Creatinine Clearance Calculator (Cockcroft-Gault)

The tool applies the Cockcroft-Gault equation, published by Donald Cockcroft and Henry Gault in 1976. It estimates creatinine clearance, a stand-in for how fast the kidneys clear a drug, from four values available at the bedside: age, sex, body weight and serum creatinine. It is the estimate that regulators and drug labels use as the basis for renal dose adjustment.

With serum creatinine in mg/dL, the equation is:

CrCl = (140 − age) × weight(kg) ÷ (72 × SCr mg/dL)  [× 0.85 if female]

Sri Lankan labs report creatinine in either mg/dL or µmol/L, so the calculator accepts both. When you enter µmol/L it converts first using the IFCC standard 1 mg/dL = 88.4 µmol/L, then applies the same formula. The equivalent direct SI form multiplies the numerator by 88.4 and divides by the µmol/L value; the calculator computes the result both ways and shows the second as a cross-check, so a conversion slip cannot pass silently.

The result is grouped into the general renal-impairment bands the U.S. FDA uses in its dosing guidance: 50 mL/min and above (usually no reduction), 30–49 (moderate impairment), 15–29 (severe impairment) and below 15 (kidney failure). These are population bands to orient dosing decisions, the actual reduction for any specific drug comes from that drug's label, not from the band alone.

One deliberate limitation: the 1976 equation uses actual body weight, which this tool applies. In lean or very tall patients actual weight can overestimate clearance, so many clinicians substitute ideal body weight; in obese patients an adjusted body weight is common. This version does not auto-select a weight, because doing so would make the result non-deterministic and harder to check, enter whichever weight your local protocol specifies. Cockcroft-Gault is also unreliable in acute kidney injury, pregnancy, amputees and at extremes of muscle mass, where a measured (timed urine) clearance is preferred.

• Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron 1976;16(1):31-41.
• U.S. FDA: Guidance for Industry: Pharmacokinetics in Patients with Impaired Renal Function
• National Kidney Foundation: GFR / creatinine reference and unit conversions

The formula, the 0.85 female factor and the 1 mg/dL = 88.4 µmol/L conversion were last cross-checked against these sources on 2026-07-10. The Cockcroft-Gault equation has never been revised.