Creatinine Clearance Calculator (Cockcroft-Gault)

Formula

CrCl (mL/min) = ((140 − Age) × Weight (kg)) ÷ (72 × SCr [mg/dL]) × 0.85 if female

Use the mg/dL form in US practice (multiply final by 0.85 for females). Use ideal or adjusted body weight in obesity per institutional policy.

Step-by-step method

1. 1

   Collect the inputs

   Note the patient's age (years), weight (kg), sex, and most recent serum creatinine (mg/dL preferred in US practice; µmol/L also accepted).

2. 2

   Choose the right body weight

   Use actual body weight in normal-range patients. In obesity (BMI > 30) use ideal or adjusted body weight per local policy. Use ideal body weight for aminoglycoside dosing.

3. 3

   Apply the Cockcroft-Gault equation (mg/dL form)

   CrCl = ((140 − Age) × Weight) ÷ (72 × SCr in mg/dL).

4. 4

   Apply the female correction

   Multiply the result by 0.85 if the patient is female.

5. 5

   Use CrCl to band the dose

   Compare against FDA-labeled renal-dose bands (commonly <30, 30–50, 50+ mL/min) and adjust the prescription per the package insert and Lexicomp / Micromedex.

Worked example

Scenario: 70-year-old male, 75 kg, serum creatinine 1.2 mg/dL.

Answer: ((140 − 70) × 75) ÷ (72 × 1.2) = 60.8 mL/min.