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.