Which body weight should I use in the Cockcroft-Gault equation?

Use actual body weight for non-obese patients. For patients whose actual weight exceeds ideal body weight (IBW) by more than 30%, many guidelines recommend adjusted body weight (AdjBW = IBW + 0.4 × [Actual − IBW]). This tool uses the weight you enter, so apply clinical judgment.

Why are the antibiotic tiers different for each drug?

Each antibiotic has unique pharmacokinetics. Vancomycin and gentamicin are primarily renally cleared and accumulate significantly in renal impairment, requiring large dose reductions. Piperacillin-tazobactam and meropenem also need adjustment but follow slightly different cutoffs per their package inserts.

Are these dosing recommendations definitive?

No. This tool is a clinical reference only. Dosing recommendations vary by indication, pathogen MIC, site of infection, and patient-specific factors. Always consult current prescribing information, a clinical pharmacist, or authoritative databases (Lexicomp, Micromedex) before finalizing a dose.

How accurate is Cockcroft-Gault compared to newer GFR equations?

The Cockcroft-Gault CrCl remains the standard referenced in most drug labeling and FDA guidance for dose adjustment because clinical trials were conducted using this equation. CKD-EPI eGFR is preferred for CKD staging but not universally validated for drug dosing.

What does a CrCl of 0 mean?

A CrCl near zero or negative (possible when age and creatinine are very high) indicates anuric or near-anuric kidney function consistent with dialysis-dependent renal failure. Use the dialysis row in the dosing table and consult nephrology.

Is patient data stored anywhere?

No. All calculations happen entirely in your browser. Nothing is sent to any server.

Creatinine Clearance for Antibiotic Dosing

Enter patient age, weight, sex, and serum creatinine to calculate CrCl, then see dose-adjustment tiers for vancomycin, gentamicin, pip-tazo, and meropenem.

Patient Parameters

Age *

years

Weight *

Biological Sex *

Male Female (×0.85)

Serum Creatinine *

Enter patient data and click Calculate.

Creatinine Clearance

mL/min

Dose-Adjustment Tiers

Antibiotic	≥50	25–49	10–24	<10	HD
	CrCl (mL/min)

Highlighted column = patient's current CrCl tier. Recommendations are general references only — verify against current prescribing information. HD = hemodialysis.

Summary

Enter patient age, weight, sex, and serum creatinine to calculate CrCl, then see dose-adjustment tiers for vancomycin, gentamicin, pip-tazo, and meropenem.

How it works

Enter the patient's age in years and body weight in kilograms or pounds.
Select biological sex — the formula multiplies by 0.85 for females to account for lower average muscle mass.
Enter serum creatinine in mg/dL or µmol/L; the tool converts automatically.
CrCl is calculated: [(140 − Age) × Weight(kg) × (0.85 if female)] ÷ (72 × SCr in mg/dL).
The result is matched against four CrCl tiers (≥50, 25–49, 10–24, <10 mL/min plus dialysis) to display antibiotic dosing recommendations.
Review the highlighted row for each antibiotic and confirm against current prescribing information before ordering.

Use cases

Quickly choosing an antibiotic dose when lab CrCl is not yet available.
Double-checking pharmacy recommendations at the bedside.
Teaching renal pharmacokinetics to medical students and residents.
Dosing antibiotics in patients with acute kidney injury or CKD.
Pre-rounding review in ICU or infectious disease rounds.
Adjusting empiric antibiotic coverage in sepsis protocols.
Screening patients before initiating aminoglycoside or glycopeptide therapy.
Reference during antibiotic stewardship program audits.

Frequently Asked Questions

Last updated: 2026-09-20 · Reviewed by Nham Vu