Creatinine Clearance Calculator

What Is Creatinine Clearance?

Creatinine clearance (CrCl) is a measure of renal (kidney) function. It estimates how well the kidneys filter creatinine from the blood. Kidneys play vital roles including:

• Excreting metabolism waste products
• Formation of urine
• Regulation of serum osmolality
• Maintaining water and salt balance
• Acid-base balance
• Blood pressure regulation
• Hormone secretion

CrCl is measured when renal disease is suspected or when careful dosing of renally metabolized drugs is required.

The Cockcroft-Gault Equation

The Cockcroft-Gault equation, named after Dr. Donald William Cockcroft and Dr. Matthew Henry Gault (published in 1976), uses serum creatinine, weight, age, and sex to estimate creatinine clearance:

Where:

• age — patient's age in years
• weight — body weight in kg (adjusted based on BMI)
• sex_factor — 1.0 for males, 0.85 for females
• sCr — serum creatinine in mg/dL

Body Weight Adjustment

The Cockcroft-Gault equation uses body weight, but obesity can lead to overestimation because serum creatinine production is associated with lean body mass, not fat. The following adjustments are recommended:

BMI Category	Weight Used	Formula
Underweight (BMI <18.5)	Actual body weight	—
Normal (BMI 18.5–25)	Ideal body weight	IBW = 50 + 0.9 × (height_cm − 152) for males IBW = 45.5 + 0.9 × (height_cm − 152) for females
Overweight/Obese (BMI ≥25)	Adjusted body weight	ABW = IBW + 0.4 × (TBW − IBW)

Interpretation

CrCl (mL/min)	Stage	Interpretation
≥90	Normal	Normal kidney function
60–89	Mild decrease	Mildly reduced kidney function
30–59	Moderate decrease	Moderately reduced; clinical intervention may be needed
15–29	Severe decrease	Severely reduced; preparation for renal replacement therapy
<15	Kidney failure	Renal replacement therapy (dialysis or transplant) indicated

Note: After age 40, GFR decreases progressively by 0.4–1.2 mL/min per year, so values above 60 mL/min may be considered normal in older patients with no other kidney disease markers.

Worked Example

Patient: 67-year-old male, weight 92 kg, height 173 cm, serum creatinine 1.4 mg/dL.

This result of 56.6 mL/min indicates moderately decreased kidney function.

Other Creatinine Clearance Formulas

Apart from the Cockcroft-Gault equation, GFR can also be estimated using:

• CKD-EPI Creatinine Equation — recommended by KDIGO guidelines
• CKD-EPI Creatinine-Cystatin Equation
• CKD-EPI Cystatin C Equation
• MDRD Study Equation

Direct CrCl Calculation

Creatinine clearance can also be calculated directly using both serum (sCr) and urine creatinine (uCr), along with urine volume. While reliable, this method is less popular due to the inconvenient 24-hour urine collection requirement:

Frequently Asked Questions

What is a normal creatinine clearance?

Normal creatinine clearance is ≥90 mL/min. However, values above 60 mL/min are often considered acceptable in older patients when no other kidney disease markers are present.

Why does the calculator adjust for body weight?

Serum creatinine is produced by muscle tissue, not fat. Using actual body weight in obese patients overestimates CrCl because their excess weight is fat, not muscle. The adjusted body weight (ABW) formula accounts for this.

What is serum creatinine?

Serum creatinine is a waste product produced by muscles from the breakdown of creatine. Healthy kidneys filter creatinine from the blood. When kidney function declines, serum creatinine levels rise.

When should I use this calculator?

This calculator is useful for estimating kidney function for drug dosing, monitoring renal disease progression, or screening for chronic kidney disease. It's commonly used in clinical pharmacy and internal medicine.