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Clinical calculator
Creatinine clearance calculator (Cockcroft-Gault)
Estimates creatinine clearance (CrCl, mL/min) from age, sex, weight and serum creatinine with the Cockcroft-Gault equation (1976). With a height, it also shows the result with ideal and adjusted body weight.
Creatinine clearance (Cockcroft-Gault)
When this estimate is not valid
- Unstable kidney function (acute kidney injury or a rapidly changing creatinine): creatinine-based estimates lag behind the true value.
- Dialysis or other kidney replacement therapy: these equations do not apply.
- Very high or very low muscle mass (cachexia, frailty, paraplegia, bodybuilding, malnutrition) or an unusual diet (high meat or creatine intake, vegetarian diet).
- Limb amputation.
- Pregnancy.
- Cockcroft-Gault estimates creatinine clearance in mL/min, not GFR, and is not indexed to body surface area. It was derived in 1976 in 249 adults, almost all men, with stable kidney function.
- Not for people under 18 years; paediatric equations (for example bedside Schwartz) apply.
- Today's standardised (IDMS) creatinine assays read lower than the assays of 1976, so CrCl may be overestimated. Many drug labels still use Cockcroft-Gault cut-offs.
Estimate only. Interpret it with the patient's clinical picture and the product label.
How it is calculated
CrCl (mL/min) = (140 − age) × weight (kg) ÷ (72 × SCr in mg/dL)
The Cockcroft-Gault equation, multiplied by 0.85 for women. Serum creatinine (SCr) in µmol/L is divided by 88.4 first.
IBW = 50 (men) or 45.5 (women) + 2.3 × (height in inches − 60) · AdjBW = IBW + 0.4 × (actual weight − IBW)
Ideal body weight (IBW, Devine) is 50 kg for men or 45.5 kg for women, plus 2.3 kg for every inch of height over 60 inches. Adjusted body weight (AdjBW) lies 40% of the way from IBW to actual weight.
Default weight: actual weight when it is below IBW; IBW when actual weight is 100–120% of IBW; AdjBW when it is over 120% of IBW or the BMI is 30 or more. Under 152.4 cm (5 ft) the Devine IBW is not validated, so actual weight is used. This rule is common pharmacy practice, not part of Cockcroft and Gault's paper. You can choose another weight, and some drug labels or protocols name a specific one.
Serum creatinine is used as entered. A value below 0.8 mg/dL is not rounded up; a note says the estimate may be high.
The result is shown to one decimal. Limits: age 18–110 years, weight 30–300 kg, height 120–230 cm, creatinine 0.2–20 mg/dL.
Worked example
A 70-year-old man, 70 kg, serum creatinine 1.2 mg/dL, no height entered:
(140 − 70) × 70 ÷ (72 × 1.2) = 56.7 mL/min
Estimated CrCl 56.7 mL/min.
A 70-year-old woman with the same weight and creatinine:
(140 − 70) × 70 ÷ (72 × 1.2) × 0.85 = 48.2 mL/min
Estimated CrCl 48.2 mL/min.
Questions
What is the difference between CrCl and eGFR?
Cockcroft-Gault estimates creatinine clearance in mL/min for the patient's own body size. CKD-EPI 2021 estimates GFR in mL/min/1.73 m², indexed to a standard body surface area, and is used to stage chronic kidney disease. Many drug labels give renal dose adjustments as Cockcroft-Gault CrCl cut-offs; others use eGFR. Use the measure that the product label names.
Which body weight should I use?
Cockcroft and Gault derived the equation in adult men using actual body weight. In obesity, actual weight can overestimate CrCl, so adjusted body weight is often used; below ideal weight, actual weight is used. The calculator shows all three results, applies a common default rule and lets you choose another weight. If the drug label or your local protocol names a weight, use that one.
Why is a low creatinine not rounded up?
Some protocols round a serum creatinine below 0.8 or 1.0 mg/dL up to that value in older or frail patients, because low muscle mass lowers creatinine and can make CrCl look high. Practice varies and the rounding is not part of the equation, so the calculator uses the value as entered and shows a note when it is below 0.8 mg/dL.
Can I enter creatinine in µmol/L, weight in pounds or height in inches?
Yes. Choose the unit next to each field. Creatinine in µmol/L is divided by 88.4, pounds are converted at 0.45359237 kg and inches at 2.54 cm before the equation is applied, and each conversion is shown in the arithmetic.
When is Cockcroft-Gault not valid?
It was derived in adults with stable kidney function. It does not apply during dialysis, and with acute kidney injury or a rapidly changing creatinine every creatinine-based estimate lags behind the true kidney function. Very high or low muscle mass, limb amputation and pregnancy also make it unreliable.
References
- Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron. 1976;16(1):31–41. DOI 10.1159/000180580 PubMed 1244564
- Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm. 1974;8:650–655. Not indexed in PubMed
Formula version: Cockcroft-Gault 1976 · MediHelp calc v1.0.1
Formula and sources checked on 2026-10-29
