Kidney function
Creatinine clearance calculator (Cockcroft-Gault)
Estimate creatinine clearance from age, sex, body weight, and serum creatinine using the Cockcroft-Gault equation, the formula much drug-dosing guidance is still written against.
Enter your values above to see your result and what it means.
Why an equation from 1976 is still in use
CKD-EPI eGFR is the current standard for staging chronic kidney disease, and it is more accurate. Cockcroft-Gault persists for a practical reason: the pharmacokinetic studies behind a great many drug labels were conducted using it, and the dosing thresholds printed on those labels refer to creatinine clearance calculated this way. Substituting an eGFR value into a label written for Cockcroft-Gault can shift a patient into the wrong dosing band, which is why prescribers and pharmacists still calculate it.
The weight question
The original equation used actual body weight, which is what this calculator asks for. In obesity that choice inflates the result, because fat tissue contributes weight without contributing much creatinine production, so guidance often favours ideal or adjusted body weight instead. There is no single agreed rule, which is why this calculator uses the original input and states the limitation rather than silently applying a body-weight model you cannot see. If body weight is well above the ideal range, treat the output as an overestimate and ask a pharmacist which weight their guidance specifies.
What can move the number without kidney function changing
Serum creatinine reflects muscle mass and turnover as well as filtration. Very muscular people run higher creatinine at normal kidney function, and people with low muscle mass, including many older and chronically ill patients, run lower creatinine and can have meaningfully worse kidney function than their number suggests. Creatine supplements, a large meat meal before the blood draw, and some medicines that block creatinine secretion without changing filtration will all shift the figure.
Frequently asked questions
Is creatinine clearance the same as eGFR?
No. Creatinine clearance from Cockcroft-Gault is reported in mL/min and uses body weight. CKD-EPI eGFR is reported in mL/min/1.73m² and is normalised to body surface area instead. The two numbers routinely differ, and the difference grows the further someone is from average body size. Kidney disease staging uses eGFR; drug dosing often specifies creatinine clearance.
Which weight should I enter?
This calculator uses actual body weight, matching the original equation. If your weight is well above the ideal range for your height, the result will be an overestimate of clearance, and a pharmacist may recalculate it using ideal or adjusted body weight according to the guidance for the specific drug.
My creatinine is in µmol/L. How do I convert it?
Divide the µmol/L value by 88.4 to get mg/dL. For example, 88 µmol/L is approximately 1.0 mg/dL.
Can I use this to decide my own medication dose?
No. This calculator reproduces a published formula for information, and dosing decisions depend on the specific drug, the indication, other medicines, and clinical factors this tool does not collect. Take the result to a prescriber or pharmacist rather than acting on it.