Creatinine Clearance Calculator (Cockcroft-Gault)
Estimate creatinine clearance (CrCl) using the Cockcroft-Gault formula for kidney function assessment and drug dosing in adults.
How to use this tool
- Enter age, weight, serum creatinine and sex in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your creatinine clearance and the full breakdown beneath it.
Educational estimate — not medical advice. Consult a clinician.
The Cockcroft-Gault formula estimates creatinine clearance (CrCl) as a surrogate for GFR, widely used for drug dosing: CrCl = (140 − age) × weight ÷ (72 × Scr) [× 0.85 for women]. Many renally-dosed medications (aminoglycosides, enoxaparin, direct oral anticoagulants) specify dose adjustments by CrCl thresholds.
Formula
CrCl (mL/min) = [(140 − Age) × Weight (kg)] ÷ [72 × Scr (mg/dL)]
Multiply by 0.85 for females.
How it works
The Cockcroft-Gault (CG) formula, published in 1976, estimates creatinine clearance as a surrogate for GFR by relating age, body weight, sex, and serum creatinine. It remains the standard for pharmaceutical drug dosing adjustments in patients with renal impairment, as most drug labelling studies used CG rather than eGFR equations. This calculator applies the formula directly to inputs in the units shown; clinicians sometimes substitute adjusted or ideal body weight for obese patients to avoid overestimating renal function, a refinement not applied here, so results should be interpreted alongside clinical context and not used alone for drug-dosing decisions.
Worked example
Worked example
- Inputs: age = 50 years, weight = 70 kg, serum creatinine = 1.0 mg/dL, sex = male.
- Numerator = (140 − 50) × 70 = 90 × 70 = 6300.
- Denominator = 72 × 1.0 = 72.
- CrCl = 6300 ÷ 72 = 87.5 mL/min (no female correction needed).
Creatinine Clearance = 87.5 mL/min — Mildly reduced (60–89).
Key terms
- Creatinine clearance (CrCl)
- The volume of blood cleared of creatinine by the kidneys per minute; a proxy for glomerular filtration rate used especially in drug dosing.
- Cockcroft-Gault formula
- An empirical equation (1976) estimating CrCl from age, weight, sex, and serum creatinine; the reference standard for pharmaceutical dosing recommendations.
- Serum creatinine
- A metabolic waste product filtered by the kidneys; elevated levels reflect reduced filtration capacity.
- Renal drug dosing
- The adjustment of drug doses or dosing intervals based on kidney function to avoid toxicity from drug accumulation in patients with reduced clearance.
- Adjusted body weight
- A calculated weight used in obese patients to prevent overestimation of CrCl; Cockcroft-Gault with total body weight overestimates CrCl in obesity.
Frequently asked questions
- Which weight should I use?
- Use actual body weight if it is at or below ideal body weight. For obese patients, adjusted body weight (ABW) is often preferred; consult a pharmacist or physician for dosing decisions.
- How does CrCl differ from eGFR?
- Both estimate kidney function, but the CKD-EPI eGFR is normalised to 1.73 m² BSA and is preferred for CKD staging. CrCl from Cockcroft-Gault is preferred for drug dosing because most clinical trials used it to define dosing thresholds.