Calculate creatinine clearance using the Cockcroft-Gault equation with actual, ideal, and adjusted body weight. Includes CKD staging and drug dosing guidance.
The Creatinine Clearance (CrCl) Calculator uses the Cockcroft-Gault equation — the most widely used formula for estimating renal function in drug dosing. Originally published in 1976, the Cockcroft-Gault equation remains the standard referenced in most drug package inserts and FDA dosing guidelines, making it essential for pharmacists, physicians, and nurses adjusting medication doses for kidney function.
This calculator computes CrCl using three weight methods: actual body weight (ABW), ideal body weight (IBW), and adjusted body weight (AdjBW). The choice of weight matters significantly for obese patients, where using actual weight may overestimate kidney function and using IBW may underestimate it. The adjusted body weight (IBW + 0.4 × [ABW − IBW]) is recommended for patients exceeding 120% of their IBW.
Results include CKD staging based on the calculated CrCl, drug dosing guidance with thresholds for common renally-excreted medications, and a reference table of dose adjustments for frequently prescribed drugs. Whether you're calculating enoxaparin dosing, adjusting vancomycin intervals, or determining metformin safety, this calculator provides the clinical decision support you need.
Most drug dosing guidelines reference Cockcroft-Gault CrCl, not CKD-EPI eGFR. Using the wrong equation (or the wrong body weight) can lead to overdosing (toxicity) or underdosing (treatment failure) of critical medications. This calculator provides all three weight-based calculations side by side to support accurate clinical decision-making. Keep these notes focused on your operational context.
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. Since 85 kg < 120% of IBW (84.6 kg), ABW is close to actual. CrCl with IBW = 52.4 mL/min. CKD Stage G2 (mildly decreased). Most drugs can be dosed normally at CrCl > 50.
Developed in 1976 by Donald Cockcroft and Henry Gault, this equation was derived from 249 patients at Queen Mary Veterans Hospital in Montreal. Despite being nearly 50 years old and having known limitations, it remains the reference standard for drug dosing because virtually all pharmacokinetic studies and drug labels reference Cockcroft-Gault CrCl.
The equation assumes stable renal function (not applicable in acute kidney injury), normal muscle mass (may overestimate in cachectic patients), and standard diet. It has not been validated in extremes of age (<18 or >90), pregnancy, or amputees. It also uses creatinine assays that have evolved since 1976 — IDMS-standardized assays produce lower creatinine values, potentially overestimating CrCl by 10–40% in patients with near-normal renal function.
Renally-excreted drugs accumulate when CrCl decreases, increasing the risk of toxicity. Common drugs requiring dose adjustment: antibiotics (vancomycin, aminoglycosides, fluoroquinolones), anticoagulants (enoxaparin, DOACs), analgesics (gabapentin, pregabalin), antihypertensives (ACE inhibitors, ARBs), and diabetes medications (metformin, sulfonylureas). Always check current drug references for specific CrCl thresholds.
GFR (glomerular filtration rate) measures the rate at which kidneys filter blood, expressed in mL/min/1.73m². CrCl (creatinine clearance) measures how quickly creatinine is cleared and includes both glomerular filtration and tubular secretion, so CrCl typically overestimates GFR by 10–20%. Drug dosing guidelines usually reference CrCl (Cockcroft-Gault).
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 more accurate for estimating true GFR and is preferred for CKD staging. However, most drug labels and dosing guidelines were developed using Cockcroft-Gault CrCl. Use CKD-EPI for diagnosis and prognosis, Cockcroft-Gault for drug dosing.
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.