SI units
Creatinine clearance (mL/min) = 1.23 * Weight (kg) * (140 - Age (y)) / Creatinine (micromol/L)
Mass units
Creatinine clearance (mL/min) = Weight (kg) * (140 - Age (y)) / Creatinine (mg/dL) * 72
Valid for ages 18 - 92 years.
Normal values are 120 (males) or 95 (females) +/- 20 mL/minute.
Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron 1976;16(1):31-41