Creatinine clearance: frequently asked questions

CrCl (mL/min) = [(140 − age) × weight in kg] / (72 × serum creatinine in mg/dL), multiplied by 0.85 for females. This is the Cockcroft-Gault equation (Cockcroft & Gault, Nephron 1976). Which weight you use matters: ideal body weight for normal-weight patients, adjusted body weight when BMI is 30 or above.

Estimated CrCl is calculated from four variables — age, sex, body weight and serum creatinine — using Cockcroft-Gault. It is an estimate of clearance, not a measurement. Measured creatinine clearance requires a timed urine collection, which this site calculates separately.

Divide [(140 − age) × weight in kg] by (72 × serum creatinine in mg/dL), then multiply by 0.85 for females. If your laboratory reports creatinine in µmol/L, divide by 88.4 to convert to mg/dL first — or switch the unit toggle above and the calculator does it for you.

Scr is serum creatinine, the denominator of the Cockcroft-Gault equation: CrCl = [(140 − age) × weight] / (72 × Scr). Because Scr sits in the denominator, small changes at low creatinine values produce large changes in estimated clearance — the relationship is curvilinear, not linear.

The Cockcroft-Gault equation is CrCl (mL/min) = [(140 − age) × weight(kg)] / (72 × Scr in mg/dL), × 0.85 if female. In SI units it is [(140 − age) × weight(kg) × 1.23] / Scr in µmol/L for males, and × 1.04 for females. Published in Nephron, 1976.

Enter your age, sex, weight and most recent serum creatinine into the calculator above and the result appears immediately. Note that Cockcroft-Gault was designed for clinician use in drug dosing, not for self-assessment — discuss any result with a healthcare professional before acting on it.

Subtract age from 140, multiply by body weight in kilograms, divide by 72 times serum creatinine in mg/dL, then multiply by 0.85 for females. Choose the weight basis before you start: actual weight if below ideal, ideal weight at normal BMI, adjusted weight if BMI is 30 or above.

Use actual body weight if the patient weighs less than their ideal body weight, ideal body weight at a normal BMI, and adjusted body weight (IBW + 0.4 × [actual − IBW]) when BMI is 30 or above. This is convention rather than a validated equation, and institutional protocol takes precedence.

You cannot convert directly — they are different measures. eGFR is reported per 1.73 m² of body surface area; CrCl is not. To make them roughly comparable, de-index eGFR by multiplying by the patient’s BSA and dividing by 1.73. Even then, use CrCl for drug dosing where the label specifies it.

The same de-indexing applies: CrCl-equivalent ≈ eGFR × BSA / 1.73. Note that creatinine clearance systematically exceeds true GFR, because creatinine is both filtered and actively secreted by the renal tubules. The two figures are not interchangeable even after conversion.

Index the CrCl to body surface area: multiply by 1.73 and divide by the patient’s BSA. This puts it in the same units as eGFR but does not make it an eGFR — tubular secretion of creatinine means clearance overestimates true GFR, typically by 10–20%.

CKD-EPI estimates glomerular filtration rate in mL/min/1.73 m². The 2021 creatinine version is eGFR = 142 × min(Scr/κ,1)^α × max(Scr/κ,1)^−1.200 × 0.9938^age × 1.012 if female, where κ is 0.7 for females and 0.9 for males (Inker et al., NEJM 2021). It contains no race coefficient.

eGFR = 133 × min(Scys/0.8,1)^−0.499 × max(Scys/0.8,1)^−1.328 × 0.996^age × 0.932 if female, with cystatin C in mg/L (Inker et al., NEJM 2012). Cystatin C is less affected by muscle mass than creatinine, which makes it useful where creatinine is unreliable.

Yes, for most purposes. CKD-EPI is more accurate at higher GFR values, where MDRD systematically underestimates. The 2021 CKD-EPI equations also removed the race coefficient that MDRD retains. MDRD is included on this page only for comparison with historical results.

90 mL/min/1.73 m² or above is KDIGO category G1, described as normal or high. However, eGFR alone does not diagnose chronic kidney disease — KDIGO staging combines the GFR category with albuminuria and requires abnormalities to persist for at least three months.

By GFR category and albuminuria together (KDIGO 2012). GFR categories run G1 (≥90) through G5 (<15) in mL/min/1.73 m², with G3 split into G3a (45–59) and G3b (30–44). Both must persist for three months or more for a chronic kidney disease diagnosis.