Cockcroft-Gault formula is used to estimate creatinine clearance rate using age, weight and serum creatinine level. It is named after the scientists who created the formula.
(140-age) * Weight (in kilograms) * 0.85 (if patient is female)
72 * Serum creatine (in mg/dl)
Hence, the creatine clearance will be less in elderly individuals and females.