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Creatinine Clearance Calculator (Cockcroft-Gault)

Calculate creatinine clearance using the Cockcroft-Gault equation. Used for medication dosing adjustments in patients with kidney disease.

Reviewed by Chase FloiedUpdated

This free online creatinine clearance calculator (cockcroft-gault) provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Enter your values below and see results update in real time as you type. Perfect for everyday calculations, homework, or professional use.

How to Use This Calculator

1

Enter your input values

Fill in all required input fields for the Creatinine Clearance Calculator (Cockcroft-Gault). Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.

2

Review your inputs

Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.

3

Read the results

The Creatinine Clearance Calculator (Cockcroft-Gault) instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.

4

Explore parameter sensitivity

Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.

Formula Reference

Creatinine Clearance Calculator (Cockcroft-Gault) Formula

See calculator inputs for the governing equation

Variables: All variables and their units are labeled in the calculator interface above. Input fields accept values in multiple unit systems — select your preferred unit from the dropdown next to each field.

When to Use This Calculator

  • •Use the Creatinine Clearance Calculator (Cockcroft-Gault) for personal health tracking and wellness monitoring, establishing a baseline and tracking changes over time.
  • •Use it when recording fitness metrics to track progress toward health or athletic goals.
  • •Use it to compare measurements before and after a lifestyle, diet, or training change to quantify the impact.
  • •Use it as a conversation starter before a doctor's appointment, bringing objective data to discuss with a healthcare professional.

About This Calculator

The Creatinine Clearance Calculator (Cockcroft-Gault) is a free health and wellness calculation tool designed for personal use and general informational purposes. Calculate creatinine clearance using the Cockcroft-Gault equation. Used for medication dosing adjustments in patients with kidney disease. This calculator provides reference values based on established health screening formulas and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Results may vary based on individual factors not captured by the calculation. Consult a qualified healthcare provider for personalized health guidance. All calculations are performed locally in your browser — no personal health data is transmitted or stored.

About Creatinine Clearance Calculator (Cockcroft-Gault)

The Creatinine Clearance Calculator uses the Cockcroft-Gault equation, the standard tool for estimating kidney function in drug dosing. Developed in 1976, this formula remains the FDA-preferred method for determining medication dose adjustments despite newer GFR equations. It estimates how much creatinine your kidneys can clear from blood per minute, providing a practical index of renal function. Pharmacists and physicians rely on this calculator daily to dose medications like antibiotics, anticoagulants, and chemotherapy drugs safely in patients with kidney impairment. A 20% dosing error can be lethal for drugs with narrow therapeutic windows, making accurate creatinine clearance essential for safe medical care.

The Math Behind It

Creatinine clearance (CrCl) is the volume of blood plasma that is cleared of creatinine per unit time by the kidneys. It serves as a practical estimate of glomerular filtration rate (GFR) and is the gold standard for adjusting drug doses in patients with kidney disease. **The Cockcroft-Gault Equation**: CrCl = [(140 - age) × weight(kg)] / (72 × SCr) × (0.85 if female) Where: - Age in years - Weight in kilograms (use ideal body weight for obese patients) - SCr = Serum creatinine in mg/dL - Result in mL/min **Why Cockcroft-Gault?** Despite newer equations (MDRD, CKD-EPI), Cockcroft-Gault remains the FDA-preferred method because: 1. It's the equation used in FDA drug approval studies 2. Package inserts reference CrCl, not eGFR 3. It produces absolute mL/min (not normalized to BSA) 4. It's simple and doesn't require body surface area **Normal Values**: - Young adults: 90-140 mL/min - Age 65: 60-100 mL/min - Age 80+: 40-80 mL/min CrCl naturally declines ~1 mL/min per year after age 40. **Kidney Function Staging**: | CrCl (mL/min) | Kidney Function | |---------------|------------------| | >90 | Normal | | 60-89 | Mild decrease | | 30-59 | Moderate decrease (CKD Stage 3) | | 15-29 | Severe decrease (CKD Stage 4) | | <15 | Kidney failure (CKD Stage 5) | **Common Drug Dose Adjustments**: **Antibiotics**: - Vancomycin: Adjust based on CrCl - Aminoglycosides (gentamicin): Extend interval if CrCl <60 - Cefepime: Dose reduction for CrCl <60 **Anticoagulants**: - Enoxaparin: Reduce dose or avoid at CrCl <30 - Apixaban: Caution with CrCl <25 - Dabigatran: Avoid with CrCl <30 **Diabetes**: - Metformin: Contraindicated at CrCl <30 - SGLT2 inhibitors: Dose adjustments below CrCl 45-60 **Limitations**: 1. **Body weight**: Use ideal body weight for obese patients, actual weight if underweight. Formula is inaccurate at extremes. 2. **Muscle mass**: Overestimates in muscular patients, underestimates in cachectic patients 3. **Unstable creatinine**: Invalid during acute kidney injury when creatinine is rapidly changing 4. **Elderly**: May overestimate function in frail elderly with low muscle mass **When Accuracy Matters Most**: - Narrow therapeutic index drugs (digoxin, lithium, chemotherapy) - Drugs primarily cleared by kidneys (vancomycin, gentamicin) - Patients at extremes of age or body composition **24-Hour Urine Collection**: The most accurate measurement of creatinine clearance is a timed 24-hour urine collection, but this is cumbersome. Cockcroft-Gault is accurate enough for most clinical decisions.

Formula Reference

Cockcroft-Gault

CrCl = [(140 - age) × weight] / (72 × SCr) × (0.85 if female)

Variables: Age in years, weight in kg, SCr in mg/dL

Worked Examples

Example 1: Elderly Patient

75-year-old woman, 60 kg, serum creatinine 1.1 mg/dL. Needs gentamicin dosing.

Step 1:CrCl = [(140 - 75) × 60] / (72 × 1.1) × 0.85
Step 2:CrCl = [65 × 60] / 79.2 × 0.85
Step 3:CrCl = 3900 / 79.2 × 0.85
Step 4:CrCl = 49.2 × 0.85
Step 5:CrCl = 41.9 mL/min

CrCl ≈ 42 mL/min (moderate decrease). Gentamicin dosing interval should be extended (e.g., every 24-36 hours instead of every 8 hours) to prevent toxicity.

Example 2: Young Male

30-year-old man, 80 kg, creatinine 1.0 mg/dL.

Step 1:CrCl = [(140 - 30) × 80] / (72 × 1.0) × 1
Step 2:CrCl = (110 × 80) / 72
Step 3:CrCl = 8800 / 72
Step 4:CrCl = 122 mL/min

CrCl = 122 mL/min — normal, healthy kidney function. Standard medication dosing is appropriate.

Common Mistakes & Tips

  • !Using actual body weight in obese patients. Use ideal or adjusted body weight to avoid overestimating CrCl.
  • !Calculating CrCl during acute kidney injury when creatinine is rapidly rising — the equation isn't valid in this situation.
  • !Forgetting the 0.85 correction factor for women, which produces a 15% overestimate in female patients.
  • !Using CrCl for patients with unusual muscle mass (bodybuilders, amputees). Consider alternative methods.

Related Concepts

GFR Calculator

CKD-EPI — newer equation for CKD diagnosis.

BSA Calculator

Body surface area used for normalized GFR.

BMI Calculator

Helps decide when to use IBW for Cockcroft-Gault.

Used in These Calculators

Calculators that build on or apply the concepts from this page:

GFR Calculator (Kidney Function)

Ideal Body Weight Calculator (Devine)

Frequently Asked Questions

Which weight should I use for obese patients?

For obese patients (BMI >30 or >20% above ideal body weight), use ideal body weight (IBW) or adjusted body weight (AdjBW = IBW + 0.4 × (ABW - IBW)). Using actual body weight overestimates CrCl because fat tissue contributes little to creatinine production. Ideal body weight formulas: Men: 50 kg + 2.3 kg/inch over 5 ft; Women: 45.5 kg + 2.3 kg/inch over 5 ft.

Why does the FDA still use Cockcroft-Gault?

Most FDA drug approval studies and package inserts from the 1980s-2000s used Cockcroft-Gault for dose recommendations. Switching to newer equations (MDRD or CKD-EPI) would require restudying dozens of drugs. For consistency with labeling, FDA recommends using Cockcroft-Gault for dose adjustments even though newer equations are more accurate for diagnosing CKD.

What's the difference between CrCl and GFR?

GFR is the actual rate of plasma filtration through the glomerulus. CrCl approximates GFR but slightly overestimates it because creatinine is also secreted by renal tubules. GFR is indexed to body surface area (mL/min/1.73m²), while CrCl is typically unindexed (mL/min). For drug dosing, CrCl is preferred; for CKD staging, indexed GFR is preferred.

Should I use CrCl to monitor kidney disease progression?

No, use GFR (specifically eGFR from CKD-EPI). CrCl is designed for drug dosing, not disease staging. The newer equations (MDRD, CKD-EPI) are more accurate for diagnosing and monitoring CKD. Use Cockcroft-Gault specifically when adjusting medication doses or consulting drug labels that reference CrCl.