This calculator estimates creatinine clearance with the Cockcroft–Gault equation, an older kidney-function estimate still referenced in some medicine labels and dosing decisions. It reports one result using entered body weight and a second result using an adjusted body weight derived from height. Results are expressed in mL/min and are not normalized to a body surface area of 1.73 m².
This is educational information, not a diagnosis or dosing instruction. A clinician or pharmacist should decide which kidney estimate and which weight are appropriate for a particular medicine and patient. The estimate can be unreliable when serum creatinine is changing rapidly or body composition differs markedly from the population used to develop the equation.
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How to Use This Calculator
Select the equation’s male or female coefficient and enter age in completed years.
Enter body weight in kilograms or pounds. Pounds are converted to kilograms.
Enter serum creatinine in mg/dL or µmol/L. The tool converts µmol/L to mg/dL by dividing by 88.4.
Enter height in inches or centimetres. Height is used to calculate ideal body weight, then adjusted body weight.
Select Calculate to see Cockcroft–Gault with entered weight, Cockcroft–Gault with adjusted weight, and the span between them.
The page always displays both weight approaches. That does not mean adjusted body weight is suitable in every case; weight selection should follow the relevant clinical or medication guidance.
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Formula Used
Male-coefficient CrCl = [(140 − age) × weight in kg] ÷ [72 × serum creatinine in mg/dL].
For the female coefficient, multiply that result by 0.85.
Ideal body weight used here = 50 + 2.3 × (inches over 60) for male, or 45.5 + 2.3 × (inches over 60) for female. Adjusted weight = IBW + 0.4 × (actual weight − IBW).
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Variables Explained
Entry or result
Meaning
Important detail
Age
Age in years
The numerator falls as age rises; the equation was developed for adults.
Weight
Body weight used by Cockcroft–Gault
The page reports actual-weight and adjusted-weight versions.
Serum creatinine
Laboratory creatinine concentration
Enter the value with its matching unit; µmol/L and mg/dL are not numerically interchangeable.
Height
Standing height
Used only to derive ideal and adjusted body weight.
CrCl
Estimated creatinine clearance
Reported in mL/min, without body-surface-area indexing.
Range
Lower and higher of the two displayed estimates
It is not a confidence interval or a normal reference range.
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Worked Example
For a 60-year-old man who weighs 100 kg, is 70 inches tall, and has serum creatinine of 1.0 mg/dL, the entered-weight estimate is (140 − 60) × 100 ÷ (72 × 1) = 111.1 mL/min.
The page’s ideal weight is 50 + 2.3 × (70 − 60) = 73.0 kg. Adjusted weight is 73 + 0.4 × (100 − 73) = 83.8 kg. Repeating Cockcroft–Gault with 83.8 kg gives 93.1 mL/min. The displayed range is therefore 93.1 to 111.1 mL/min. This spread only shows the effect of the two weight choices; it does not measure every source of clinical uncertainty.
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Why Use This Calculator?
A larger estimate generally indicates greater calculated clearance under this equation, but one number should not be interpreted in isolation. Creatinine production, muscle mass, diet, laboratory method, hydration, age, and acute illness can affect the relationship between serum creatinine and kidney function. Cockcroft–Gault CrCl is also different from the eGFR commonly printed on laboratory reports.
For medication review, use the method named in current prescribing information or local protocol and have a qualified professional verify the inputs. The National Kidney Foundation notes that newer eGFR equations are preferred for assessing kidney function, while Cockcroft–Gault persists in some drug-dosing contexts.
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Common Mistakes
Entering a µmol/L laboratory value while leaving mg/dL selected. For example, 88.4 µmol/L is approximately 1.0 mg/dL.
Assuming the adjusted-weight result is automatically the correct one. Weight choice depends on context.
Treating the displayed span as a laboratory normal range or statistical confidence interval.
Substituting this unindexed mL/min estimate directly for eGFR in mL/min/1.73 m².
Using a single creatinine-based estimate when kidney function is changing quickly.
Changing a medicine dose without clinician or pharmacist review.
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Frequently Asked Questions
Is creatinine clearance the same as eGFR?
No. This page reports Cockcroft–Gault in mL/min. Laboratory eGFR commonly uses a different equation and is usually indexed to 1.73 m² of body surface area. They can give different values and are not automatically interchangeable.
Which body weight should I use?
There is no single choice for every patient and medicine. This page shows entered weight and its own adjusted-weight calculation so the assumption is visible. A clinician or pharmacist should follow the relevant label or protocol.
Can the result be used during acute kidney injury?
Use particular caution. Creatinine-based steady-state equations can lag behind rapidly changing kidney function, so the estimate may not represent current clearance. Clinical assessment and repeat measurements may be needed.
Why does the equation use a female multiplier?
The original equation used 0.85 as a sex-based adjustment intended to reflect average creatinine generation in its source population. It is a historical population coefficient and does not measure an individual’s muscle mass.
Does the displayed range show whether kidney function is normal?
No. It is simply the minimum and maximum of the actual-weight and adjusted-weight calculations. Interpretation depends on the clinical question, the patient, trends over time, and the method required for a medicine or guideline.
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