What is the Cockcroft-Gault formula?

The Cockcroft-Gault equation (1976) estimates creatinine clearance (CrCl) in mL/min using age, sex, actual body weight, and serum creatinine: CrCl = [(140 − age) × weight (kg)] ÷ [72 × serum creatinine (mg/dL)], multiplied by 0.85 for females. It was developed primarily for medication dosing—not for diagnosing chronic kidney disease.

How is creatinine clearance different from eGFR?

Creatinine clearance (CrCl) estimates how much blood the kidneys filter per minute based on creatinine production and excretion. eGFR (estimated glomerular filtration rate) is normalized to body surface area (mL/min/1.73 m²) and uses equations like CKD-EPI for CKD staging. CrCl and eGFR often differ, especially in obese or very muscular people—use eGFR for disease staging and CrCl (Cockcroft-Gault) for many drug dose adjustments.

What creatinine clearance is considered normal?

For adults, CrCl ≥ 90 mL/min is generally considered normal. Mild reduction is often 60–89, moderate 30–59, severe 15–29, and below 15 suggests kidney failure range. Older adults naturally have lower values; interpret results in clinical context rather than as a standalone diagnosis.

Why does the calculator ask for body weight?

Creatinine production correlates with muscle mass, which relates to body weight. Cockcroft-Gault requires actual body weight in kilograms. In obesity, some institutions use adjusted body weight (IBW + 0.4 × [actual − IBW]) because the formula may overestimate clearance—discuss with your pharmacist if you are significantly above ideal weight.

Should I use mg/dL or μmol/L for creatinine?

Enter the unit printed on your laboratory report. mg/dL is common in the United States; μmol/L is common in Europe, Canada, and Australia. Our calculator converts μmol/L to mg/dL internally (÷ 88.42) before applying the Cockcroft-Gault formula.

Which medications are affected by reduced creatinine clearance?

Many drugs are partially or fully cleared by the kidneys: metformin, gabapentin, certain antibiotics (e.g., nitrofurantoin, fluoroquinolones), antivirals, lithium, some opioids, and cardiovascular agents. Dose adjustments often begin when CrCl falls below 50–60 mL/min, but thresholds vary by drug—always check prescribing information or consult a pharmacist.

How accurate is the Cockcroft-Gault calculator?

Cockcroft-Gault is widely used in clinical practice but has limitations: it assumes stable creatinine, may overestimate clearance in obesity, underestimate in malnutrition or amputation, and does not account for race, diet, or muscle mass extremes. It is an estimate—confirm important dosing decisions with measured clearance, eGFR, or specialist guidance.

Can I use this calculator for children?

No. Cockcroft-Gault is validated for adults (typically age 18+). Pediatric kidney function requires age-specific formulas and specialist interpretation. This tool is limited to ages 18–100.

Does creatinine clearance change with age?

Yes. The formula includes age because kidney function typically declines over time. A CrCl of 70 mL/min in a 75-year-old may be less concerning than the same value in a 35-year-old, but medication review is still important at lower clearances regardless of age.

When should I see a doctor about my results?

Seek medical advice if your clearance is below 60 mL/min, if creatinine is rising on repeat labs, or if you have symptoms (swelling, fatigue, reduced urine output, nausea). Do not start, stop, or change medications based solely on an online calculator.

How does this relate to the Kidney Function (eGFR) calculator?

Our eGFR calculator uses CKD-EPI 2021 for CKD staging and kidney health assessment. This CrCl calculator uses Cockcroft-Gault for clearance estimation—especially relevant when adjusting medication doses. Use both tools together for a fuller picture, but follow your clinician's preferred metric for care decisions.

Can dehydration or exercise affect creatinine and CrCl?

Yes. Dehydration, high protein intake, intense exercise, and certain supplements can temporarily raise serum creatinine, which lowers estimated clearance. Repeat testing when well hydrated and at baseline activity if results are unexpected.

Creatinine Clearance (Cockcroft-Gault) Calculator

Estimate creatinine clearance (CrCl) using the Cockcroft-Gault formula with age, sex, height, body weight, and serum creatinine. Adjusted body weight is applied automatically when BMI ≥ 30.

Enter your details — results appear below after you calculate.

Basic information

Age (years)

Sex

Body measurements

Measurement units

Height (cm)

Actual body weight (kg)

If BMI ≥ 30, adjusted body weight is used automatically for CrCl (common obesity dosing approach)

Laboratory values

Creatinine units

Serum creatinine (mg/dL)

Normal range: 0.7–1.2 mg/dL

How this creatinine clearance (Cockcroft-Gault) calculator works

This tool applies the Cockcroft-Gault equation (1976) to estimate creatinine clearance (CrCl) in mL/min: [(140 − age) × weight (kg)] ÷ [72 × serum creatinine (mg/dL)], multiplied by 0.85 for females.

CrCl is primarily used for medication dosing adjustments, not CKD staging (use our eGFR calculator for that). Enter height, actual body weight, age, sex, and serum creatinine in mg/dL or μmol/L.

When BMI ≥ 30, we apply adjusted body weight (Devine IBW + 0.4 × [actual − IBW])—a common approach for obese patients because Cockcroft-Gault may otherwise overestimate clearance.

Results include clearance category, dosing context, health score, and recommendations. Scroll below for detailed articles and FAQs.

Creatinine Clearance (Cockcroft-Gault) Calculator – Estimate Kidney Clearance for Medication Dosing

Creatinine clearance (CrCl) estimates how efficiently your kidneys filter waste from the blood. The Cockcroft-Gault equation (Cockcroft & Gault, Nephron 1976) is one of the most widely used formulas in clinical practice—especially for adjusting medication doses in adults. Unlike eGFR (which is normalized to body surface area for CKD staging), CrCl reflects absolute clearance in mL/min and incorporates actual body weight. Our calculator applies the standard Cockcroft-Gault formula with mg/dL or μmol/L creatinine units, kg or lb weight, sex adjustment, clearance categories, and practical dosing guidance.

What is Creatinine Clearance?

Serum creatinine is a waste product from muscle metabolism that healthy kidneys filter and excrete. When kidney function declines, creatinine accumulates in the blood. Creatinine clearance estimates the volume of blood (in milliliters per minute) that is effectively cleared of creatinine—serving as a proxy for overall kidney filtration capacity.

1Key Inputs for Cockcroft-Gault Calculation

Required Values

Age (years), typically 18–100 for this formula
Sex (male or female)—0.85 multiplier for females
Actual body weight (kg or lb, converted internally)
Serum creatinine (mg/dL or μmol/L from lab report)

Clinical Context

Stable creatinine (not acute kidney injury)
Medications cleared renally or with narrow index
Diabetes, hypertension, or known CKD
Obesity (may need adjusted body weight per protocol)

2How Creatinine Clearance Is Calculated

Cockcroft-Gault formula

CrCl (mL/min) = [(140 − age) × weight (kg)] ÷ [72 × serum creatinine (mg/dL)]

Multiply result by 0.85 if female

When creatinine is reported in μmol/L, we convert to mg/dL (÷ 88.42) before calculation. Weight in pounds is converted to kilograms (× 0.453592). The result is rounded to one decimal place.

CrCl vs eGFR

eGFR (CKD-EPI) expresses filtration rate per 1.73 m² body surface area and is preferred for CKD staging. Cockcroft-Gault CrCl uses actual weight and remains common in drug prescribing references. Values often differ—especially in obesity, low muscle mass, or advanced age. Use our Kidney Function (eGFR) Calculator for staging and this tool for clearance-based dosing context.

Creatinine Clearance Reference Ranges

Category	CrCl (mL/min)	Typical clinical significance
Normal	≥ 90	Most drugs need no renal adjustment
Mildly reduced	60–89	Monitor; some drugs need review below ~60
Moderately reduced	30–59	Frequent dose adjustments; nephrology often involved
Severely reduced	15–29	High toxicity risk; many contraindications or major reductions
Kidney failure range	< 15	Dialysis-range clearance; specialist dosing required

These bands are educational estimates for adults. Individual drug labels may use different CrCl cutoffs (e.g., 50, 30, or 10 mL/min). Always verify against current prescribing information.

How to Use This Calculator

Gather recent lab work – Obtain serum creatinine from a venous blood draw, ideally when you are well hydrated and not acutely ill.
Enter demographics – Age and sex as used in the original Cockcroft-Gault validation (male/female).
Enter actual body weight – Use your current weight in kg or lb. If you are significantly above ideal weight, ask your pharmacist whether adjusted body weight applies.
Select creatinine units – Match your lab report (mg/dL or μmol/L).
Review results – Note CrCl in mL/min, clearance category, dosing context, and recommendations. Share with your prescriber or pharmacist before changing any medication.

Limitations & Important Considerations

1. Not for CKD diagnosis alone

CKD staging uses eGFR and albuminuria, not CrCl alone. Use our eGFR calculator for disease classification and this tool primarily for clearance-based medication context.

2. Obesity and low muscle mass

Cockcroft-Gault may overestimate clearance in obesity and underestimate in malnutrition, amputation, or sarcopenia. Adjusted body weight formulas exist for obese patients.

3. Acute kidney injury

Do not use a single creatinine during acute illness, dehydration, or contrast exposure for long-term dosing decisions. Repeat when creatinine stabilizes.

4. Not a substitute for medical advice

Never start, stop, or change prescription medications based solely on an online calculator. Confirm all dosing with a qualified clinician or pharmacist.

The Science Behind Cockcroft-Gault

Cockcroft and Gault derived their equation from creatinine clearance measurements in 249 patients, correlating age, weight, sex, and serum creatinine with measured clearance. Despite newer eGFR equations, many drug labels and institutional protocols still reference Cockcroft-Gault CrCl for dose adjustment—particularly for antibiotics, antidiabetic agents, and cardiovascular drugs.

Drugs Often Adjusted by CrCl

Metformin, SGLT2 inhibitors (context-dependent)
Gabapentin, pregabalin, lithium
Many antibiotics (nitrofurantoin, fluoroquinolones)
Direct oral anticoagulants (dabigatran, etc.)

When to Recheck Creatinine

After starting nephrotoxic drugs (ACEi, NSAIDs, etc.)
When symptoms suggest declining kidney function
Annually if diabetes, hypertension, or CKD
Before major surgery or contrast procedures

Frequently Asked Questions (FAQs)

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Creatinine Clearance (Cockcroft-Gault) Calculator

Basic information

Body measurements

Laboratory values

How this creatinine clearance (Cockcroft-Gault) calculator works

Creatinine Clearance (Cockcroft-Gault) Calculator – Estimate Kidney Clearance for Medication Dosing

What is Creatinine Clearance?

1Key Inputs for Cockcroft-Gault Calculation

Required Values

Clinical Context

2How Creatinine Clearance Is Calculated

Cockcroft-Gault formula

CrCl vs eGFR

Creatinine Clearance Reference Ranges

How to Use This Calculator

Limitations & Important Considerations

1. Not for CKD diagnosis alone

2. Obesity and low muscle mass

3. Acute kidney injury

4. Not a substitute for medical advice

The Science Behind Cockcroft-Gault

Drugs Often Adjusted by CrCl

When to Recheck Creatinine

Frequently Asked Questions (FAQs)

What is the Cockcroft-Gault formula?

How is creatinine clearance different from eGFR?

What creatinine clearance is considered normal?

Why does the calculator ask for body weight?

Should I use mg/dL or μmol/L for creatinine?

Which medications are affected by reduced creatinine clearance?

How accurate is the Cockcroft-Gault calculator?

Can I use this calculator for children?

Does creatinine clearance change with age?

When should I see a doctor about my results?

How does this relate to the Kidney Function (eGFR) calculator?

Can dehydration or exercise affect creatinine and CrCl?

Related Calculators

Kidney Function (eGFR) Calculator

Corrected Calcium Calculator

Anion Gap Calculator

BUN/Creatinine Ratio Calculator

HbA1c ↔ Average Blood Glucose Calculator

Type 2 Diabetes Risk Assessment Calculator

Sodium Intake Calculator

Blood Pressure Interpreter & Risk Calculator

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