What is the Cockcroft-Gault formula?

Creatinine clearance equals (140 minus age) times weight in kg, divided by 72 times serum creatinine in mg/dL. The result is multiplied by 0.85 for females. It estimates kidney function in mL/min and is the classic equation for renal drug dosing.

Why is Cockcroft-Gault still used over eGFR?

Many drug labels and dose-adjustment tables were validated against Cockcroft-Gault creatinine clearance, so pharmacists often use it for prescribing decisions even though eGFR equations are preferred for staging chronic kidney disease.

Should I use actual, ideal, or adjusted body weight?

The original equation uses actual body weight, but for obese patients many references recommend ideal or adjusted body weight to avoid overestimating clearance. This tool uses the weight you enter, so apply your institution's policy when choosing it.

How do I convert umol/L creatinine?

Divide serum creatinine in micromol per litre by 88.42 to get mg/dL. The tool does this for you when you select SI units, so you can enter the value your lab reports directly.

Is this medical advice?

No. It is an educational calculator. Renal dosing decisions must be confirmed by a qualified clinician using current prescribing information and the full clinical picture. No data leaves your browser.

Creatinine Clearance (Cockcroft-Gault)

The Cockcroft-Gault equation estimates creatinine clearance, a measure of kidney function, from routine bedside values. It remains the reference method for adjusting drug doses in renal impairment because so many drug labels were written against it.

How it works

The equation, in conventional US units, is:

CrCl (mL/min) = ((140 - age) * weight_kg) / (72 * SCr_mg_dL)
             *  0.85 if the patient is female

If serum creatinine is reported in µmol/L (SI units), it is first converted to mg/dL by dividing by 88.42. The tool then maps the result to a function band so you can see at a glance whether clearance is normal, mildly, moderately, or severely reduced.

Example

A 65-year-old man weighing 80 kg with a serum creatinine of 1.1 mg/dL: CrCl = ((140 − 65) × 80) ÷ (72 × 1.1) = 6000 ÷ 79.2 ≈ 75.8 mL/min, a mild reduction.

Notes

Cockcroft-Gault uses actual body weight by default; for obese or very underweight patients, ideal or adjusted body weight is often substituted to avoid over- or under-estimating clearance. Treat the result as an estimate to be confirmed clinically, not a diagnosis.