Cockcroft-Gault Equation

Q: When should I use Cockcroft-Gault instead of CKD-EPI?

Use Cockcroft-Gault when adjusting medication doses, as many drug labels still reference CrCl from this equation.

Q: What weight should I use in the Cockcroft-Gault equation?

Use actual body weight by default. Adjusted body weight may be used in obese patients per institutional guidelines.

Estimates creatinine clearance (CrCl) for medication dosing using the Cockcroft-Gault equation.

Nephrology Internal MedicineEvidence-BasedUpdated 2026-08-06

Clinical decision-support tool for qualified healthcare professionals. Results are not a diagnosis and should not replace professional clinical judgment.

Clinical Notes

The Cockcroft-Gault equation estimates creatinine clearance (CrCl) from age, weight, sex, and serum creatinine. It was the first widely adopted method for estimating renal function before direct GFR measurement became practical, and it remains embedded in many medication dosing guidelines. The equation outputs an absolute CrCl in mL/min using actual body weight, adjusted for sex. The estimated creatinine clearance should not be equated with measured GFR or with eGFR reported by MDRD or CKD-EPI. Those equations report GFR normalized to body surface area (mL/min/1.73m2), whereas Cockcroft-Gault outputs an absolute clearance (mL/min). Different equations also require different serum creatinine units (notably mg/dL versus micromol/L); for the standard form of this equation, creatinine must be entered in mg/dL. Converting from micromol/L requires dividing by 88.4 before entry. The estimate is most reliable in adults with stable renal function and body weight near the population average. It becomes progressively less accurate at extremes of body size, in the very old or very young, with impaired muscle mass, amputation, pregnancy, ascites, severe edema, or rapidly changing renal function. Patients with significantly abnormal weight should have dosing decisions cross-referenced against the specific equation recommended in the source guideline. This estimate supports clinical decision-making in a medication dosing context and is not a diagnosis of kidney disease. Transplant recipients, patients with unusual body composition, or anyone with rapidly changing creatinine should have dosing confirmed against the guideline-appropriate equation. Specialist review may be warranted when the result is discordant with the clinical picture.

Calculator Information

Specialty

Internal Medicine

📋 Reference Ranges

Normal Range

90–120 mL/min

Reference ranges for this calculator
Classification	Range
Normal renal function	≥90
Mild renal impairment	60–89
Moderate renal impairment	30–59
Severe renal impairment	15–29
Kidney failure	<15

What This Calculator Measures

Estimates creatinine clearance (CrCl) to guide drug dosing adjustments, particularly for renally cleared medications.

How to Use

Enter the patient's age, weight (kg), and serum creatinine (mg/dL).
Select the patient's sex.
Review the estimated creatinine clearance.

How the Calculation Works

Creatinine clearance is estimated as CrCl = ((140 - age) x weight) / (72 x serum creatinine), multiplied by 0.85 for females. Weight is in kg and creatinine in mg/dL.

Variables Explained

Age

Age in years, subtracted from 140 in the numerator.

Weight

Body weight in kilograms used in the numerator.

Sex

Biological sex; females receive a 0.85 correction factor.

Serum Creatinine

Serum creatinine in mg/dL, used in the denominator.

Interpretation Guide

CrCl >90 mL/min is normal. 60–89 is mildly decreased. 30–59 is moderately decreased. 15–29 is severely decreased. <15 indicates kidney failure. Use the result to adjust medication doses per drug-specific guidance.

Sex-specific interpretationAge-specific interpretation

Clinical Significance

The Cockcroft-Gault equation remains the most widely referenced method for drug dosing adjustments in renal impairment, as most drug labeling and pharmacokinetic studies used this equation for dose adjustments.

When It Is Useful

Drug dosing for renally cleared medications (many antibiotics, anticoagulants, diabetes medications)
Situations where a medication label specifically requires Cockcroft-Gault CrCl
When eGFR-based dosing is not specified in drug labeling

When It Is Not Useful

For CKD staging (use CKD-EPI eGFR instead)
In patients with rapidly changing renal function (use actual measured CrCl or consider real-time eGFR)
As a precise measure of GFR — it is an estimate

Common Mistakes

Entering creatinine in micromoles per liter without dividing by 88.4, since the equation expects mg/dL.
Comparing the mL/min result directly with a body-surface-area-normalized eGFR as if they were the same scale.
Calculating a dose estimate while renal function is rapidly changing, where the steady-state assumption fails.

Limitations

Uses estimated rather than measured creatinine clearance.
Weight choice matters: actual, ideal, or adjusted body weight may be appropriate depending on clinical context.
Less accurate in obesity, extreme muscle mass, amputees, and unstable renal function.
Many drug dosing guidelines still reference Cockcroft-Gault despite its age.

Worked Example

A 70-year-old man weighing 75 kg has a serum creatinine of 1.4 mg/dL.

Inputs:

age: 70

weight: 75

creatinine: 1.4

sex: 1

Expected Result: CrCl ≈ (140 − 70) × 75 / (72 × 1.4) ≈ 52.1 mL/min. This indicates moderate renal impairment and may require dose adjustment for renally cleared drugs.

Evidence & References

Source:: Nephrology / Pharmacy
Content updated:: 2026-08

Cockcroft DW, Gault MH. Nephron. 1976;16:31-41.

References

Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron. 1976;16:31-41. (Original Description)

Frequently Asked Questions

When should I use Cockcroft-Gault instead of CKD-EPI?

Use Cockcroft-Gault when adjusting medication doses, as many drug labels still reference CrCl from this equation.

What weight should I use in the Cockcroft-Gault equation?

Use actual body weight by default. Adjusted body weight may be used in obese patients per institutional guidelines.

Disclaimer: This calculator is intended for educational and clinical decision support purposes only. Drug dosing decisions should always consider the individual patient's clinical context and current drug labeling.