Creatinine clearance calculator

Published by Cockcroft and Gault in 1976, the formula estimates creatinine clearance in mL/min as (140 − age) × weight (kg) × sex factor ÷ (72 × serum creatinine in mg/dL), where the sex factor is 1.0 for men and 0.85 for women. It predates newer eGFR equations such as CKD-EPI, but remains a standard reference formula for renal drug dosing in UK and US formularies, since much of the existing dosing evidence base was originally derived against it. This calculator accepts creatinine in either µmol/L or mg/dL and converts automatically.

Cockcroft-Gault was derived using actual body weight, which can overestimate clearance in patients who carry excess weight relative to height. This calculator also reports the result using ideal body weight (Devine formula, from height) and, where actual weight exceeds ideal body weight by more than 20%, an adjusted body weight (ideal weight plus 40% of the excess) — the approach commonly used when making renal drug dosing decisions in overweight or obese patients. Leave height blank to see actual-weight CrCl alone.

Cockcroft-Gault is a population-derived estimate, not a direct measurement of kidney function, and can be less reliable at extremes of body weight, in acute kidney injury, oedema, amputees, or where muscle mass is unusually low or high. Unlike CKD-EPI-based eGFR, it has no correction for body surface area. This tool is for reference only and is not a substitute for clinical judgement — dosing and management decisions remain with the treating clinician and should be checked against current local formulary guidance.