Creatinine Clearance Calculator

Cockcroft-Gault, the standard for renal drug dosing.

Calculate creatinine clearance using the Cockcroft-Gault equation, the formula most drug labels specify for renal dose adjustment.

Written and maintained by Mohit PatelLast checked August 4, 2026How we build these

Sex

Age

years

Weight

Ideal or adjusted body weight is usually preferred over actual weight in obesity.

Serum creatinine

mg/dL

Which weight you enter materially changes the result and is the most common source of error. Follow local pharmacy guidance for the drug being dosed.

Creatinine clearance (Cockcroft-Gault)

78 mL/min

Mildly reduced

Age factor (140 − age)80

Sex multiplier1.00

Serum creatinine1 mg/dL

Weight used70 kg

Cockcroft-Gault is not normalised to body surface area, so it is not interchangeable with eGFR. Use eGFR for staging, this for dosing.

How the Creatinine Clearance Calculator works

Cockcroft-Gault estimates creatinine clearance from serum creatinine, age, weight and sex. It is older and less accurate than modern eGFR equations for staging kidney disease, but it remains the formula most drug labels were written against, so it is still the one used for dose adjustment.

Also known as: CrCl calculator · Cockcroft Gault equation · kidney clearance calculator

The Cockcroft-Gault equation

Published in 1976, Cockcroft-Gault estimates creatinine clearance from age, weight, sex and serum creatinine. For men: 140 minus age, times weight in kilograms, divided by 72 times serum creatinine in milligrams per decilitre. For women the result is multiplied by 0.85.

It was derived from 249 men, and the female correction factor was applied without a female derivation cohort. That is a substantial limitation for an equation still in widespread use.

It estimates creatinine clearance rather than glomerular filtration rate. Creatinine is both filtered and secreted by the tubules, so clearance overestimates true GFR by roughly 10% to 20%.

Which weight to use

The equation was derived using actual body weight, and using actual weight in obesity substantially overestimates clearance, because adipose tissue does not produce creatinine in proportion to its mass.

Common practice uses ideal body weight in obesity, or adjusted body weight, and the choice varies between institutions and between drugs.

That variation is a real source of inconsistency. The same patient can have a clearance estimate differing by 50% depending on which weight was used, which matters enormously when the figure is being used to dose a drug with a narrow therapeutic window.

Why it survives despite better equations

Newer equations, particularly CKD-EPI, estimate GFR more accurately and are what laboratories report.

Cockcroft-Gault persists in drug dosing because the pharmacokinetic studies that established dosing recommendations used it. Switching to a different estimate changes the relationship between the calculated number and the dosing evidence.

So the correct equation depends on the purpose. For staging kidney disease, use the reported eGFR. For dosing a drug whose label specifies creatinine clearance, use Cockcroft-Gault, because that is what the label was validated against.

Where the estimate fails

Any condition that changes creatinine production independently of kidney function distorts it. Very high or very low muscle mass, amputation, malnutrition, and severe liver disease all do.

Acute kidney injury is the important case. Creatinine takes time to accumulate after filtration falls, so in rapidly changing kidney function the serum creatinine lags reality by a day or more, and any estimate based on it is describing yesterday.

Several drugs, including trimethoprim and cimetidine, inhibit tubular creatinine secretion. They raise serum creatinine without changing GFR, which makes the estimate falsely low.

The boundary of this page

This performs a calculation. It does not know which weight your protocol specifies, whether the creatinine is stable, what drug is being dosed, or anything else about the patient.

Renal dosing decisions are made by prescribers and pharmacists with access to the full record and to the specific drug's guidance, and they are checked. That process exists because the consequences of getting it wrong run in both directions: toxicity from overdose and treatment failure from underdose.

For anyone reading their own results, an eGFR figure on a blood test is interpreted by the doctor who ordered it, in the context of everything else they know. A number calculated here in isolation is not a diagnosis and should not be treated as one.

Where to go next

The Creatinine Clearance question rarely arrives on its own. These are the ones that usually come with it:

eGFR Calculator — CKD-EPI 2021, without the race coefficient.
Adjusted Body Weight Calculator — Ideal, actual and adjusted weight for dosing.
Body Surface Area Calculator — BSA by Du Bois, Mosteller, Haycock and Boyd.
BMI Calculator — Body mass index with category and healthy weight range.

Sources

Cockcroft & Gault, Nephron 1976 (PubMed)

Not medical advice. This calculator gives a general estimate, not medical advice. It cannot account for your individual health, medical history, or medication. Talk to a qualified healthcare professional before acting on any result.

Frequently asked questions

What is the Cockcroft-Gault equation?

CrCl = ((140 − age) × weight in kg) ÷ (72 × serum creatinine in mg/dL), multiplied by 0.85 for women. It was published in 1976 from a sample of 249 patients, almost all male.

Which weight should I use in Cockcroft-Gault?

This is the most common source of error. Actual body weight overestimates clearance in obesity; most references recommend ideal body weight, or adjusted body weight when the patient is more than about 30% above ideal. Follow local pharmacy guidance.

Cockcroft-Gault or eGFR?

Use eGFR (CKD-EPI) to stage chronic kidney disease, and Cockcroft-Gault for drug dosing unless the label specifies otherwise. They are not interchangeable: eGFR is normalised to body surface area and Cockcroft-Gault is not, so they can differ substantially in people at either extreme of size.

What limits its accuracy?

Serum creatinine depends on muscle mass, so it overestimates function in frail or elderly patients with low muscle and underestimates it in muscular ones. It is also unreliable when kidney function is changing rapidly, since creatinine lags behind.