Rex says
Same equations the textbooks use — just way less awkward. Pop in your stats and I'll tell you what the number actually means for you.
Try a scenario
Click to load — tweak from there.Inputs
Result
Creatinine clearance
75.8
Function category
Mildly reduced
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter age (years).
- 2Enter weight (kg).
- 3Enter serum creatinine (mg/dL).
- 4Enter sex.
- 5Read your creatinine clearance on the right — it updates as you type.
- 6Hit Share to keep the scenario or send it to someone.
About this calculator
Cockcroft-Gault estimates creatinine clearance from age, weight, sex, and serum creatinine, and it remains the standard equation referenced in most drug package inserts for renal dose adjustment, especially for agents like vancomycin, DOACs, and many antibiotics. Unlike eGFR equations built for CKD staging, Cockcroft-Gault was derived and validated specifically for dosing decisions, which is why pharmacists and prescribers still reach for it even though eGFR (CKD-EPI) is preferred for diagnosing kidney disease. The formula uses actual body weight by default, but many clinicians substitute ideal or adjusted body weight in obese patients to avoid overestimating clearance, since creatinine generation does not scale with fat mass the way it does with lean tissue. Results are unreliable in unstable renal function, extremes of muscle mass, amputees, or during acute kidney injury, where creatinine has not reached steady state. Always check the specific drug label for which weight input it expects. This tool is for education and workflow support only — not medical advice. Always verify results with a clinician and use clinical judgment alongside your institution's protocols.
Worked example
Using the values the calculator loads with:
Inputs
- Age: 65 years
- Weight: 80 kg
- Serum creatinine: 1.1 mg/dL
- Sex: Male
Results
- Creatinine clearance: 75.8
- Function category: Mildly reduced
What each field means
Inputs
- Age (years)
- The age used in the calculation, measured in years. Starts at 65 years so you have a working example on load. Accepted range: 18–110 years.
- Weight (kg)
- The weight used in the calculation, measured in kg. Starts at 80 kg so you have a working example on load. Accepted range: 20–250 kg.
- Serum creatinine (mg/dL)
- The serum creatinine used in the calculation, measured in mg/dL. Starts at 1.1 mg/dL so you have a working example on load. Accepted range: 0.2–15 mg/dL.
- Sex
- Pick the option that matches your situation — the maths changes per option. Choices: Male, Female.
Results
- Creatinine clearance
- Returned as a decimal number and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Function category
- Returned as a plain value. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
Should I use actual or ideal body weight?
Use actual body weight if the patient is at or under ideal body weight. If actual weight exceeds ideal weight by more than about 20-30%, most pharmacists switch to adjusted body weight (ideal + 0.4 × excess weight) because fat contributes little to creatinine production and using actual weight would overestimate clearance and risk overdosing.
Why not just use eGFR for dosing?
eGFR equations like CKD-EPI are normalized to a standard 1.73 m² body surface area, which is useful for staging chronic kidney disease across a population but can misrepresent an individual patient's actual clearance, particularly at extremes of body size. Cockcroft-Gault reports an un-normalized value tied to the patient's real body, which is what drug clearance actually depends on.
How reliable is this in acute kidney injury?
Not very. The equation assumes creatinine is at steady state, which is not true during rapidly changing renal function. In AKI, serum creatinine lags the real-time GFR, so calculated clearance can look falsely reassuring on the way down and falsely low on the way up. Use direct measurement or clinical judgment instead.
Does muscle mass affect the result?
Yes, significantly. Serum creatinine comes from muscle breakdown, so a frail, low-muscle-mass elderly patient can have a 'normal' creatinine despite meaningfully reduced kidney function, while a bodybuilder can have an elevated creatinine with normal kidneys. Interpret extreme muscle mass cases cautiously.
Accuracy and limitations
- Population formulas describe averages; individual bodies vary, especially at the extremes of height, age, or muscle mass.
- Results do not account for medical conditions, medication, or pregnancy.
- Use this as a directional reference, not a diagnosis — talk to a clinician before acting on it.
Related tools
Ideal Body Weight Calculator (Devine Formula)
Devine formula IBW used for drug dosing and ventilator settings.
Adjusted Body Weight Calculator
Dosing weight for obese patients that blends actual and ideal weight.
Fractional Excretion of Sodium (FeNa) Calculator
Distinguish prerenal from intrinsic acute kidney injury.
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Creatinine Clearance Calculator (Cockcroft-Gault). Retrieved from https://www.revenuelab.fyi/toolbox/creatinine-clearance-cockcroft-gault
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/creatinine-clearance-cockcroft-gault" target="_blank" rel="noopener">Creatinine Clearance Calculator (Cockcroft-Gault) — RevenueLab</a> (2026).</p>
Source: [Creatinine Clearance Calculator (Cockcroft-Gault) — RevenueLab](https://www.revenuelab.fyi/toolbox/creatinine-clearance-cockcroft-gault) (2026).