Creatinine Clearance Calculator
Calculate creatinine clearance (CrCl) using the Cockcroft-Gault equation for drug dosing and kidney function assessment.
Patient Information
years
Creatinine Clearance
77.0 mL/min
Mild
⚖️CrCl (Actual Weight)
77.0 mL/min
📊CrCl (IBW)
72.5 mL/min
🎯Ideal Body Weight
65.9 kg
📈Adjusted Body Weight
67.6 kg
Interpretation
Mildly reduced kidney function
Cockcroft-Gault Formula
Formula
CrCl = [(140 - age) x weight] / (72 x SCr)
Multiply by 0.85 if female
Clinical Use
- Drug dosing adjustments
- Antibiotic dose calculations
- Contrast agent protocols
- Chemotherapy dosing
What is Creatinine Clearance (CrCl)?
Creatinine clearance (CrCl) is a measurement that estimates how well your kidneys filter creatinine from the blood. It's one of the most important indicators of kidney function and is essential for determining appropriate medication dosages.
Why CrCl Matters:
- Drug Dosing: Many medications require dose adjustments based on kidney function
- Kidney Health: Indicates how well kidneys are filtering blood
- Disease Monitoring: Tracks progression of kidney disease
- Pre-Surgery Assessment: Important for surgical risk evaluation
Creatinine Clearance Ranges:
| CrCl (mL/min) | Kidney Function | Drug Dosing |
|---|---|---|
| >90 | Normal | Standard doses |
| 60-89 | Mildly reduced | Monitor; some adjustments |
| 30-59 | Moderately reduced | Dose adjustments often needed |
| 15-29 | Severely reduced | Significant adjustments; avoid some drugs |
| <15 | Kidney failure | Many drugs contraindicated |
The Cockcroft-Gault Formula
The Cockcroft-Gault equation is the most widely used formula for estimating creatinine clearance, particularly for drug dosing:
Cockcroft-Gault Equation
CrCl (mL/min) = [(140 - age) × weight (kg)] / [72 × serum creatinine (mg/dL)]
For females: Multiply result × 0.85
Using Ideal Body Weight (IBW) if obese:
Males: IBW = 50 + 2.3 × (height in inches - 60)
Females: IBW = 45.5 + 2.3 × (height in inches - 60)
Use IBW if actual weight > IBW
Use actual weight if actual < IBW
Where:
- CrCl= Creatinine clearance in mL/min
- Age= Patient age in years
- Weight= Body weight in kg (use IBW if obese)
- SCr= Serum creatinine in mg/dL
How to Use This Calculator
Our calculator estimates creatinine clearance using the Cockcroft-Gault formula:
- Enter Age: Patient's age in years
- Enter Weight: Body weight in kg or lbs
- Enter Height: Height in cm or feet/inches (for IBW calculation)
- Select Sex: Male or female (affects the calculation)
- Enter Serum Creatinine: Lab value in mg/dL or μmol/L
- View Results:
- Estimated CrCl (mL/min)
- Kidney function category
- Ideal body weight calculation
- Drug dosing implications
Important Notes:
- This is an estimate, not a measured value
- Results may be inaccurate in certain conditions (see limitations)
- Always confirm medication dosing with a healthcare provider or pharmacist
- For critical decisions, measured 24-hour urine CrCl is more accurate
CrCl vs. eGFR: What's the Difference?
Two related but different measures of kidney function:
Creatinine Clearance (CrCl) - Cockcroft-Gault:
- Developed in 1976, still used today
- Standard for drug dosing decisions
- FDA drug labels typically reference CrCl
- Uses actual body weight (or IBW if obese)
- Not standardized to body surface area
eGFR (CKD-EPI or MDRD):
- More recent equations (2009, 2021 updates)
- Used for chronic kidney disease (CKD) staging
- Standardized to body surface area (mL/min/1.73m²)
- More accurate for estimating actual kidney function
- Automatically calculated by most labs
When to Use Which:
| Purpose | Use This |
|---|---|
| Drug dosing | CrCl (Cockcroft-Gault) |
| CKD staging/diagnosis | eGFR (CKD-EPI) |
| Tracking kidney disease progression | eGFR (CKD-EPI) |
| Contrast dye decisions | eGFR (usually) |
Body Weight Considerations
Choosing the correct weight for the formula is crucial:
Use Actual Body Weight (ABW) When:
- Patient is at or below ideal body weight
- Patient is slightly overweight but not obese
- For hydrophilic drugs that don't distribute into fat
Use Ideal Body Weight (IBW) When:
- Patient is significantly obese (ABW >120% of IBW)
- Fat tissue doesn't produce much creatinine
- Most commonly recommended approach for obese patients
Use Adjusted Body Weight (AdjBW) When:
- Some practitioners use for very obese patients
- AdjBW = IBW + 0.4 × (ABW - IBW)
- Accounts for some contribution from excess weight
Ideal Body Weight Formulas:
- Males: IBW (kg) = 50 + 2.3 × (height inches - 60)
- Females: IBW (kg) = 45.5 + 2.3 × (height inches - 60)
- For height <60 inches, use actual body weight
Limitations and Special Populations
The Cockcroft-Gault formula has important limitations:
May Be Inaccurate In:
- Unstable kidney function: When creatinine is rapidly changing
- Extremes of body size: Very low or very high weight
- Low muscle mass: Elderly, malnourished, amputees, paraplegics
- High muscle mass: Bodybuilders, athletes
- Pregnancy: Physiological changes affect creatinine
- Liver disease: May have lower creatinine production
- Vegetarian diet: Lower creatinine from diet
- Creatine supplements: Falsely elevates creatinine
Medications That Affect Serum Creatinine:
- Trimethoprim: Blocks creatinine secretion, raises SCr without affecting true GFR
- Cimetidine: Similar effect
- Certain cephalosporins: May interfere with assay
When to Use 24-Hour Urine Collection:
- Extremes of body size or muscle mass
- Uncertainty about estimate accuracy
- Critical drug dosing decisions
- Dietary extremes (vegetarian, high protein)
Drug Dosing Based on CrCl
Many medications require dose adjustments based on kidney function:
Common Drug Categories Needing Adjustment:
- Antibiotics: Aminoglycosides, fluoroquinolones, vancomycin, many others
- Antivirals: Acyclovir, ganciclovir, oseltamivir
- Diabetes medications: Metformin, many others
- Blood thinners: DOACs (apixaban, rivaroxaban), enoxaparin
- Pain medications: NSAIDs (avoid), gabapentin, pregabalin
- Heart medications: Digoxin, sotalol, ACE inhibitors
General Dosing Adjustments:
| CrCl Range | Typical Adjustment |
|---|---|
| >50 mL/min | Usually normal dose |
| 30-50 mL/min | Often 50-75% of dose or extended interval |
| 10-30 mL/min | Often 25-50% of dose |
| <10 mL/min | May need to avoid or give minimally |
Always check specific drug recommendations - the above are generalizations.
Worked Examples
Calculate CrCl for a Male Patient
Problem:
65-year-old male, 70 kg, serum creatinine 1.2 mg/dL. Calculate CrCl.
Solution Steps:
- 1Age: 65 years, Weight: 70 kg, SCr: 1.2 mg/dL
- 2Apply Cockcroft-Gault formula:
- 3CrCl = [(140 - 65) × 70] / [72 × 1.2]
- 4CrCl = [75 × 70] / 86.4
- 5CrCl = 5250 / 86.4
- 6CrCl = 60.8 mL/min
- 7Category: Mildly reduced kidney function
Result:
CrCl: 61 mL/min | Mild reduction - may need dose adjustments for some medications
Calculate CrCl for a Female Patient
Problem:
72-year-old female, 65 kg, serum creatinine 1.0 mg/dL. Calculate CrCl.
Solution Steps:
- 1Age: 72 years, Weight: 65 kg, SCr: 1.0 mg/dL, Sex: Female
- 2CrCl = [(140 - 72) × 65] / [72 × 1.0]
- 3CrCl = [68 × 65] / 72
- 4CrCl = 4420 / 72 = 61.4 mL/min
- 5Apply female correction: 61.4 × 0.85 = 52.2 mL/min
- 6Category: Moderately reduced kidney function
Result:
CrCl: 52 mL/min | Moderate reduction - dose adjustments likely needed
Obese Patient Using IBW
Problem:
55-year-old male, actual weight 120 kg, height 5'10" (70 inches), SCr 0.9 mg/dL.
Solution Steps:
- 1Calculate IBW: 50 + 2.3 × (70 - 60) = 50 + 23 = 73 kg
- 2Actual weight (120 kg) > IBW (73 kg), so use IBW
- 3CrCl = [(140 - 55) × 73] / [72 × 0.9]
- 4CrCl = [85 × 73] / 64.8
- 5CrCl = 6205 / 64.8 = 95.8 mL/min
- 6Using actual weight would overestimate: ~157 mL/min
Result:
CrCl: 96 mL/min (using IBW) | Normal kidney function | Using IBW for obese patient
Tips & Best Practices
- ✓Use ideal body weight for obese patients to avoid overestimating CrCl
- ✓The Cockcroft-Gault equation is still the standard for most drug dosing decisions
- ✓Always verify drug-specific dosing recommendations - don't rely on general guidelines alone
- ✓For critical decisions, consider 24-hour urine collection for measured CrCl
- ✓Low muscle mass patients may have falsely high CrCl despite poor kidney function
- ✓Convert creatinine units correctly: μmol/L ÷ 88.4 = mg/dL
- ✓CrCl and eGFR are related but used for different purposes
- ✓Declining CrCl over time should prompt kidney function evaluation
Frequently Asked Questions
Most FDA drug labeling and dosing recommendations were developed using the Cockcroft-Gault equation, which was the standard when these drugs were studied. While eGFR (CKD-EPI) is generally more accurate for estimating true kidney function, using it for drug dosing could lead to mismatches with the original study populations. For consistency and safety, Cockcroft-Gault remains the standard for drug dosing unless specifically stated otherwise in drug labeling.
Low serum creatinine (often seen in elderly, malnourished, or low-muscle-mass patients) can paradoxically give falsely high CrCl estimates. Some practitioners round up very low creatinine values to 1.0 mg/dL for dosing purposes, though this is controversial. The issue is that patients with low muscle mass may actually have poor kidney function masked by low creatinine. Clinical judgment and sometimes measured 24-hour CrCl are needed in these cases.
For obese patients (actual weight >120% of IBW), ideal body weight is generally recommended because adipose tissue contributes minimally to creatinine production. For underweight patients, use actual weight. For normal-weight patients, either is appropriate. Some clinicians use adjusted body weight for very obese patients. The choice can significantly affect the calculated CrCl and resulting drug doses.
Serum creatinine is measured in mg/dL (US) or μmol/L (most other countries). To convert: μmol/L ÷ 88.4 = mg/dL, or mg/dL × 88.4 = μmol/L. Most CrCl calculators expect mg/dL, so conversion may be necessary. A typical normal creatinine of 1.0 mg/dL equals approximately 88 μmol/L.
Women typically have less muscle mass than men of the same weight, so they produce less creatinine. The 0.85 correction factor accounts for this difference. Without the correction, CrCl would be overestimated in women. This factor was derived from the original Cockcroft-Gault study population.
Yes. Young, muscular individuals, pregnant women, or those with high protein intake may have CrCl above 120-140 mL/min. In pregnancy, physiological changes increase kidney blood flow and filtration. Athletes may have high CrCl due to increased muscle mass and blood flow. A high calculated CrCl is not concerning unless there are other signs of kidney problems.
Sources & References
Last updated: 2026-01-22