What this CrCl calculator does
This calculator estimates creatinine clearance (CrCl) using the Cockcroft-Gault equation, a commonly used method for medication dose adjustment. In many clinical workflows, CrCl remains the preferred value for renal dosing decisions, especially when prescription labeling is based on Cockcroft-Gault rather than eGFR.
You can enter age, sex, body weight, and serum creatinine using common units. The tool then calculates:
- Estimated CrCl in mL/min
- Renal function category for quick interpretation
- Weight actually used in the equation (ABW, IBW, or AdjBW)
- Optional normalized CrCl in mL/min/1.73 m² when height is provided
Formula used (Cockcroft-Gault)
The equation implemented is:
CrCl = ((140 - age) × weight in kg) / (72 × serum creatinine in mg/dL)
For females, the estimate is multiplied by 0.85.
Unit conversions
- Serum creatinine conversion:
mg/dL = µmol/L ÷ 88.4 - Weight conversion:
kg = lb ÷ 2.20462 - Height conversion:
cm = in × 2.54
How to interpret your CrCl result
| CrCl (mL/min) | Typical interpretation |
|---|---|
| ≥ 90 | Normal or near-normal kidney function |
| 60–89 | Mildly decreased function |
| 30–59 | Moderately decreased function |
| 15–29 | Severely decreased function |
| < 15 | Kidney failure range (clinical confirmation required) |
Choosing ABW, IBW, or AdjBW
Weight selection can materially change the CrCl estimate, and that can affect drug dosing. There is no one-size-fits-all answer; institutions often have protocol-specific rules.
Common approach
- ABW (Actual Body Weight): Often used by default.
- IBW (Ideal Body Weight): Sometimes preferred in underweight or select populations.
- AdjBW (Adjusted Body Weight): Frequently considered when obesity may overestimate renal function using ABW.
IBW is calculated using the Devine formula:
- Male:
IBW = 50 + 2.3 × (inches over 5 feet) - Female:
IBW = 45.5 + 2.3 × (inches over 5 feet)
Adjusted body weight is:
AdjBW = IBW + 0.4 × (ABW - IBW)
Important limitations
- This is an estimate, not a direct measurement of GFR.
- Results may be less reliable in rapidly changing kidney function (AKI), pregnancy, amputees, extremes of muscle mass, or unstable creatinine production.
- Use lab trends, urine output, clinical context, and drug-specific guidance before final dosing decisions.
- Always follow institutional protocols and licensed clinician judgment.
Quick usage tips
1) Use consistent, current lab data
Enter the most recent stable serum creatinine and current weight. Small data mismatches can cause clinically meaningful differences in estimated clearance.
2) Match the metric to the drug label
Some medications are dose-adjusted by Cockcroft-Gault CrCl, while others may reference eGFR. Check the official labeling and your local formulary guidance.
3) Recalculate when condition changes
If volume status, muscle mass, or creatinine shifts, repeat the estimate and reassess dosing. Renal function is dynamic, especially in acute care settings.
This page is for educational use and workflow support. It does not replace direct medical evaluation.