What is the Cockcroft-Gault formula?

CrCl (mL/min) = [(140 − Age) × Weight(kg)] ÷ (72 × SCr in mg/dL). For females, multiply by 0.85. This 1976 equation remains the standard for drug dosing because most clinical trials and drug labeling reference it directly.

When should I use ideal or adjusted body weight instead of actual?

For patients whose actual weight exceeds ideal body weight (IBW) by more than 30%, many guidelines recommend IBW or adjusted body weight (AdjBW = IBW + 0.4 × [Actual − IBW]). Using actual weight in obese patients can overestimate CrCl and lead to drug toxicity. This tool calculates all three so you can compare.

How is ideal body weight calculated here?

IBW uses the Devine formula: males = 50 + 2.3 × (height in inches − 60); females = 45.5 + 2.3 × (height in inches − 60). Height input is required when IBW or adjusted body weight is selected.

Why does CrCl differ from eGFR (CKD-EPI)?

CrCl (Cockcroft-Gault) slightly overestimates GFR due to tubular secretion. For drug dosing, CrCl remains preferred because it is what was used in drug studies. For CKD staging and population-level risk, eGFR from CKD-EPI is the standard.

What do the dosing tiers mean?

Standard tiers map to CrCl ranges: ≥60 mL/min = normal or mild, 30–59 = moderate impairment, 15–29 = severe impairment, and <15 (or dialysis) = kidney failure. Exact cutoffs vary by drug — always confirm against the prescribing information.

Is this tool a substitute for clinical judgment?

No. This tool is for educational and reference use only. Dosing decisions must account for indication, pathogen, drug interactions, and individual patient factors. Always consult current prescribing information or a clinical pharmacist.

Creatinine Clearance for Drug Dosing

Name: Creatinine Clearance for Drug Dosing
Availability: InStock
Author: Nham Vu

Enter age, weight, sex, and serum creatinine to compute CrCl via Cockcroft-Gault and see which renal impairment tier applies for drug dosing.

Patient Parameters

Age (years)

Weight Type

Actual Weight

Serum Creatinine

Biological Sex

Male Female

For educational use only. Not a substitute for clinical judgment.

Fill in patient data and press Calculate.

Summary

Enter age, weight, sex, and serum creatinine to compute CrCl via Cockcroft-Gault and see which renal impairment tier applies for drug dosing.

How it works

Enter the patient's age in years, body weight, and serum creatinine level.
Select the appropriate weight type: actual body weight for non-obese patients, ideal body weight for obese patients per many guidelines, or adjusted body weight (IBW + 0.4 × excess) for patients significantly above IBW.
Select biological sex — the formula multiplies by 0.85 for females to account for lower average muscle mass.
Choose serum creatinine units (mg/dL or µmol/L); the tool converts automatically.
CrCl is computed: [(140 − Age) × Weight(kg)] ÷ (72 × SCr in mg/dL) × (0.85 if female).
The result is displayed in mL/min alongside the matched dosing impairment tier and clinical interpretation.

Use cases

Selecting an appropriate dose for renally cleared drugs before ordering.
Determining which renal dosing tier applies when drug labeling references CrCl thresholds.
Adjusting weight input method for obese patients using IBW or adjusted body weight.
Verifying pharmacy dosing recommendations at the bedside.
Teaching Cockcroft-Gault pharmacokinetics in clinical pharmacology courses.
Pre-rounding renal function review in hospital or ICU settings.
Screening patients for drugs contraindicated below specific CrCl cutoffs.
Converting serum creatinine from µmol/L (SI) to mg/dL for the formula.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu