Before the modern eGFR equations existed, doctors estimated kidney function with the Cockcroft-Gault formula — published in 1976 and still printed on drug labels today. Creatinine clearance estimates how many millilitres of blood the kidneys clear of creatinine per minute, and pharmaceutical companies use it to decide whether a drug dose needs adjusting for kidney impairment. It’s still the reference many dosing guidelines quote, especially for antibiotics, diabetes drugs, and blood thinners. Our free calculator applies the Cockcroft-Gault equation to your numbers instantly.
Creatinine Clearance Calculator
Estimate creatinine clearance with the Cockcroft-Gault equation.
The Cockcroft-Gault Equation
CrCl (mL/min) = ((140 − age) × weight (kg) × (0.85 if female)) ÷ (72 × serum creatinine in mg/dL)
The components are intuitive: (140 − age) captures declining kidney function with age, weight approximates muscle mass producing the creatinine, the 0.85 factor adjusts for typically lower muscle mass in women, and serum creatinine is what’s being cleared.
| CrCl | Interpretation |
|---|---|
| 90+ | Normal clearance |
| 60–89 | Mild decrease |
| 30–59 | Moderate decrease (many drugs need dose review) |
| 15–29 | Severe decrease |
| Below 15 | Kidney failure range |
How to Use the Creatinine Clearance Calculator
- Enter age, select sex, enter weight in kg, and serum creatinine in mg/dL (from your kidney function test).
- Click Calculate — your estimated creatinine clearance appears.
- Share it with your doctor or pharmacist before dose adjustments — never self-adjust medication.
Worked Example
A 65-year-old woman weighing 60 kg with creatinine 1.2 mg/dL: ((140 − 65) × 60 × 0.85) ÷ (72 × 1.2) = (75 × 51) ÷ 86.4 = 3825 ÷ 86.4 ≈ 44 mL/min — moderate decrease, where many drugs (e.g. certain antibiotics, metformin per local guidance) need a pharmacist’s review.
Important Notes
- This is an estimate, not medical advice. Drug dosing decisions belong to your doctor/pharmacist.
- Cockcroft-Gault overestimates clearance in obesity (it uses total weight) — clinicians sometimes use adjusted body weight; your doctor decides.
- Dehydration, muscle injury, and cooked-meat meals can temporarily shift creatinine.
Medical disclaimer: this is an estimate for information only – not medical advice. Consult your doctor before making any health decisions.
Frequently Asked Questions
Creatinine clearance vs eGFR — what’s the difference?
Both estimate kidney filtering. eGFR (CKD-EPI 2021) is indexed to body surface and is the standard for CKD staging; Cockcroft-Gault gives an absolute mL/min and remains the classic for drug-dose adjustment. Our eGFR calculator covers the other.
What is a normal creatinine clearance?
Roughly 90–140 mL/min in healthy adults, declining with age. Women run about 15% lower via the 0.85 factor.
Why 0.85 for women?
It approximates the average difference in muscle mass — less muscle means less creatinine produced, so the same blood level implies less clearance.
Does weight affect the result a lot?
Yes — that’s the formula’s weakness in obesity. Very high weights inflate the estimate, which is why doctors use clinical judgement (often adjusted body weight) in those cases.
Should I check creatinine clearance or eGFR?
For general kidney health: eGFR. For medication dosing questions: creatinine clearance is often what guidelines reference. When unsure, ask your pharmacist which one they want.
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