A 65-year-old man, 80 kg, creatinine 1.2 mg/dL
Cockcroft-Gault gives roughly 78 mL/min, in the mildly-decreased (G2) range.
Creatinine clearance & eGFR calculator (Cockcroft-Gault, CKD-EPI)
For healthcare professional reference only. This estimates kidney function from a formula — it is not a diagnosis and does not replace laboratory-confirmed testing, clinical judgement or a treating clinician’s assessment. Never adjust or stop a medication based solely on this result.
Result
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How it works
Creatinine is a waste product filtered out by the kidneys at a fairly constant rate from muscle metabolism; when kidney function declines, creatinine builds up in the blood. Both equations work backward from a measured serum creatinine level, plus age and sex (which affect typical muscle mass and creatinine production), to estimate how fast the kidneys are actually filtering blood.
Cockcroft-Gault was developed in 1976 and estimates creatinine clearance directly in mL/min, using body weight as a proxy for muscle mass — which is also its main weakness, since it was validated before obesity was as common and can overestimate function in overweight patients.
CKD-EPI (the 2021 version used here) instead estimates the glomerular filtration rate normalised to a standard body surface area, and does not need a weight input. It has replaced the older MDRD and race-adjusted CKD-EPI equations in most current clinical guidelines after that race coefficient was found to be unjustified and was removed.
Formulas used
Cockcroft-Gault
CrCl = [(140 − age) × weight(kg)] / (72 × Scr(mg/dL)) × (0.85 if female)
2021 CKD-EPI creatinine (race-free)
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age × (1.012 if female)
- κ
- 0.7 for women, 0.9 for men
- α
- −0.241 for women, −0.302 for men
Worked examples
The same patient by CKD-EPI
The race-free 2021 CKD-EPI equation gives an eGFR in a broadly similar range, without needing a weight value.
Assumptions and limits
- Both equations assume a stable (non-acutely-changing) creatinine level; they are unreliable during rapidly changing kidney function (acute kidney injury).
- Serum creatinine is assumed measured by a standardised (IDMS-traceable) laboratory assay, as both equations were calibrated against that standard.
Frequently asked questions
Why do the two equations give different numbers for the same patient?
They were derived from different populations with different statistical methods, and Cockcroft-Gault reports an un-normalised clearance while CKD-EPI reports a rate normalised to 1.73 m² of body surface area. Neither is "more correct" in an absolute sense — clinical guidelines specify which to use for which purpose (e.g. many drug-dosing references still specify Cockcroft-Gault because that is what was used in the original dosing studies).
Can I use this to adjust a medication dose myself?
No. This estimates kidney function only. Dose adjustment for renal impairment depends on the specific drug, its therapeutic range, and the prescribing information or a pharmacist’s guidance — never adjust or stop a medication based solely on a number from this page.
Updated