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Creatinine Clearance (Cockcroft-Gault)

Estimate creatinine clearance.

How it is calculated

The tool applies the Cockcroft-Gault equation: CrCl = (140 − age) × weight ÷ (72 × SCr), with age in years, weight in kg and serum creatinine (SCr) in mg/dL. For female patients the result is multiplied by 0.85. The answer is rounded to a whole number and shown in mL/min. It uses exactly the weight you type (it does not switch to ideal or adjusted weight), and any sex other than female is treated as male. Age must be above 0 and at most 120, and weight and creatinine must be above 0, otherwise no result appears.

Worked example

A 65-year-old woman weighing 70 kg with serum creatinine 1.2 mg/dL. First 140 − 65 = 75. Multiply by weight: 75 × 70 = 5250. The denominator is 72 × 1.2 = 86.4, so 5250 ÷ 86.4 = 60.76 mL/min. Because the patient is female, 60.76 × 0.85 = 51.65, which the tool rounds to 52 mL/min. The same inputs for a man give 61 mL/min.

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Common mistakes

  • Entering creatinine in µmol/L. The formula's constant 72 is for mg/dL; a lab value like 106 µmol/L (about 1.2 mg/dL) would give a nonsense tiny clearance.
  • Entering weight in pounds instead of kg, which inflates the result by roughly 2.2 times.
  • Forgetting to set sex to female. The 0.85 factor is skipped by default, so the female result is about 18% too high.
  • Reading the result as an eGFR. Cockcroft-Gault gives mL/min for the person's actual size, not an index normalised to 1.73 m², so the two are not interchangeable.
  • Using a creatinine from a different day than the weight and age on record, or a value taken while kidney function is changing quickly; the formula assumes a steady state.

Sources

About this calculator

This calculator estimates creatinine clearance using the Cockcroft-Gault equation: CrCl = [(140 − age) × weight] / (72 × serum creatinine), multiplied by 0.85 for female patients — a quick estimate of how well the kidneys are filtering blood, expressed in mL/min.

Clinicians, pharmacists and nursing staff use it mainly for drug dosing, since many medications are cleared by the kidneys and need dose adjustments when clearance is reduced. It's an estimate based on age, weight and a lab creatinine value, not a substitute for a measured or eGFR-based renal function test.

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Comments (1)

  • Editorial team

    This estimate uses exactly the body weight you enter. For patients much heavier or lighter than average, or who retain fluid, clinicians sometimes prefer an ideal or adjusted weight, and the tool does not switch. Cockcroft-Gault clearance in mL/min is also not interchangeable with eGFR, which is scaled to body surface area, so check which one a drug reference expects. A pharmacist can say which applies to a given medicine. Which reference or protocol do you compare this number against?

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