Creatinine Clearance Calculator (Cockcroft-Gault)

Formula

CrCl (mL/min) = ((140 − Age) × Weight × F) ÷ Serum creatinine

F = 1.23 (males) or 1.04 (females) when creatinine is in µmol/L. Use ideal or adjusted body weight in obesity.

Step-by-step method

1. 1

   Collect the inputs

   Note the patient’s age (years), weight (kg), sex, and most recent serum creatinine (µmol/L or mg/dL).

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.

3. 3

   Pick the sex factor

   Multiply by 1.23 for males or 1.04 for females when creatinine is in µmol/L (1.04 → 0.85 conversion when in mg/dL).

4. 4

   Apply the Cockcroft-Gault equation

   CrCl = ((140 − Age) × Weight × F) ÷ Serum creatinine.

5. 5

   Use CrCl to band the dose

   Compare against BNF renal-dose bands (typically <30, 30–50, 50–80 mL/min) and adjust the prescription accordingly.

Worked example

Scenario: 70-year-old male, 75 kg, serum creatinine 110 µmol/L.

Answer: ((140 − 70) × 75 × 1.23) ÷ 110 ≈ 58.7 mL/min.