What is the Cockcroft and Gault calculator?
The Cockcroft-Gault calculator estimates creatinine clearance (CrCl) in mL/min. In clinical practice, this estimate is frequently used to help adjust doses for medicines that are eliminated by the kidneys. While newer equations are often used for chronic kidney disease staging, Cockcroft-Gault remains a widely referenced method in drug labeling and pharmacotherapy.
Cockcroft-Gault formula
The classic equation is:
CrCl = ((140 − age) × weight in kg) / (72 × serum creatinine in mg/dL)
For females, multiply the result by 0.85.
Variables used
- Age: in years
- Weight: usually actual body weight unless a different strategy is clinically indicated
- Serum creatinine: in mg/dL (or converted from µmol/L)
- Sex adjustment: 0.85 factor for females
How to use this calculator
- Enter age in years.
- Select sex.
- Enter weight and choose kg or lb.
- Enter serum creatinine and choose mg/dL or µmol/L.
- Click Calculate CrCl to view estimated creatinine clearance.
Interpreting the result
Creatinine clearance estimates are often interpreted in broad bands. These bands can support clinical thinking but are not a diagnosis by themselves:
- 90 mL/min or higher: generally preserved filtration for many adults
- 60–89 mL/min: mild reduction range
- 30–59 mL/min: moderate reduction range
- 15–29 mL/min: severe reduction range
- Below 15 mL/min: kidney failure range (requires urgent clinical context)
Medication dosing depends on more than one number. Always combine CrCl with clinical status, trend over time, and prescribing guidance.
Important clinical notes
1) Stable renal function matters
The Cockcroft-Gault equation assumes serum creatinine is at steady state. In acute kidney injury or rapidly changing renal function, this estimate may be misleading.
2) Weight choice can change dosing decisions
Different institutions use actual body weight, ideal body weight, or adjusted body weight depending on patient characteristics and medication. If your protocol specifies a weight method, follow that standard.
3) Not a replacement for clinical judgment
This calculator is educational and informational. For patient care decisions, use local guidelines, pharmacist input, and physician judgment.
Example calculation
Suppose a 68-year-old female weighs 62 kg and has serum creatinine 1.2 mg/dL:
- Base: ((140 − 68) × 62) / (72 × 1.2) = 51.7
- Female adjustment: 51.7 × 0.85 = 43.9 mL/min
Estimated CrCl is approximately 44 mL/min, often in a range where several renally cleared medications may require dose review.
Frequently asked questions
Is Cockcroft-Gault the same as eGFR?
No. They are related but not interchangeable. eGFR equations (such as CKD-EPI) are commonly used for kidney disease assessment, while Cockcroft-Gault is still frequently used for drug dosing.
Can I use this calculator for children?
No. Cockcroft-Gault is an adult equation. Pediatric kidney function is typically estimated with pediatric-specific formulas.
What if my creatinine is reported in µmol/L?
This tool converts µmol/L to mg/dL automatically using: mg/dL = µmol/L ÷ 88.4.
Bottom line
If you need a fast estimate of creatinine clearance for renal dosing workflows, the Cockcroft and Gault calculator remains practical and familiar. Use it carefully, interpret it in context, and confirm decisions with professional guidance when needed.