Calculate creatinine clearance using the Cockcroft-Gault equation with actual, ideal, and adjusted body weight. Review the result in renal-function and medication-dosing context.
The Creatinine Clearance (CrCl) Calculator uses the Cockcroft-Gault equation to estimate creatinine clearance from age, sex, serum creatinine, and body weight. Even though newer equations are often preferred for CKD staging, Cockcroft-Gault remains important because many medication references still describe renal dose adjustments in terms of CrCl rather than eGFR.
This page calculates CrCl with actual body weight, ideal body weight, and adjusted body weight so the effect of weight choice is visible. That is especially useful when the patient is obese, because using actual weight can overestimate clearance while using ideal body weight can underestimate it.
The result should be read as renal-dosing context rather than as a complete kidney assessment. Acute kidney injury, unstable creatinine, unusual muscle mass, pregnancy, amputations, and dialysis can all limit how well the estimate reflects the patient’s real filtration function.
Cockcroft-Gault is still the renal-function estimate behind many drug labels and dosing references, so the equation and weight choice matter. This page keeps the actual-, ideal-, and adjusted-weight calculations side by side so the renal-dosing context can be reviewed before checking the current drug-specific reference.
Cockcroft-Gault Equation: CrCl (mL/min) = [(140 − age) × weight (kg)] / [72 × serum creatinine (mg/dL)] × 0.85 if female Ideal Body Weight (Devine): Male: 50 + 2.3 × (height in inches − 60) Female: 45.5 + 2.3 × (height in inches − 60) Adjusted Body Weight: ABW = IBW + 0.4 × (actual weight − IBW) Used when actual weight > 120% of IBW
Result: CrCl = 63.2 mL/min (actual weight) — CKD Stage G2
CrCl = (140−65) × 85 / (72 × 1.4) = 63.2 mL/min. IBW = 50 + 2.3 × (68.9−60) = 70.5 kg. Because 85 kg is slightly above 120% of IBW (84.6 kg), the adjusted body weight is 76.3 kg and gives a CrCl of about 56.8 mL/min. The actual-, ideal-, and adjusted-weight results are close enough that this is still broadly a mild-reduction range, but the final dosing decision should come from the current drug-specific reference.
Developed in 1976 by Donald Cockcroft and Henry Gault, this equation was derived from a relatively small inpatient cohort. Despite its age and limitations, it remains widely used because many pharmacokinetic studies, legacy dose-adjustment tables, and package-insert recommendations still refer to Cockcroft-Gault creatinine clearance.
The equation assumes stable renal function and a creatinine value that reasonably reflects muscle mass. It can be less reliable in acute kidney injury, extremes of body composition, amputations, pregnancy, frailty, and other settings where creatinine production or steady-state assumptions break down. That is why the result should be used as one input into renal dosing, not as a stand-alone instruction.
When a drug reference asks for creatinine clearance, the key next step is to check the current manufacturer label, formulary, or institutional renal-dosing guideline for that specific medication. The calculator helps provide the Cockcroft-Gault estimate and shows how weight choice changes the number, but it does not replace drug-specific dosing references, therapeutic drug monitoring, or clinician judgment.
Last updated:
This page applies the Cockcroft-Gault equation using the entered age, sex, serum creatinine, and body weight, then shows the result with actual body weight, ideal body weight, and adjusted body weight when obesity could materially change the estimate. The goal is to make the weight-choice effect visible before the number is used in a renal-dosing lookup.
The result is intended as renal-dosing context rather than as a full kidney-function diagnosis. Cockcroft-Gault can be less reliable in acute kidney injury, unstable creatinine, unusual muscle mass, amputations, pregnancy, and dialysis, and drug-specific dosing should still come from the current label, formulary, or institutional reference rather than from this page alone.
GFR measures the kidney filtration rate normalized to body surface area, while Cockcroft-Gault CrCl is an older creatinine-clearance estimate that often runs somewhat higher because creatinine is both filtered and secreted. CKD staging is usually based on eGFR, but many drug references still point to Cockcroft-Gault CrCl.
For non-obese patients, use actual body weight. For obese patients (>120% of IBW), use adjusted body weight (ABW = IBW + 0.4 × [ABW − IBW]). Using actual weight in obese patients overestimates CrCl because excess fat does not produce creatinine proportionally.
CKD-EPI is generally preferred for estimating GFR and staging CKD, but many medication references still use Cockcroft-Gault because older pharmacokinetic work and labels were built around it. Which one matters most depends on whether you are staging kidney disease or looking up a renal dose adjustment.
No. Cockcroft-Gault was developed and validated in adults only. For pediatric patients, use the Schwartz equation (CrCl = k × height / SCr) or bedside Schwartz equation.
Women have less muscle mass per kilogram of body weight than men, resulting in lower creatinine production. The 0.85 correction factor accounts for this ~15% lower creatinine generation. Without this correction, CrCl would be overestimated in women.
Very low creatinine may indicate low muscle mass (elderly, cachectic, or amputee patients) and can produce falsely elevated CrCl estimates. Some practitioners round up to 1.0 mg/dL, but this practice lacks strong evidence and may lead to underdosing. Clinical judgment is essential.