# Creatinine Clearance Calculator — Cockcroft-Gault (Drug Dosing)
> Free Cockcroft-Gault creatinine clearance calculator — the formula FDA labels reference for renal drug-dose adjustment. Returns CrCl in mL/min with the sex correction applied.

## Overview

The Cockcroft-Gault equation estimates creatinine clearance from age, weight, and serum creatinine. Although CKD-EPI 2021 is the preferred equation for chronic kidney disease staging, the FDA continues to reference Cockcroft-Gault on most drug labels for renal-dose adjustment. Cockcroft-Gault returns CrCl in mL/min (not normalised to body surface area), with a 0.85 multiplier for female sex from the original 1976 derivation. Clinically, the equation underperforms in obesity, oedema, and at extremes of muscle mass; the corresponding CKD-EPI eGFR or measured CrCl may be more reliable in those settings.

## Who this is for

- Pharmacists and clinicians dosing renally cleared medications
- Internal medicine residents
- Hospitalists and nephrology consult services

## How to interpret the result

| Score / band | Meaning |
|---|---|
| ≥ 60 | Most renally cleared drugs require no adjustment unless the label specifies otherwise. |
| 30–59 | Moderate impairment — many drug labels specify dose reduction or interval extension. |
| 15–29 | Severe impairment — commonly large dose reductions or alternative agents. |
| < 15 / dialysis | Specific dialysis-aware dosing protocols apply. |

## Cited source

**FDA Pharmacokinetics in Patients with Impaired Renal Function — Industry Guidance** (2020) — U.S. Food and Drug Administration

_Primary publication:_ Cockcroft DW, Gault MH. Nephron 1976

## FAQs

### Why does the FDA still use Cockcroft-Gault?

Cockcroft-Gault was used in the pivotal pharmacokinetic studies of most marketed drugs, so the FDA references it on labels for consistency. Newer equations (CKD-EPI) may give different bands and shift dose categories.

### Should I use actual, ideal, or adjusted body weight?

The original derivation used actual body weight. For obese patients, many institutional pharmacies use ideal or adjusted body weight to avoid overestimating CrCl. Verify with your pharmacy.

### Cockcroft-Gault vs eGFR — which gives a higher number?

Generally, Cockcroft-Gault (mL/min) and eGFR (mL/min/1.73 m²) are similar in average-sized adults but diverge at extremes of body size because eGFR is BSA-normalised.

### Is Cockcroft-Gault reliable in AKI?

No. Both Cockcroft-Gault and eGFR assume steady-state creatinine. In AKI, neither is reliable; clinical judgement and direct measurement (timed urine collection) may be needed.

### Should pharmacists round Cockcroft-Gault to a category?

Many institutional protocols round to FDA-label categories (e.g. CrCl ≥ 60, 30–59, 15–29, < 15) rather than treating the number as exact. Verify your institutional convention.

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_Rounds AI is a citation-first clinical AI assistant. It supports clinical reasoning by surfacing cited information and is not a substitute for independent clinical judgement._