Creatinine clearance from the Cockcroft-Gault equation is still the number many drug labels use for renal dose bands, which is why pharmacists ask for it and why nurses meet it on vancomycin, gentamicin, enoxaparin and direct oral anticoagulant orders. This calculator gives CrCl from actual body weight and, if you add height, from ideal and adjusted body weight too, because in obese patients the choice of weight changes the answer more than anything else.
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CrCl (mL/min) = (140 − age) × weight (kg) ÷ (72 × serum creatinine in mg/dL), multiplied by 0.85 for females. A 55-year-old man weighing 70 kg with a creatinine of 1.0 mg/dL: 85 × 70 ÷ 72 = 82.6 mL/min.
Cockcroft and Gault built the equation in 1976 from 249 men. The 0.85 for women was their own suggested adjustment for lower average muscle mass, not something they measured. The result is not scaled to body surface area, which is why it comes out in plain mL/min and why drug labels written around it use it directly.
If your lab reports creatinine in µmol/L, divide by 88.4 to get mg/dL before using the formula. A creatinine of 106 µmol/L is 1.2 mg/dL. Mixing the units is the most common way to get a wildly wrong result, and the calculator converts it for you.
The original paper used actual body weight. In obesity that overestimates clearance, because fat adds weight without adding much creatinine production. Practice varies, but a common approach is:
| Patient | Weight usually used |
|---|---|
| Actual weight at or below ideal body weight | Actual body weight |
| Actual weight up to about 120% of ideal | Ideal or actual body weight (protocols differ) |
| Actual weight above about 120% of ideal (obese) | Adjusted body weight = IBW + 0.4 × (actual − IBW) |
Here is how much it matters, for a 70-year-old man, 170 cm tall, weighing 130 kg, with a creatinine of 1.6 mg/dL:
| Weight used | Weight | CrCl |
|---|---|---|
| Actual body weight | 130 kg | 79.0 mL/min |
| Ideal body weight (Devine) | 65.9 kg | 40.1 mL/min |
| Adjusted body weight (IBW + 0.4 × excess) | 91.6 kg | 55.6 mL/min |
Same patient, three answers. Actual weight puts him in the mild band; ideal and adjusted weight both put him in the moderate band, where many renally cleared drugs change dose. That is why the weight choice belongs to the pharmacy protocol, not to whoever happens to be holding the calculator. Ideal body weight here uses the Devine formula; the ideal body weight calculator shows the working.
| CrCl (mL/min) | Band | What it usually means for dosing |
|---|---|---|
| 90 or higher | Normal | Standard dosing |
| 60–89 | Mild impairment | Usually standard dosing; check drugs with a narrow margin |
| 30–59 | Moderate impairment | Many renally cleared drugs need a lower dose or longer interval |
| 15–29 | Severe impairment | Significant adjustment; some drugs are avoided |
| below 15 | Kidney failure | Dosing depends on dialysis; pharmacy and nephrology input |
These bands follow the categories used in FDA renal impairment guidance and most drug labels, but each drug has its own cut-offs. Enoxaparin changes at 30 mL/min; some direct oral anticoagulants change at 50 or 15. Always take the cut-off from the drug reference.
| Patient | Serum creatinine | CrCl | Band |
|---|---|---|---|
| 40 y, male, 80 kg | 0.9 mg/dL | 123.5 mL/min | Normal |
| 55 y, male, 70 kg | 1.0 mg/dL | 82.6 mL/min | Mild impairment |
| 70 y, female, 60 kg | 1.2 mg/dL | 41.3 mL/min | Moderate impairment |
| 65 y, male, 75 kg | 2.0 mg/dL | 39.1 mL/min | Moderate impairment |
| 80 y, female, 55 kg | 1.5 mg/dL | 26.0 mL/min | Severe impairment |
The 80-year-old woman has a creatinine that would not raise many eyebrows on a lab sheet, yet her clearance sits in the severe band. Age and low body weight do most of the work. That pattern is common on elderly care wards and is exactly where renally cleared drugs cause harm.
Cockcroft-Gault assumes creatinine is stable. In acute kidney injury it is not, and the estimate runs high until creatinine catches up. Very low muscle mass, in frail older adults, people with paralysis or amputations, or after a long ICU stay, gives a low creatinine and an overestimated clearance. Some units round a low creatinine up to 1.0 mg/dL in older patients to compensate; others consider that inaccurate. It is a local policy question. Modern IDMS-standardised creatinine assays also read slightly lower than the methods used in 1976, which nudges results up. When accuracy really matters, a measured 24-hour urine creatinine clearance or a cystatin C based estimate is more reliable.
CrCl in mL/min = (140 − age) × weight in kg ÷ (72 × serum creatinine in mg/dL), multiplied by 0.85 for females. With creatinine in µmol/L, divide it by 88.4 first.
Roughly 90 to 120 mL/min in healthy young adults, a little higher in men than women. It falls with age. Drug labels commonly treat 60–89 as mild, 30–59 as moderate and 15–29 as severe impairment, with below 15 as kidney failure.
Actual body weight for most patients, and actual weight when it is below ideal. When actual weight is more than about 120% of ideal, many protocols use adjusted body weight (IBW + 0.4 × the excess) because actual weight overestimates clearance. The local pharmacy protocol decides.
Cockcroft and Gault derived the equation in men and suggested multiplying by 0.85 for women to allow for lower average muscle mass and creatinine production. It is a fixed adjustment, not an individual measurement.
No. CrCl from Cockcroft-Gault is in mL/min and not adjusted for body size. eGFR is reported per 1.73 m² of body surface area. They can differ substantially in small, large or elderly patients, and drug references specify which one their dose bands use.