Creatinine Clearance Calculator (Cockcroft-Gault)
Estimate creatinine clearance with the Cockcroft-Gault equation using actual, ideal or adjusted body weight, creatinine in mg/dL or µmol/L, with BMI-based weight guidance and kidney function ranges.
How it works
CrCl (mL/min) = ((140 − age) × weight kg) ÷ (72 × creatinine mg/dL) × 0.85 if female · creatinine mg/dL = µmol/L ÷ 88.4 · IBW = 50 kg (men) or 45.5 kg (women) + 2.3 kg per inch over 5 ft · AdjBW = IBW + 0.4 × (actual − IBW)
The Cockcroft-Gault equation estimates creatinine clearance, a stand-in for how well the kidneys filter, from age, weight, sex and serum creatinine. It is not normalized to body surface area. It is still widely used for drug dosing, because most renal-dosing tables and package inserts were built on it. Creatinine can be entered in mg/dL or in µmol/L (divided by 88.4). Which weight to use matters: actual body weight overestimates clearance in obesity, and ideal body weight overestimates it in someone who weighs less than ideal. With a height, the calculator works out ideal body weight with the Devine formula (50 kg for men, 45.5 kg for women, plus 2.3 kg per inch over 5 ft) and adjusted body weight (ideal plus 40% of the excess). It then shows the clearance with each weight. The By BMI option follows the rule used by MDCalc and Omni: actual weight when underweight, ideal weight at a normal BMI (or actual weight if it is lower), and adjusted weight at a BMI of 25 or more. The result is placed on the KDIGO GFR scale for context only. CKD stages come from an eGFR equation plus albuminuria. The equation assumes a stable creatinine and does not apply in acute kidney injury.
Worked example
A 55-year-old man weighing 80 kg with serum creatinine 1.0 mg/dL (88 µmol/L): CrCl = ((140 − 55) × 80) ÷ (72 × 1.0) = 6,800 ÷ 72 ≈ 94.4 mL/min with actual weight. For an otherwise identical woman, multiplying by 0.85 gives about 80.3 mL/min. Omni’s worked example, a 67-year-old man of 92 kg and 173 cm with creatinine 1.4 mg/dL, has a BMI of 30.7. His ideal weight is 50 + 2.3 × (68.1 − 60) = 68.7 kg and his adjusted weight is 68.7 + 0.4 × (92 − 68.7) = 78.0 kg, so CrCl = (73 × 78.0) ÷ 100.8 ≈ 56.5 mL/min, against 66.6 mL/min with actual weight.
Sources: Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron 1976;16:31–41 · MDCalc — Creatinine Clearance (Cockcroft-Gault Equation) · KDIGO 2024 Clinical Practice Guideline for CKD (GFR categories) · FDA — Pharmacokinetics in patients with impaired renal function (guidance) · Cockcroft-Gault equation
Frequently asked questions
How does Cockcroft-Gault differ from eGFR?
Cockcroft-Gault estimates creatinine clearance in mL/min and includes body weight. CKD-EPI eGFR is normalized to 1.73 m² of body surface and does not use weight. Drug-dosing references were largely built on Cockcroft-Gault, so it is still preferred for that purpose, while eGFR is used to diagnose and stage chronic kidney disease.
Which weight should I use?
Follow the dosing reference you are working from. Many hospital protocols use actual weight if the person weighs less than ideal, ideal weight at a normal BMI, and adjusted weight (ideal + 0.4 × excess) with overweight or obesity. Choose By BMI to apply that rule, or compare all three in the table.
How do I convert creatinine from µmol/L to mg/dL?
Divide by 88.4. For example, 106 µmol/L ÷ 88.4 = 1.20 mg/dL. You can also pick µmol/L in the unit menu next to the creatinine field, and the calculator converts it for you.
Should a low creatinine be rounded up to 1.0?
Some clinicians round creatinine up to 0.8 or 1.0 mg/dL in frail older adults, because a very low value from low muscle mass can make the estimate too high. Studies show rounding often underestimates clearance instead, so it is not a universal rule. This calculator uses the value you enter. Follow your institution’s protocol.
When is the estimate unreliable?
It assumes steady-state kidney function, so it is inaccurate during acute kidney injury or when creatinine is changing quickly. It is also unreliable at extremes of muscle mass or body size, in pregnancy, in amputees, and in people on dialysis. A measured 24-hour urine creatinine clearance is more accurate in those cases.
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Educational estimate using standard published formulas — not medical advice, a diagnosis, or a substitute for clinical judgement. Dosing, diagnosis and treatment must be decided by a qualified clinician using validated tools and the full clinical picture.