My Easy Science
Renal Dose Helper
Cockcroft-Gault creatinine clearance, with a units toggle for creatinine and weight.
Inputs
Worked example
Patient
Cockcroft-Gault is least reliable when kidney function is changing fast, or in very old, very thin, or very heavy people, or after an amputation. It uses steady creatinine, so a single value during a rapid change misleads.
Kidney function scale
Model: Cockcroft–Gault — assumes steady serum creatinine in an adult with stable kidney function; it estimates, not measures, clearance.
| Band | CrCl range (mL/min) |
|---|
Creatinine clearance
— mL/min
Creatinine clearance (CrCl), an estimate of how fast the kidneys clear creatinine.
Checked against three hand-worked examples (see the page source comments).
Results are rounded to 1 decimal place.
Enter age, weight and creatinine, then tap Show kidney function and dose.
| Value | Result | Unit |
|---|---|---|
| Creatinine clearance (CrCl) | — | mL/min |
| Kidney function band | — | — |
| Weight used | — | kg |
| Creatinine used | — | mg/dL |
| CrCl per 1.73 m² (BSA, Mosteller) | — | mL/min/1.73 m² |
For learning only. Not for patient care decisions. Always check with a qualified professional and the product label.
How it works
Creatinine is made by muscle at a fairly steady rate and cleared almost only by the kidneys, so how fast it leaves the blood says how well the kidneys filter. Cockcroft and Gault turned that into a bedside formula in 1976: take 140 minus the age, multiply by the weight in kilograms, and divide by 72 times the serum creatinine in mg/dL. Women get a 0.85 multiplier because they usually have less muscle, so less creatinine is made. A 60-year-old man of 70 kg with a creatinine of 1.0 mg/dL works out at (80 × 70) / 72 = 77.8 mL/min; the same woman gives 66.1 mL/min.
Units matter more than the arithmetic. Creatinine reported as 88.4 µmol/L is exactly 1.0 mg/dL, so it gives the same 77.8 mL/min for that man, and a weight in pounds must be divided by 2.2046 before it goes in. Which weight to use matters too: in a heavier person the formula can overestimate, because fat makes little creatinine. Ideal body weight comes from height, 50 kg plus 2.3 kg per inch over five feet for a man, 45.5 kg for a woman, and the adjusted weight sits 40 percent of the way from ideal toward actual.
The number is a band, not a verdict: 90 and above is normal, 60 to 89 mildly reduced, 30 to 59 moderately reduced, 15 to 29 severely reduced, and below 15 is kidney failure range. It is an estimate for learning, built for steady creatinine in adults, and it says nothing about which dose any real patient should get.