{ "slug": "creatinine-clearance-cockcroft-gault", "title": "Creatinine Clearance Calculator (Cockcroft-Gault)", "heading": "Creatinine Clearance Calculator", "category": "fitness-health", "url": "https://www.revenuelab.fyi/toolbox/creatinine-clearance-cockcroft-gault", "summary": "Estimate CrCl for drug dosing using the Cockcroft-Gault equation.", "description": "Cockcroft-Gault estimates creatinine clearance from age, weight, sex, and serum creatinine, and it remains the standard equation referenced in most drug package inserts for renal dose adjustment, especially for agents like vancomycin, DOACs, and many antibiotics. Unlike eGFR equations built for CKD staging, Cockcroft-Gault was derived and validated specifically for dosing decisions, which is why pharmacists and prescribers still reach for it even though eGFR (CKD-EPI) is preferred for diagnosing kidney disease. The formula uses actual body weight by default, but many clinicians substitute ideal or adjusted body weight in obese patients to avoid overestimating clearance, since creatinine generation does not scale with fat mass the way it does with lean tissue. Results are unreliable in unstable renal function, extremes of muscle mass, amputees, or during acute kidney injury, where creatinine has not reached steady state. Always check the specific drug label for which weight input it expects. This tool is for education and workflow support only — not medical advice. Always verify results with a clinician and use clinical judgment alongside your institution's protocols.", "formula": "CrCl (mL/min) = [(140 − age) × weight(kg) × (0.85 if female)] ÷ (72 × Scr mg/dL).", "dateModified": "2026-09-30", "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=creatinine-clearance-cockcroft-gault", "inputs": [ { "id": "age", "label": "Age", "kind": "number", "hint": null, "default": 65, "unit": "years", "min": 18, "max": 110 }, { "id": "weight", "label": "Weight", "kind": "number", "hint": null, "default": 80, "unit": "kg", "min": 20, "max": 250 }, { "id": "scr", "label": "Serum creatinine", "kind": "number", "hint": null, "default": 1.1, "unit": "mg/dL", "min": 0.2, "max": 15 }, { "id": "sex", "label": "Sex", "kind": "select", "hint": null, "default": "male", "options": [ { "value": "male", "label": "Male" }, { "value": "female", "label": "Female" } ] } ], "outputs": [ { "id": "crcl", "label": "Creatinine clearance", "format": "decimal", "hint": null, "primary": true }, { "id": "band", "label": "Function category", "format": "raw", "hint": null, "primary": false } ], "worked_example": { "inputs": [ "Age: 65 years", "Weight: 80 kg", "Serum creatinine: 1.1 mg/dL", "Sex: Male" ], "outputs": [ "Creatinine clearance: 75.8", "Function category: Mildly reduced" ] }, "how_to": { "title": "How to use this", "steps": [ "Enter age (years).", "Enter weight (kg).", "Enter serum creatinine (mg/dL).", "Enter sex.", "Read your creatinine clearance on the right — it updates as you type.", "Hit Share to keep the scenario or send it to someone." ] }, "scenarios": [ { "name": "Conservative", "description": "Lower-end numbers — what if things land soft?", "values": { "age": 65, "weight": 80, "scr": 0.66, "sex": "male" } }, { "name": "Typical", "description": "Defaults — the most common real-world setup.", "values": { "age": 65, "weight": 80, "scr": 1.1, "sex": "male" } }, { "name": "Ambitious", "description": "Higher-end numbers — what if things really pop?", "values": { "age": 65, "weight": 80, "scr": 1.7600000000000002, "sex": "male" } } ], "limitations": [ "Population formulas describe averages; individual bodies vary, especially at the extremes of height, age, or muscle mass.", "Results do not account for medical conditions, medication, or pregnancy.", "Use this as a directional reference, not a diagnosis — talk to a clinician before acting on it." ], "faq": [ { "q": "Should I use actual or ideal body weight?", "a": "Use actual body weight if the patient is at or under ideal body weight. If actual weight exceeds ideal weight by more than about 20-30%, most pharmacists switch to adjusted body weight (ideal + 0.4 × excess weight) because fat contributes little to creatinine production and using actual weight would overestimate clearance and risk overdosing." }, { "q": "Why not just use eGFR for dosing?", "a": "eGFR equations like CKD-EPI are normalized to a standard 1.73 m² body surface area, which is useful for staging chronic kidney disease across a population but can misrepresent an individual patient's actual clearance, particularly at extremes of body size. Cockcroft-Gault reports an un-normalized value tied to the patient's real body, which is what drug clearance actually depends on." }, { "q": "How reliable is this in acute kidney injury?", "a": "Not very. The equation assumes creatinine is at steady state, which is not true during rapidly changing renal function. In AKI, serum creatinine lags the real-time GFR, so calculated clearance can look falsely reassuring on the way down and falsely low on the way up. Use direct measurement or clinical judgment instead." }, { "q": "Does muscle mass affect the result?", "a": "Yes, significantly. Serum creatinine comes from muscle breakdown, so a frail, low-muscle-mass elderly patient can have a 'normal' creatinine despite meaningfully reduced kidney function, while a bodybuilder can have an elevated creatinine with normal kidneys. Interpret extreme muscle mass cases cautiously." } ], "related": [ "https://www.revenuelab.fyi/toolbox/ideal-body-weight", "https://www.revenuelab.fyi/toolbox/adjusted-body-weight", "https://www.revenuelab.fyi/toolbox/fena-calculator" ], "license": "CC-BY-4.0", "citation": "RevenueLab — Creatinine Clearance Calculator (Cockcroft-Gault) (https://www.revenuelab.fyi/toolbox/creatinine-clearance-cockcroft-gault)" }