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Cockcroft–Gault Calculator

Estimate creatinine clearance (CrCl).

How it is calculated

The tool applies CrCl = (140 − age) × weight ÷ (72 × SCr), with age in years, weight in kilograms and serum creatinine (SCr) in mg/dL. It always shows two results: the value as written, labelled male, and the same value multiplied by 0.85, labelled female. There is no sex selector, so you read the line that applies. Age, weight and creatinine must all be above zero, and age must be below 140. The result is in mL/min and rounded to two decimals. The formula uses the weight you enter as it is: it does not adjust for obesity, oedema or very low muscle mass, and it is an estimate to support a clinician, not a diagnosis or a dosing instruction.

Worked example

A 65-year-old weighing 72 kg has a serum creatinine of 1.2 mg/dL. Step 1: 140 − 65 = 75. Step 2: 75 × 72 = 5,400. Step 3: 72 × 1.2 = 86.4. Step 4: 5,400 ÷ 86.4 = 62.50 mL/min for a man. Step 5: for a woman multiply by 0.85, which gives 53.13 mL/min.

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Common mistakes

  • Reading the male line for a female patient, which overstates clearance by about 18%.
  • Entering creatinine in µmol/L; the formula needs mg/dL, and µmol/L divided by 88.4 gives mg/dL.
  • Entering weight in pounds instead of kilograms.
  • Treating the result as a normalised eGFR: Cockcroft–Gault gives clearance in mL/min, not per 1.73 m² of body surface.
  • Using it as it stands when creatinine is changing quickly, such as in acute kidney injury, where a single value does not reflect true filtration.

About this calculator

The Cockcroft–Gault equation estimates creatinine clearance (CrCl), a proxy for kidney filtration rate, as CrCl = [(140 − age) × weight] / (72 × serum creatinine), multiplied by 0.85 for female patients (age in years, weight in kg, serum creatinine in mg/dL). Unlike the newer eGFR formulas, Cockcroft–Gault uses actual body weight and was specifically validated for adjusting drug doses, which is why it remains the reference method in many drug-dosing guidelines even though other formulas are considered more accurate for diagnosing kidney disease.

Physicians and hospital pharmacists use it to adjust doses of renally-cleared medications (such as certain antibiotics, anticoagulants, and chemotherapy agents) to avoid toxic accumulation in patients with reduced kidney function, nephrologists use it alongside other renal function markers, and nursing and pharmacy students learn it as a standard formula in clinical pharmacology coursework.

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