr -1.154 × (age) – 0.203, which is multiplied by 0.742 and 1.21 for female and black patients, respectively. Both formulas depend on the serum creatinine level and patient characteristics (age, sex, etc.), and it should be emphasized that they are only applicable when the creatinine level is stable, and that if the patient’s creatinine level fluctuates considerably, the calculated GFR may be biased. More accurate measures such as measurement of fluorescein distribution or non-invasive estimation of GFR may be required. In all cases, the determination of GFR should be performed by a medical professional to ensure accuracy and usefulness.