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Creatinine Clearance Calculator

Estimate renal function using the Cockcroft-Gault equation. Includes MDRD eGFR, CKD staging, IBW/ABW weight correction, and renal dose adjustment guidance.

Cockcroft-Gault Formula (Primary — Drug Dosing)
CrCl = [(140 − Age) × Weightkg × F] / (72 × SCrmg/dL)
F = 1.0 (male)    F = 0.85 (female)    SCr = Serum Creatinine
MDRD eGFR = 175 × SCr−1.154 × Age−0.203 × (0.742 if female) × (1.212 if Black)
CrCl — Cockcroft-Gault
—
mL/min Primary (Dosing)
eGFR — MDRD
—
mL/min/1.73m² Reference (eGFR)
Weight Used
—
Dose Adjustment Note: Renal dosing adjustment may be required for medications with renal clearance at this CrCl level. Always verify with current prescribing information.

How to Use

1
Enter the patient's age in years (18–120).
2
Select sex — this affects both the Cockcroft-Gault factor (0.85 for female) and the MDRD multiplier.
3
Enter body weight in kg or lbs. The calculator converts automatically.
4
Enter serum creatinine — select the correct unit (mg/dL or μmol/L). μmol/L values are converted by dividing by 88.4.
5
Optionally enter height to enable Ideal Body Weight (IBW) and Adjusted Body Weight (ABW) calculations for obese patients. The calculator will automatically determine which weight to use in the formula.

Worked Example

Example Calculation

Patient: 65-year-old female, weight 70 kg, serum creatinine 1.2 mg/dL

CrCl = [(140 − 65) × 70 × 0.85] / (72 × 1.2)

= [75 × 70 × 0.85] / 86.4 = 4462.5 / 86.4 = 51.7 mL/min

CKD Classification: Stage 3a — Mildly to Moderately Decreased (45–59 mL/min)

About the Cockcroft-Gault Equation

The Cockcroft-Gault equation, developed in 1976, remains the standard formula for estimating creatinine clearance for drug dosing purposes. It uses age, sex, body weight, and serum creatinine as variables, reflecting the physiological relationship between muscle mass, creatinine production, and renal excretion.

The MDRD (Modification of Diet in Renal Disease) equation provides an estimated GFR normalized to body surface area (mL/min/1.73 m²), making it more useful for CKD staging and monitoring kidney disease progression. Unlike Cockcroft-Gault, MDRD does not require body weight and includes a race correction factor based on the original study population.

For obese patients, Adjusted Body Weight (ABW) is recommended for Cockcroft-Gault because adipose tissue contributes little to creatinine production. ABW = IBW + 0.4 × (Actual − IBW), where IBW is calculated using the Devine formula.

CKD Stage Classification

The following thresholds are used by this calculator for CKD staging based on eGFR/CrCl:

Stage 1: ≥ 90 — Normal Stage 2: 60–89 — Mildly Decreased Stage 3a: 45–59 — Mildly to Moderately Decreased Stage 3b: 30–44 — Moderately to Severely Decreased Stage 4: 15–29 — Severely Decreased Stage 5: < 15 — Kidney Failure

Frequently Asked Questions

Creatinine clearance (CrCl) is used to estimate kidney function, specifically to calculate drug doses for medications that are cleared by the kidneys. Many drugs — including antibiotics, anticoagulants, and cardiovascular medications — require dose reduction or interval adjustment based on CrCl. The Cockcroft-Gault equation is the standard formula used for this purpose.
CrCl (creatinine clearance) calculated by Cockcroft-Gault is used for drug dosing because most clinical drug trials used this method. eGFR (estimated GFR) calculated by MDRD or CKD-EPI is used for CKD staging and monitoring kidney disease progression. Although the values are often similar, they are not interchangeable for drug dosing decisions.
Women have proportionally less muscle mass than men and therefore produce less creatinine from muscle metabolism. Since serum creatinine is used as the surrogate for kidney function, the Cockcroft-Gault formula applies a correction factor of 0.85 for females to account for this difference. Without the correction, CrCl would be overestimated in women.
For obese patients (actual body weight > 1.3× IBW), use Adjusted Body Weight (ABW = IBW + 0.4 × (actual − IBW)). Using actual body weight in obese patients overestimates CrCl because adipose tissue does not produce creatinine proportionally. ABW corrects for the partial contribution of excess weight to drug distribution and clearance.
Use actual body weight if it is less than or equal to IBW. Use IBW if actual weight is only slightly above IBW (up to 1.3× IBW). Use Adjusted Body Weight (ABW) if actual weight exceeds 1.3× IBW or BMI is greater than 30. This calculator automatically determines the correct weight when height is provided.
The threshold varies by medication. Common adjustment thresholds are CrCl < 50 mL/min (e.g., metformin, many antibiotics), < 30 mL/min (e.g., direct oral anticoagulants like apixaban), and < 15 mL/min (near end-stage renal disease). Always verify the specific threshold in the current prescribing information or a clinical pharmacology database for each drug.

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