🩺 Creatinine Clearance Calculator (Cockcroft-Gault)
By Shihab Mia · Updated 2026-07-04
This creatinine clearance calculator gives a general estimate for education only and is not professional medical advice, a diagnosis, or a drug dosing instruction. The Cockcroft-Gault estimate can be inaccurate in acute kidney injury, pregnancy, and at the extremes of body size or muscle mass. Always confirm kidney function and any medication decisions with a qualified clinician or pharmacist.
Enter age, sex, body weight and your serum creatinine value. Use the unit toggles to match your lab report and your local units.
A creatinine clearance calculator estimates how quickly your kidneys filter creatinine, a muscle waste product, out of your blood. Enter your age, sex, body weight and serum creatinine, and this tool applies the Cockcroft-Gault equation to return an estimated creatinine clearance (CrCl) in mL/min in seconds. Roughly 90 mL/min or above is considered normal, and lower numbers suggest reduced kidney filtering. It is the same method clinicians and pharmacists often use as a starting point when they need a quick read on kidney function or a renal drug dose.
What is the Creatinine Clearance Calculator?
This creatinine clearance calculator uses the Cockcroft-Gault equation, published in 1976 and still one of the most widely used kidney function formulas in the world. The core formula is CrCl = ((140 minus age) times weight in kg) divided by (72 times serum creatinine in mg/dL), and the result is then multiplied by 0.85 for women because, on average, women carry less muscle mass and therefore produce less creatinine. Because creatinine sits in the denominator, a higher serum creatinine pushes the estimated clearance down: when the kidneys clear creatinine slowly, it builds up in the blood.
Units are the single biggest source of a wildly wrong result, so this tool lets you toggle them. Serum creatinine is reported in mg/dL in the United States and in micromol/L across most of the rest of the world. To convert micromol/L to mg/dL you divide by 88.4, which the calculator does automatically. Weight can be entered in kilograms or pounds, and the tool converts pounds to kilograms before running the equation. If a creatinine clearance result looks off by a factor of roughly 88, a swapped creatinine unit is almost always the reason.
Which body weight to enter is the second thing that trips people up. The original Cockcroft-Gault equation was validated with actual body weight, and that is the default this calculator expects. In clinical practice, however, many pharmacists adjust: for underweight patients they often use actual body weight, for normal-weight patients some use ideal body weight, and for patients whose actual weight exceeds about 130 percent of their ideal body weight they commonly use an adjusted body weight, calculated as ideal weight plus 0.4 times the difference between actual and ideal weight. Ideal body weight itself comes from the Devine formula (50 kg for men or 45.5 kg for women, plus 2.3 kg for every inch over 5 feet). These choices can change a renal dose, so a clinician should make the final call.
Creatinine clearance is closely related to, but not identical to, estimated glomerular filtration rate (eGFR). Both describe kidney filtering, but they use different equations and are not interchangeable. Cockcroft-Gault produces a raw clearance in mL/min and was the historical standard for adjusting medication doses, which is why many drug labels and package inserts still reference it directly. Modern eGFR equations such as CKD-EPI are now preferred for staging chronic kidney disease and are usually normalised to a body surface area of 1.73 square metres, expressed as mL/min/1.73m2. For drug dosing specifically, many pharmacists still calculate a Cockcroft-Gault creatinine clearance rather than relying on eGFR.
The creatinine clearance formula has real limits you should respect. It assumes a stable, steady serum creatinine, so it is unreliable when kidney function is changing quickly, such as during acute kidney injury or rapid recovery, because creatinine lags behind the true filtration rate. It can mislead at the extremes of body size, in pregnancy, in amputees or people with unusually high or low muscle mass, and in frail older adults whose low muscle mass makes creatinine look deceptively good and can hide real impairment. For very low creatinine values in elderly or cachectic patients, some clinicians round the serum creatinine up toward 1.0 mg/dL to avoid overestimating clearance, though this practice is debated and not firmly evidence based.
Treat the number from this creatinine clearance calculator as a screening estimate that starts a conversation, not as a final clinical figure. It is genuinely useful for spotting a trend over time, for understanding how age, weight and serum creatinine each move the result, and for sanity checking a renal dose. But any decision that affects treatment, from staging chronic kidney disease to adjusting a medication, belongs with a doctor or pharmacist who can see your full clinical picture.
When to use it
- Getting a fast, ballpark read on kidney function from a recent blood test before a doctor or pharmacy visit.
- Checking the Cockcroft-Gault creatinine clearance a pharmacist might use when a medication needs renal dose adjustment.
- Comparing two results over time to see whether an estimated creatinine clearance is trending up or down.
- Learning how age, sex, weight and serum creatinine each move the estimated clearance, for study or exam revision.
- Understanding why a CrCl number can differ from an eGFR reported on the same lab panel.
- Sanity checking a dose reduction after starting a drug that is cleared mainly by the kidneys.
How to use the Creatinine Clearance Calculator
- Enter your age in years and select your sex, since the equation lowers the result by 15 percent for women.
- Enter your body weight and choose kilograms or pounds with the unit toggle; use actual body weight unless a clinician has told you otherwise.
- Enter your serum creatinine from your lab report and pick mg/dL or micromol/L to match the unit printed on the report.
- Read your estimated creatinine clearance in mL/min and the general kidney function band shown beneath it.
- Recheck the units if the number looks far too high or low, then take the result to a clinician for any real decision.
Formula & method
Worked examples
A 60 year old man weighing 70 kg with a serum creatinine of 1.0 mg/dL.
- 140 minus age = 140 minus 60 = 80
- Multiply by weight: 80 x 70 = 5600
- Divide by (72 x creatinine): 72 x 1.0 = 72, so 5600 / 72 = 77.8
- He is male, so no 0.85 factor is applied
Result: Estimated CrCl is about 78 mL/min, in the mildly reduced band.
A 72 year old woman weighing 132 lb with a serum creatinine of 106 micromol/L.
- Convert weight: 132 / 2.20462 = 59.9 kg
- Convert creatinine: 106 / 88.4 = 1.2 mg/dL
- Apply the formula: ((140 minus 72) x 59.9) / (72 x 1.2) = (68 x 59.9) / 86.4 = 4073 / 86.4 = 47.1
- She is female, so multiply by 0.85: 47.1 x 0.85 = 40.1
Result: Estimated CrCl is about 40 mL/min, in the moderately reduced band.
A 40 year old man weighing 80 kg with a serum creatinine of 0.9 mg/dL.
- 140 minus age = 140 minus 40 = 100
- Multiply by weight: 100 x 80 = 8000
- Divide by (72 x creatinine): 72 x 0.9 = 64.8, so 8000 / 64.8 = 123.5
- He is male, so no 0.85 factor is applied
Result: Estimated CrCl is about 123 mL/min, comfortably in the normal band.
General creatinine clearance bands for context (not a diagnosis)
| Estimated CrCl (mL/min) | General description |
|---|---|
| 90 or above | Normal kidney function |
| 60 to 89 | Mildly reduced |
| 30 to 59 | Moderately reduced |
| 15 to 29 | Severely reduced |
| Under 15 | Kidney failure range |
Which body weight clinicians often use in Cockcroft-Gault
| Body size | Weight often used | Why |
|---|---|---|
| Underweight (actual below ideal) | Actual body weight | Avoids overestimating clearance |
| Normal weight | Actual or ideal body weight | Both give similar, reasonable estimates |
| Obese (actual above about 130% of ideal) | Adjusted body weight | Actual weight can overestimate clearance |
Quick unit conversions used by this calculator
| Convert from | Convert to | Operation |
|---|---|---|
| Serum creatinine micromol/L | mg/dL | Divide by 88.4 |
| Serum creatinine mg/dL | micromol/L | Multiply by 88.4 |
| Weight in pounds | kilograms | Divide by 2.20462 |
| Weight in kilograms | pounds | Multiply by 2.20462 |
Common mistakes to avoid
- Mixing up the creatinine units. A serum creatinine of 88 looks very different depending on the unit. If your lab reports micromol/L but you treat it as mg/dL, the result will be roughly 88 times too low. Always set the toggle to match your report, or divide micromol/L by 88.4 first.
- Forgetting the female factor. The raw Cockcroft-Gault formula is multiplied by 0.85 for women. Leaving this out overestimates clearance by about 15 percent. This calculator applies the factor automatically once you select sex.
- Confusing creatinine clearance with eGFR. CrCl and eGFR both describe kidney filtering but use different equations and are not interchangeable. eGFR from CKD-EPI is preferred for staging chronic kidney disease, while Cockcroft-Gault CrCl is still common for drug dosing. Do not swap one number for the other.
- Using the wrong body weight in obesity. Entering a very high actual body weight for an obese person can overestimate clearance, because fat tissue does not produce much creatinine. For patients well above ideal weight, clinicians often switch to an adjusted body weight, so check before trusting a dose.
- Trusting it during fast changing kidney function. The equation assumes a stable serum creatinine. During acute kidney injury or rapid recovery, creatinine lags behind the real filtration rate, so any single estimate can be misleading and should only be interpreted by a clinician.
- Overtrusting a low creatinine in a frail older adult. Low muscle mass in elderly or cachectic patients can make serum creatinine look deceptively normal and inflate the estimated clearance. Some clinicians round a very low creatinine up toward 1.0 mg/dL to avoid overestimating kidney function.
Glossary
- Creatinine clearance
- An estimate of the volume of blood, in mL per minute, that the kidneys clear of creatinine, used as a marker of kidney function.
- Serum creatinine
- The concentration of creatinine measured in a blood sample; higher values usually mean slower kidney filtering.
- Cockcroft-Gault equation
- A 1976 formula that estimates creatinine clearance from age, weight, sex and serum creatinine.
- eGFR
- Estimated glomerular filtration rate, a related but distinct measure of kidney function from equations such as CKD-EPI, usually reported per 1.73 square metres of body surface area.
- Ideal body weight
- A height based reference weight, commonly from the Devine formula, sometimes used instead of actual weight in the equation.
- Adjusted body weight
- A weight between ideal and actual weight, often used for obese patients as ideal plus 0.4 times the difference from actual weight.
- mg/dL
- Milligrams per deciliter, the creatinine unit common in the United States.
- micromol/L
- Micromoles per liter, the creatinine unit common outside the United States; divide by 88.4 to get mg/dL.
Frequently asked questions
How do I calculate creatinine clearance?
Use the Cockcroft-Gault equation: take (140 minus your age), multiply by your weight in kilograms, then divide by (72 times your serum creatinine in mg/dL). Multiply the result by 0.85 if you are female. This creatinine clearance calculator runs that calculation and handles the unit conversions for you.
What is a normal creatinine clearance?
As a rough guide, an estimated creatinine clearance of 90 mL/min or above is considered normal, 60 to 89 is mildly reduced, 30 to 59 is moderately reduced, 15 to 29 is severely reduced and under 15 is in the kidney failure range. These bands are general context, not a diagnosis.
Is creatinine clearance the same as eGFR?
No. Both estimate kidney function but they use different formulas and are not interchangeable. eGFR from CKD-EPI is usually preferred for staging chronic kidney disease, while Cockcroft-Gault creatinine clearance is still widely used for adjusting medication doses. eGFR is also normalised to body surface area, while Cockcroft-Gault gives a raw mL/min value.
Which weight should I use, actual or ideal body weight?
The original Cockcroft-Gault equation uses actual body weight, which is what this calculator expects by default. In practice, some pharmacists use ideal body weight for normal-weight patients and an adjusted body weight for obese patients whose actual weight is well above ideal, so check with a professional for dosing decisions.
Why is the creatinine clearance result lower for women?
On average women have less muscle mass than men and so produce less creatinine for the same kidney function. The Cockcroft-Gault equation corrects for this by multiplying the result by 0.85 when sex is set to female.
Can I rely on this number for medication dosing?
No. This is an educational estimate. Real dosing decisions depend on the full clinical picture, the specific drug, and sometimes a different body weight or a measured clearance. Always let a doctor or pharmacist make the final call on renal dose adjustment.
How do I convert serum creatinine from micromol/L to mg/dL?
Divide the micromol/L value by 88.4 to get mg/dL. For example, 106 micromol/L divided by 88.4 is about 1.2 mg/dL. This calculator does the conversion automatically when you set the creatinine unit toggle to match your lab report.
Why does my creatinine clearance drop as I get older?
The equation subtracts your age from 140, so the estimate falls as age rises even if your serum creatinine is unchanged. This reflects the natural, gradual decline in kidney filtering that occurs with age in most people, though the exact number is only an estimate.
What causes a falsely high or low creatinine clearance estimate?
Unusually high muscle mass, dehydration, or a recent high-protein or creatine intake can shift serum creatinine and distort the estimate, while very low muscle mass in frail or elderly people can make clearance look better than it is. Rapidly changing kidney function, pregnancy, and amputation also reduce accuracy.
Is a higher creatinine clearance always better?
Not necessarily. A CrCl above roughly 90 mL/min is normal, but a very high value can sometimes reflect low muscle mass or a measurement quirk rather than excellent kidney health. What matters most is whether the number is stable and appropriate for your age, size and clinical situation, which a clinician can judge.
Sources
- Prediction of creatinine clearance from serum creatinine , Cockcroft and Gault, Nephron (1976)
- Estimating Glomerular Filtration Rate , U.S. National Institute of Diabetes and Digestive and Kidney Diseases (2024)
- Creatinine Clearance Calculator , ClinCalc (2025)