Creatinine Clearance Calculator

Use this Creatinine Clearance Calculator to estimate creatinine clearance (CrCl) with the Cockcroft–Gault equation using age, sex, body weight, and serum creatinine.

Medical warning: This result is an estimate only. Do not use it by itself to diagnose kidney disease or to start, stop, or change medication doses. Kidney-function and drug-dosing decisions should be confirmed with a qualified clinician or pharmacist and the current prescribing information for the medication.

Cockcroft–Gault Formula

For males:

CrCl = [(140 − age) × weight in kg] ÷ (72 × serum creatinine in mg/dL)

For females, the original Cockcroft–Gault equation applies a historical adjustment:

CrCl = male-equation result × 0.85

The result is expressed in:

mL/min

Worked Example

Suppose a male patient is:

• 65 years old
• 180 lb
• Serum creatinine: 1.2 mg/dL
• Actual body weight selected

Convert weight:

180 ÷ 2.20462 ≈ 81.65 kg

Apply the equation:

CrCl = [(140 − 65) × 81.65] ÷ (72 × 1.2)

CrCl ≈ 70.9 mL/min

This is an estimated creatinine clearance, not a measured GFR or a diagnosis of kidney function.

Body Weight Selection

Body weight is part of the Cockcroft–Gault equation, so the selected weight method can materially affect the result.

The calculator can display actual, ideal, and adjusted body-weight options. These are clinical adaptations used differently across institutions and patient populations; there is no single weight-selection rule that is appropriate in every case.

Use the body-weight method required by the relevant clinical protocol, pharmacist, clinician, or medication guidance.

Creatinine Clearance vs. eGFR

Cockcroft–Gault creatinine clearance and laboratory-reported estimated glomerular filtration rate (eGFR) are different estimates.

• CrCl: historically used in many medication-dosing studies and drug labels.
• eGFR: commonly used for modern assessment and classification of kidney filtration function.

Do not apply eGFR chronic-kidney-disease staging categories directly to a Cockcroft–Gault CrCl result.

Current National Kidney Foundation guidance advocates greater use of race-agnostic eGFR for medication-related decisions, while some drug prescribing information still specifies creatinine clearance. Follow the equation and cutoff required for the specific medication and clinical situation.

Important Limitations

• The equation is most appropriate when serum creatinine is relatively stable.
• Results may be unreliable during acute kidney injury or rapidly changing kidney function.
• Very low or high muscle mass, amputation, malnutrition, severe illness, edema, and unusual body composition can reduce accuracy.
• The original equation was developed decades ago using older creatinine assays and a limited study population.
• The historical 0.85 female adjustment was estimated in the original work rather than derived from a comparable female development cohort.
• Modern serum creatinine assays and current patient populations differ from those used to create the original equation.
• Medication dosing may depend on the specific drug label, indication, patient characteristics, dialysis status, and other clinical factors.

Sources

• Cockcroft & Gault — Prediction of Creatinine Clearance From Serum Creatinine
• National Kidney Foundation — Cockcroft–Gault Equation and Current Limitations
• U.S. FDA — Renal Impairment and Medication Dosing Guidance