ganak.appCreatinine Clearance Calculator
Calculate creatinine clearance (CrCl) using the Cockcroft-Gault equation with automatic ideal body weight (IBW) and adjusted body weight (ABW) selection. Includes renal function classification (normal, mild, moderate, severe impairment) and drug dosing thresholds. Supports mg/dL and µmol/L. Free, instant results calculated in your browser.
Enables automatic IBW / ABW body weight selection.
IBW recommended — BMI within normal range.
creatinine clearance
Range
50–89 mL/min
Weight Used
IBW (65.9 kg)
Status
Mild Impairment
Body Weight Comparison
CrCl with actual, ideal, and adjusted body weights
Actual Body Weight
92.4mL/min
Ideal Body Weight (IBW)65.9 kgActive
87.0mL/min
IBW (Devine formula) is recommended for normal BMI. ABW is used when BMI ≥ 25 and actual weight exceeds IBW.
Renal Function & Drug Dosing
How CrCl guides medication dose adjustments
Mild Impairment: 50–89 mL/min
Mildly reduced kidney function. Common in older adults.
Drug dosing: Monitor renal function. Some medications require dose adjustment or interval extension.
| CrCl | Category |
|---|---|
| ≥ 90 mL/min | Normal |
| 50–89 mL/min | Mild Impairment← you |
| 30–49 mL/min | Moderate Impairment |
| 10–29 mL/min | Severe Impairment |
| < 10 mL/min | Kidney Failure |
This calculator is for educational purposes only and is not a substitute for professional medical or pharmacist advice. Creatinine clearance estimates assume stable renal function. Body weight selection (IBW/ABW) reflects common pharmacokinetic practice — some drug labels specify actual body weight regardless of BMI; always consult current prescribing information. Verify all dosing decisions with a qualified clinician or pharmacist.
What is Creatinine Clearance?
The Cockcroft-Gault equation and its clinical purpose
Creatinine clearance (CrCl) estimates the rate at which the kidneys filter creatinine — a waste product of muscle metabolism — from the blood, expressed in mL/min. It is a widely used metric for adjusting medication doses in patients with reduced kidney function, particularly when drug labels specify the Cockcroft-Gault method.
Drug dose adjustments
Many drug labels specify CrCl (label-dependent)
Kidney function estimate
From a simple blood test
Pharmacokinetics
Predicts drug elimination rate
CrCl is not the same as eGFR. Many drug prescribing labels reference Cockcroft-Gault CrCl for dose adjustments, but FDA does not mandate a single estimating equation — individual labels may use measured CrCl, MDRD, or CKD-EPI instead. Always confirm which method the specific drug label uses before making dosing decisions.
Cockcroft-Gault Formula
Published by Cockcroft & Gault in Nephron (1976)
Patient age in years — CrCl falls ~1 mL/min per year after age 40
Body weight in kg — use actual, IBW, or ABW based on BMI
Serum creatinine in mg/dL — assumes stable renal function
Female sex factor — women have less muscle mass per unit weight
The (140 − Age) term means CrCl naturally decreases with age, even with a stable serum creatinine — reflecting the normal decline in kidney function of roughly 1 mL/min per year after age 40.
Which Body Weight to Use
IBW, ABW, or actual weight — and why the choice matters
The original Cockcroft-Gault study was conducted in non-obese patients using actual body weight. In obese patients, excess adipose tissue does not contribute proportionally to creatinine production — so using actual weight may overestimate CrCl, increasing the risk of drug accumulation. However, some drug labels specify actual body weight; always verify with current prescribing information.
Underweight
BMI < 18.5 or Actual < IBW
Normal BMI
18.5–24.9
Overweight / Obese
BMI ≥ 25
This calculator automatically selects the recommended weight type when height is entered, based on your BMI. When IBW or ABW applies, you can override the selection using the Weight Used for CrCl selector — or check your drug label, as some agents specify actual body weight regardless of BMI.
Creatinine Clearance vs eGFR
Two metrics, two different clinical purposes — not interchangeable
Both CrCl and eGFR reflect kidney filtration, but they are calculated differently and serve distinct roles in clinical practice. Using the wrong metric when making dosing decisions can lead to under- or over-dosing.
Use our eGFR Calculator for CKD staging and disease monitoring. Use this CrCl Calculator when a drug label specifically references Cockcroft-Gault CrCl.
Note: FDA's 2024 renal-impairment pharmacokinetic guidance and NKF recommendations increasingly favour eGFR-based approaches for newer drug approvals. Always verify which equation the specific drug label you are consulting requires.
Limitations of the Cockcroft-Gault Equation
When the formula is less accurate and what to do instead
Stable renal function required
Acutely rising or falling creatinine invalidates the formula. Use measured CrCl from 24-hour urine in unstable patients.
Obesity overestimation
Actual body weight overestimates CrCl in obese patients because adipose tissue contributes minimally to creatinine production. Use ABW.
Drug effects on creatinine
Trimethoprim and cimetidine competitively inhibit tubular creatinine secretion, raising serum creatinine without affecting true GFR, leading to falsely low CrCl estimates.
Special populations
Less accurate in severe muscle wasting (low creatinine → overestimated CrCl), pregnancy, amputees, and pediatric patients (use Schwartz equation instead).
Frequently Asked Questions
Common questions about creatinine clearance and the Cockcroft-Gault equation