π§ͺ Creatinine Clearance Calculator
Cockcroft-Gault estimate from age, weight, sex, and creatinine.
Estimates only. Drug dosing adjustments must be verified by a pharmacist or clinician.
Creatinine clearance estimates how fast the kidneys filter blood, and drug dosing lives or dies by it. The Cockcroft-Gault equation, published in 1976, predicts clearance from age, weight, sex, and serum creatinine, and pharmacists still use it for dosing decisions even in the eGFR era. Enter your values for the estimate plus the CKD stage it implies.
How to Use This Calculator
Enter age, weight, sex, and serum creatinine in mg/dL. The clearance and CKD stage appear.
Use a stable creatinine: the formula assumes steady state, not rapidly changing kidney function.
Enter actual body weight. In significant obesity, clinicians may use adjusted body weight; note the assumption.
Read the mL/min value and the CKD stage. Drug dosing adjustments typically start below 60.
The Cockcroft-Gault Equation
The equation's logic: creatinine production falls with age (less muscle) and rises with weight (more muscle), while serum creatinine inversely reflects clearance. The 72 folds unit conversions and the original regression constant together; the 0.85 adjusts for women's lower muscle mass. Cockcroft and Gault derived it from 249 patients with measured clearances, and it has survived 50 years because the physiology it encodes is sound, even though modern eGFR equations (CKD-EPI) estimate filtration more accurately for staging.
Why pharmacists still prefer it: drug dosing trials were conducted in the Cockcroft-Gault era, so FDA labels reference CrCl by this equation. Using CKD-EPI eGFR for dosing can give a different number than the label studied, which is why pharmacy systems keep both. For pure kidney staging, eGFR wins; for dosing, Cockcroft-Gault remains the lingua franca.
Worked Example
A 65-year-old man, 70 kg, creatinine 1.1 mg/dL. CrCl = (140-65) x 70 / (72 x 1.1) = 5250 / 79.2 = 66.3 mL/min: stage G2, mild decrease. A woman with identical numbers: x 0.85 = 56.3 mL/min, stage G3a, crossing the threshold where many drugs need dose review. Same labs, different dosing implications, which is why the sex factor matters. Now the same man at creatinine 2.2: 33.1 mL/min, stage G3b, where most renally cleared drugs need adjustment.
Drug Dosing: Where This Number Rules
Antibiotics (many cephalosporins, vancomycin, aminoglycosides), anticoagulants (DOACs have CrCl-based dosing bands), diabetes drugs (metformin contraindicated below 30), and chemotherapy (carboplatin via Calvert uses GFR directly) all pivot on clearance. The pattern: below 60, review; below 30, adjust most; below 15, nephrology co-manages. Our BUN/creatinine ratio helps sort why clearance fell (prerenal vs intrinsic), which changes management beyond dosing.
Creatinine's blind spot deserves repeating: it does not rise until about half of kidney function is lost, because the kidneys hyperfilter and muscle mass varies. A muscular 30-year-old and a frail 80-year-old with the same creatinine 1.2 have very different clearances, which the equation captures through age and weight. In rapidly changing AKI, no estimating equation works: the creatinine lags reality by a day or more, and measured clearance or clinical judgment takes over.
Protecting Kidney Function
Control blood pressure and blood sugar: they are the top two CKD drivers. Avoid NSAIDs when alternatives exist, especially with dehydration. Stay hydrated but do not overdo water to "flush" kidneys; the evidence for that is thin. Review medications with your pharmacist for nephrotoxins. And track the trend: a CrCl drifting from 80 to 65 over five years tells a different story than a stable 65. The number on this page is a snapshot; the slope is the diagnosis.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is the Cockcroft-Gault equation?
CrCl = ((140 - age) x weight in kg) / (72 x serum creatinine) x 0.85 if female. Published in 1976, it estimates creatinine clearance for drug dosing. Pharmacists still prefer it because drug labels were studied with it.
What is a normal creatinine clearance?
Roughly 90-120 mL/min in healthy young adults, declining with age. Below 60 suggests chronic kidney disease; below 30 severe; below 15 kidney failure. This calculator shows the CKD stage with your result.
What is the difference between CrCl and eGFR?
CrCl (Cockcroft-Gault) estimates creatinine clearance and remains the drug-dosing standard. eGFR (CKD-EPI) estimates filtration rate normalized to body surface and is better for CKD staging. Labs report eGFR; pharmacists compute CrCl.
Why do women multiply by 0.85?
Because women average less muscle mass than men at the same weight, producing less creatinine. Without the factor, the equation would overestimate their clearance. It is a population average, imprecise for very muscular or frail individuals.
Can I use ideal body weight in Cockcroft-Gault?
In significant obesity, many clinicians use adjusted body weight (IBW + 0.4 x (actual - IBW)) to avoid overestimation, since fat produces little creatinine. Practice varies by institution; note which weight you used.
Does creatinine clearance change with age?
Yes, declining about 1 mL/min per year after 40 as muscle mass and nephron number fall. The (140 - age) term encodes this. An 80-year-old with "normal" creatinine often has meaningfully reduced clearance.
What drugs need dose adjustment in kidney disease?
Many: certain antibiotics, DOAC anticoagulants, metformin (avoid below 30), allopurinol, gabapentin, and chemotherapy agents. Pharmacists check renally cleared drugs against CrCl routinely; always keep an updated medication list.
Why is my eGFR different from Cockcroft-Gault?
They are different equations with different purposes: eGFR (CKD-EPI) is normalized to 1.73 m2 body surface for staging; CrCl is absolute mL/min for dosing. Expect them to differ, especially at body-size extremes.
Can dehydration affect creatinine clearance estimates?
Yes. Volume depletion raises creatinine and lowers the estimate (prerenal pattern), which usually reverses with fluids. The equation assumes steady state; in acute illness with changing creatinine, no estimate is reliable.
How can I protect my kidney function?
Control blood pressure and blood sugar, avoid NSAIDs when possible, stay reasonably hydrated, avoid smoking, and review medications for nephrotoxins with your pharmacist. Track the trend over years, not single readings.