Creatinine Clearance Calculator (Cockcroft-Gault) in mg/dL and µmol/L
Estimate creatinine clearance (CrCl) with the Cockcroft-Gault equation. Choose actual, ideal or adjusted body weight and enter creatinine in mg/dL or µmol/L.
✓ Formulas cited from the published literature
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About this calculator
Creatinine clearance estimates how much blood the kidneys filter per minute, based on the serum creatinine level. Despite newer eGFR equations, the Cockcroft-Gault equation is still the one most drug labels and renal-dosing references use, which is why pharmacists rely on it daily.
Because the choice of body weight changes the answer substantially in obese or underweight patients, this calculator shows the result with actual, ideal and adjusted weight side by side.
How it works
CrCl (mL/min) = [(140 − age) × weight (kg)] ÷ [72 × serum creatinine (mg/dL)] × 0.85 if female
Ideal body weight (Devine): men 50 kg + 2.3 kg per inch over 5 feet; women 45.5 kg + 2.3 kg per inch over 5 feet.
Adjusted body weight: IBW + 0.4 × (actual weight − IBW).
Unit conversion: creatinine in µmol/L ÷ 88.4 = mg/dL.
How to read your result
| CrCl (mL/min) | Interpretation |
|---|---|
| ≥ 90 | Normal or high |
| 60–89 | Mildly decreased |
| 30–59 | Moderately decreased |
| 15–29 | Severely decreased |
| < 15 | Kidney failure range |
Which weight? Common practice is actual weight when it is below ideal; ideal weight for normal weight; and adjusted weight when actual weight exceeds roughly 120–130% of ideal. Institutional protocols vary, so follow your local policy. Dose adjustment thresholds differ by drug and are given in each product's labelling.
Worked example
A 70-year-old man, 82 kg, 172 cm, serum creatinine 1.4 mg/dL, using actual body weight.
| Creatinine clearance | 57 mL/min Moderately decreased (30–59 mL/min) |
| Using actual weight (82 kg) | 57 mL/min |
| Using ideal weight (67.7 kg) | 47 mL/min |
| Using adjusted weight (73.4 kg) | 51 mL/min |
Frequently asked questions
What is the Cockcroft-Gault equation?
It is a formula published in 1976 that estimates creatinine clearance from age, weight, sex and serum creatinine. Most pharmacokinetic studies behind drug dosing recommendations used it.
Cockcroft-Gault or eGFR for drug dosing?
Many drug labels still specify Cockcroft-Gault CrCl. Regulatory guidance allows eGFR in many cases, but for narrow-therapeutic-index or renally cleared drugs follow the label and local policy.
Which weight should I use in obese patients?
Practice varies. Adjusted body weight is widely used when actual weight exceeds about 120–130% of ideal weight, but no single method is validated for all patients.
How do I convert creatinine from µmol/L to mg/dL?
Divide by 88.4. For example 124 µmol/L is about 1.4 mg/dL. This calculator converts automatically when you choose µmol/L.
When is the equation unreliable?
In acute kidney injury (creatinine not at steady state), extremes of muscle mass, amputees, liver disease, pregnancy and children.
Limitations and when not to use
Only valid for adults with stable renal function. Creatinine overestimates function in sarcopenia and frail older adults. Never use this result alone to prescribe or adjust a drug dose.
Sources and references
- Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron 1976;16:31–41.
- Devine BJ. Gentamicin therapy. Drug Intell Clin Pharm 1974;8:650–655.
- FDA Guidance for Industry. Pharmacokinetics in Patients with Impaired Renal Function: Study Design, Data Analysis, and Impact on Dosing, 2020.
Last updated: 2026-10-09