Creatinine clearance calculator

What is the Cockcroft-Gault equation?

An estimate of creatinine clearance published in 1976: CrCl (mL/min) = (140 − age) × weight (kg) ÷ (72 × serum creatinine in mg/dL), and 15% less for women (× 0.85).

Example

A 60-year-old man weighing 72 kg with a creatinine of 1.0 mg/dL: (140 − 60) × 72 ÷ (72 × 1.0) = 80 mL/min. A woman with the same values: 68 mL/min.

Which weight should I use?

The original study used actual body weight. For people who are overweight or obese, the FDA’s 2024 guidance notes that ideal or adjusted body weight is likely to give a more accurate estimate than actual weight.

Is creatinine clearance the same as eGFR?

No — they estimate kidney function in different ways and can give different numbers. Cockcroft-Gault is still used for many drug-dosing labels; the eGFR calculator uses the 2021 CKD-EPI equation, which labs report.

What if my creatinine is in µmol/L?

Choose µmol/L; the calculator divides by 88.4 to convert to mg/dL.

Where did the equation come from, and how well did it work?

Cockcroft and Gault built it from the relationship they found between age and 24-hour creatinine excretion per kilogram in 249 patients aged 18 to 92. They then compared its predictions, and those of four other methods, with the average of two measured 24-hour clearances in 236 patients. The correlation was 0.83, and on average the gap between predicted and measured values was no larger than the gap between two clearances measured in the same person. The formula was developed for adult men, with 15% less for women. Age and body weight, they concluded, must be included to predict clearance reasonably.

Worked example: a 70-year-old with a creatinine of 1.2 mg/dL

For a 70-year-old man weighing 60 kg: (140 − 70) × 60 = 4200. The denominator is 72 × 1.2 = 86.4. Dividing gives 48.6 mL/min. For a woman with the same age, weight and creatinine, multiply by 0.85: 41.3 mL/min. The same blood test therefore gives a lower clearance for a woman, because the equation takes 15% off.

Why does the answer differ from my lab’s eGFR?

Two things differ. The units: the CKD-EPI eGFR is scaled to 1.73 m² of body surface area, mL/min/1.73 m², while Cockcroft-Gault gives plain mL/min for your actual size, so a very large or very small person will see the two diverge. And the inputs: eGFR uses age and sex but not weight, while Cockcroft-Gault depends directly on weight. Use whichever value the drug label or your clinician asks for.

Common mistakes with creatinine clearance

Entering weight in pounds in the kilogram box: 60 kg is 132 lb, and 132 typed as kilograms returns 91 mL/min instead of 41 for the woman in the example. Typing a creatinine in µmol/L without switching the unit. Applying the formula to a child: it was derived from adults aged 18 to 92, and the calculator accepts only adults. Treating the result as a measured clearance: it is an estimate from one blood test, and drug dosing decisions belong to your clinician or pharmacist.

Sources and related calculators

Sources: D. W. Cockcroft and M. H. Gault, “Prediction of creatinine clearance from serum creatinine,” Nephron 16 (1976) 31–41; L. A. Inker et al., New England Journal of Medicine (2021), for the units of the CKD-EPI eGFR. Related: eGFR calculator, body surface area calculator, ideal weight calculator and BMI calculator.

For general information only — not medical advice. Talk with your doctor or another health professional about your own health. How we check our calculators.