Creatinine Clearance Calculator
Estimate CrCl with the Cockcroft-Gault equation the way a pharmacist actually does it: the right dosing weight, honest creatinine handling, and the exact drug-label cut-offs your number lands near.
Written by Manzoor Ahmad, Pharm-D
Last updated September 17, 2026
Built on Cockcroft & Gault (Nephron, 1976), staged with the FDA renal impairment guidance (2024), and weight-adjusted per the Wilhelm meta-analysis.
Patient details
Results update as you type. Nothing you enter leaves your browser.
US labs report mg/dL. Pakistan, the UK, Europe, and Australia usually report µmol/L (1 mg/dL = 88.4 µmol/L).
Rounding is a common hospital habit, but most studies find it underestimates kidney function. Use it only if your protocol requires it.
Your result
Enter age, weight, and serum creatinine. Add height so the calculator can choose between actual, ideal, and adjusted body weight.
Where this sits on the kidney function scale
Bands follow the FDA renal function categories. Ticks mark CrCl values that appear most often on drug labels.
Same patient, three body weights
The weight you feed the formula can move CrCl more than a small creatinine change. The highlighted card is the one used above.
Actual weight
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— kg
Ideal weight
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needs height
Adjusted weight
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needs height
Body measurements behind the number
How much creatinine rise would change the category
For this patient’s age, sex, and weight, these are the creatinine levels that would pull CrCl under each common cut-off.
Label cut-offs this CrCl lands in
Educational snapshot of US prescribing information. Indication, formulation, and local labels vary, so confirm the dose with a pharmacist or prescriber.
Show the calculation step by step
Your worked calculation appears here once the result is ready.
What is creatinine clearance?
Creatinine clearance (CrCl) is the volume of blood your kidneys clear of creatinine each minute, reported in mL/min. Clinicians estimate it with the Cockcroft-Gault equation, using age, weight, sex, and serum creatinine, mainly to decide whether a medicine needs a lower dose. A healthy adult usually sits roughly between 90 and 140 mL/min.
Creatinine is a waste product from normal muscle turnover. Your muscles release it at a fairly steady rate, and your kidneys filter it out. When filtration slows, creatinine builds up in the blood, so a higher serum creatinine usually means lower clearance. The Cockcroft-Gault equation turns that single blood value into an estimate of how many millilitres of blood are being cleaned per minute, which is the number drug labels are written around.
In nine years of pharmacy practice, the question I field most about kidney function isn’t “what is my eGFR?” It’s “why did my doctor lower the dose of my medicine when my report says my kidneys are fine?” The answer is almost always this calculation. A lab report flags creatinine against a population range, while the dose decision runs through CrCl, and those two can tell very different stories for an 80-year-old, 50 kg woman.
The Cockcroft-Gault formula, explained
CrCl (mL/min) = [(140 − age) × weight in kg] ÷ (72 × serum creatinine in mg/dL)
Multiply the result by 0.85 for females.
With creatinine in µmol/L: CrCl = [(140 − age) × weight × 1.23] ÷ creatinine, using 1.04 instead of 1.23 for females.
Donald Cockcroft and Henry Gault published this equation in 1976 from data on 249 hospitalized men with stable kidney function. Each piece of it has a physical meaning, which is why it has survived fifty years:
- (140 − age) reflects the gradual loss of muscle mass and kidney function with age, so an 80-year-old produces less creatinine than a 30-year-old of the same weight.
- Weight stands in for muscle mass, which drives how much creatinine the body makes. This is also the formula’s weak point in obesity, because fat produces almost no creatinine.
- 72 × serum creatinine converts the blood level into a clearance rate. The higher the creatinine, the lower the result.
- 0.85 for females accounts for lower average muscle mass. The original paper applied this factor as an estimate rather than deriving it from female patients.
One detail people miss: Cockcroft-Gault gives an absolute value in mL/min, not a value indexed to 1.73 m² of body surface area like eGFR. That is exactly why it is useful for dosing. A drug’s clearance depends on the actual kidneys in front of you, not on a standardized body size.
Worked example: how the weight choice changes a dose
Take a 70-year-old man, 175 cm tall, weighing 80 kg, with a stable serum creatinine of 1.4 mg/dL (124 µmol/L). His BMI is 26.1, so he falls in the overweight range and his ideal body weight is about 70.5 kg.
| Weight used | Weight (kg) | Calculation | CrCl (mL/min) |
|---|---|---|---|
| Actual body weight | 80.0 | (70 × 80) ÷ (72 × 1.4) | 55.6 |
| Adjusted body weight | 74.3 | (70 × 74.3) ÷ (72 × 1.4) | 51.6 |
| Ideal body weight | 70.5 | (70 × 70.5) ÷ (72 × 1.4) | 48.9 |
Now suppose he takes rivaroxaban for atrial fibrillation. The US label switches from 20 mg to 15 mg daily at a CrCl of 50 mL/min or below. With actual or adjusted weight he stays on 20 mg. With ideal weight he drops to 15 mg. Same man, same blood test, different dose. This is why the calculator above shows all three weights side by side instead of hiding the choice, and why it uses actual body weight for the anticoagulant checks: the landmark trials behind those labels calculated CrCl with actual weight.
Which body weight should you use?
There is no single rule every hospital follows, but the evidence points in a consistent direction. A 2011 meta-analysis in Pharmacotherapy found that Cockcroft-Gault with an unadjusted creatinine tracked measured clearance most closely, and that in obese patients an adjusted weight with a 0.3 to 0.4 correction factor was reasonable. A transplant-population study reached a similar conclusion, with adjusted weight (0.4) performing best in overweight and obese adults. The calculator’s Auto setting follows the widely used BMI-based approach:
| Patient’s BMI | Weight Auto uses | Why |
|---|---|---|
| Under 18.5 | Actual body weight | Ideal weight would overstate muscle mass and inflate CrCl. |
| 18.5 to 24.9 | Lower of actual or ideal | Keeps the estimate conservative in normal-weight adults. |
| 25 or higher | Adjusted body weight | Counts only 40% of excess weight, since fat produces little creatinine. |
| No height entered | Actual body weight | Ideal and adjusted weight cannot be calculated without height. |
The formulas behind ideal and adjusted weight
Ideal body weight (Devine): 50 kg for men or 45.5 kg for women, plus 2.3 kg for every inch over 5 feet. Adjusted body weight: ideal weight + 0.4 × (actual weight − ideal weight). If you work with very short adults under 5 feet, treat the Devine result cautiously, because the equation was never designed for that height range.
Creatinine clearance ranges and kidney function stages
The FDA’s 2024 renal impairment guidance groups kidney function into the same bands whether you use eGFR or estimated CrCl. The calculator’s color scale follows them.
| Category | CrCl (mL/min) | What it usually means for medicines |
|---|---|---|
| Normal | 90 or higher | Standard doses for most renally cleared drugs. |
| Mild decrease | 60 to 89 | Few changes, though some drugs start adjusting at 60. |
| Moderate decrease | 30 to 59 | The most common zone for label dose reductions. |
| Severe decrease | 15 to 29 | Many drugs need lower doses; some should be avoided. |
| Kidney failure | Below 15 or on dialysis | Dialysis-specific dosing; estimating equations are unreliable. |
What is a normal creatinine clearance by age?
Measured 24-hour urine clearance in healthy adults is commonly quoted as roughly 97 to 137 mL/min for men and 88 to 128 mL/min for women, though every lab sets its own reference range. Clearance tends to fall with age. In the Baltimore Longitudinal Study of Aging, the average decline was about 0.75 mL/min per year, yet around a third of participants showed no meaningful drop at all. So a CrCl of 55 mL/min at age 85 is common, but it is not automatically “normal,” and it still changes how medicines should be dosed.
Creatinine clearance vs eGFR: which one matters?
They answer related but different questions, and mixing them up is one of the most frequent errors I see on prescriptions.
| Feature | Cockcroft-Gault CrCl | eGFR (CKD-EPI 2021) |
|---|---|---|
| Units | mL/min (absolute) | mL/min/1.73 m² (indexed) |
| Uses body weight | Yes | No |
| Main use | Drug dosing from older labels | Diagnosing and staging chronic kidney disease |
| Reported by labs | Rarely, needs calculating | Usually, automatically |
| Where it goes wrong | Obesity, frailty, low muscle mass | Very small or very large bodies if not de-indexed |
The direction of travel is toward eGFR. The FDA’s final guidance from March 2024 favors eGFR for new drug studies, and the National Kidney Foundation now encourages moving medication decisions to race-free eGFR. In daily practice, though, hundreds of existing drug labels still state their cut-offs in CrCl, so pharmacists keep calculating it. When a label names CrCl, use CrCl. When it names eGFR, as metformin’s does, use eGFR. If you do use eGFR for dosing, convert it to an absolute value by multiplying by the patient’s body surface area and dividing by 1.73.
Common drug dosing cut-offs based on CrCl
These examples show how often the numbers 15, 30, 50, and 60 appear on real labels. They are for orientation only. Doses differ by indication and country, so always check the current prescribing information.
| Medicine | CrCl cut-offs on the US label | What changes |
|---|---|---|
| Rivaroxaban (atrial fibrillation) | Above 50 / 15–50 / below 15 | 20 mg daily, then 15 mg daily, then avoid |
| Dabigatran (atrial fibrillation) | Above 30 / 15–30 / below 15 | 150 mg twice daily, then 75 mg twice daily, then not recommended |
| Edoxaban (atrial fibrillation) | Above 95 / 51–95 / 15–50 | Not recommended, then 60 mg, then 30 mg daily |
| Enoxaparin | Below 30 | Reduced treatment and prophylaxis doses |
| Gabapentin | 60 / 30 / 15 | Stepwise daily dose reductions at each band |
| Levofloxacin | 50 / 20 / 10 | Longer dosing interval and lower follow-up doses |
| Nitrofurantoin (older adults) | Below 30 | AGS Beers Criteria advise avoiding it |
| Metformin | Uses eGFR, not CrCl | Not started at eGFR 30–45; contraindicated below 30 |
Should you round serum creatinine up to 1.0 in older adults?
Many hospitals still round a low creatinine, say 0.6 mg/dL in a frail 88-year-old, up to 0.8 or 1.0 before calculating CrCl. The logic is fair: low muscle mass keeps creatinine low, which can make kidney function look better than it is. The evidence, however, doesn’t back the habit. A systematic review of older-adult studies found that every included study produced inaccurate estimates after rounding, and a 2024 vancomycin study in elderly patients linked rounding to underestimated clearance and under-dosing.
My practical approach: calculate with the real value first, then look at the patient. If they are bed-bound, amputated, or visibly wasted, treat the result as a ceiling rather than a fact and lean on drug levels or a measured clearance for narrow-margin drugs. That is why rounding sits behind an optional setting in this calculator instead of running silently.
When the Cockcroft-Gault estimate can mislead you
Any equation built on serum creatinine assumes creatinine production is steady and typical. When that assumption breaks, the number breaks with it:
- Acute kidney injury. Creatinine lags behind a sudden drop in filtration, so a rising value overestimates real clearance. Wait for a stable level or dose conservatively.
- Low muscle mass. Frailty, amputation, paralysis, liver cirrhosis, and long hospital stays all lower creatinine and inflate CrCl.
- High muscle mass. Bodybuilders and heavy manual workers produce more creatinine, which can make clearance look worse than it is.
- Creatine supplements. This one comes straight from my supplement work. Creatine monohydrate at typical doses can nudge serum creatinine upward without harming the kidneys, which lowers the calculated CrCl. Mention it to whoever orders your labs.
- Large cooked-meat meals. Cooking converts muscle creatine into creatinine, and a big meat meal before a blood draw can raise the result temporarily.
- Drugs that block creatinine secretion. Trimethoprim, cimetidine, dolutegravir, bictegravir, and cobicistat can raise serum creatinine modestly without changing true filtration.
- Pregnancy, children, and dialysis. The equation isn’t validated for these groups. Children need a pediatric equation such as bedside Schwartz, and dialysis patients follow dialysis-specific dosing.
How to use this creatinine clearance calculator
- Choose sex, then enter age. The tool accepts adults from 18 to 110.
- Enter weight and height in kg/cm or lb/ft-in. Height unlocks ideal and adjusted weight.
- Enter serum creatinine from a recent, stable lab report, choosing mg/dL or µmol/L to match the report.
- Leave dosing weight on Auto unless your institution specifies a method.
- Read the result in context: the scale position, the three-weight comparison, the creatinine thresholds, and the label cut-offs.
- Open the step-by-step calculation if you need to document or double-check the math.
From the pharmacy counter
Most kidney-related dosing problems I’ve caught weren’t caused by bad math. They came from the inputs: a weight copied from a chart that was two years old, a creatinine drawn on the day of an acute illness, or a µmol/L value typed into an mg/dL box. That last mistake shrinks CrCl by a factor of about 88, and I’ve seen it in real prescriptions. It is why this calculator flags implausible creatinine values instead of accepting them quietly.
The other pattern is age. An older woman with a “normal” creatinine of 0.9 mg/dL can easily have a CrCl in the 30s once her age and weight are factored in. If you care for an elderly parent, bring their current weight and latest creatinine to the pharmacy and ask for a CrCl check on every renally cleared medicine. It takes a pharmacist two minutes and prevents a surprising number of falls, bleeds, and confusion episodes.
Related health calculators
These tools answer the questions that usually come up right after a CrCl check.
You can browse the full set of tools in the dexocalc health calculators hub.
Frequently asked questions
Healthy adults typically fall between about 90 and 140 mL/min. Commonly cited 24-hour urine reference ranges are roughly 97 to 137 mL/min for men and 88 to 128 mL/min for women, and values usually drift lower with age.
Use the Cockcroft-Gault equation: (140 − age) × weight in kg, divided by (72 × serum creatinine in mg/dL). Multiply by 0.85 for females. The answer is in mL/min.
No. Both estimate kidney filtration, but CrCl uses body weight and is reported in mL/min, while eGFR ignores weight and is indexed to 1.73 m². CrCl drives dosing on many older drug labels; eGFR is used to diagnose and stage chronic kidney disease.
A CrCl below 30 mL/min indicates severely reduced kidney function, and below 15 mL/min indicates kidney failure. Both need specialist care and careful review of every medication. A sudden drop from your usual value also deserves prompt medical attention.
Evidence supports actual weight in underweight and normal-weight adults and adjusted body weight (with a 0.4 factor) in overweight or obese adults. Some drugs, including the direct oral anticoagulants, were studied with actual weight, so follow the label or your institution’s protocol.
Divide µmol/L by 88.4. For example, 110 µmol/L equals about 1.24 mg/dL. This calculator converts automatically when you select µmol/L.
Kidney filtration and muscle mass both tend to decline with age, and the (140 − age) term in the formula reflects that. An older person can have a normal-looking creatinine and still have a CrCl low enough to need dose changes.
Yes. Creatine supplements can raise serum creatinine slightly, which lowers calculated CrCl even when kidney function is unchanged. Tell your clinician if you take creatine so they can interpret the result correctly, or ask about a cystatin C test.
No. Cockcroft-Gault was developed in adults and isn’t validated for children. Pediatric kidney function is usually estimated with the bedside Schwartz equation, which uses height instead of weight.
Not reliably. It assumes a stable creatinine. During acute kidney injury, creatinine rises after filtration has already fallen, so the equation overestimates true clearance until levels settle.
It can, particularly after an acute cause is treated, such as dehydration, a urinary blockage, or a medicine that strained the kidneys. Managing blood pressure and blood sugar helps slow further decline in chronic kidney disease, but lost function isn’t always recoverable.
It measures clearance directly rather than estimating it, which helps in people with unusual muscle mass or diet. Its accuracy depends on a complete collection, and incomplete samples are common, so it isn’t automatically better.
Pharmacist and health content writer
Manzoor is a Doctor of Pharmacy with more than nine years of experience in community pharmacy and in writing about medicines and supplements. He runs a community pharmacy, where renal dose checks are part of everyday practice, and builds the health calculators on dexocalc.com so the formulas pharmacists use are available, and explained, for everyone. Read Manzoor’s full profile.
References
- Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron. 1976;16(1):31–41. PubMed
- US Food and Drug Administration. Pharmacokinetics in Patients with Impaired Renal Function — Study Design, Data Analysis, and Impact on Dosing. Final guidance, March 2024. FDA
- Wilhelm SM, Kale-Pradhan PB. Estimating creatinine clearance: a meta-analysis. Pharmacotherapy. 2011;31(7):658–664. PubMed
- Impact of weight and creatinine adjustments on the accuracy of the Cockcroft-Gault equation in hematopoietic cell transplant patients. PubMed
- Older adult kidney function assessment and rounding creatinine: a systematic review. PubMed
- Comparing actual and rounded serum creatinine for vancomycin dosing in elderly patients. 2024. PMC
- National Kidney Foundation. Race-agnostic eGFR for medication-related decisions in adults. kidney.org
- ClinCalc. Creatinine Clearance Calculator: body weight selection and obesity adjustment. clincalc.com
Medical disclaimer: This calculator provides an estimate for education and to support, not replace, professional judgment. It does not diagnose kidney disease or set medication doses. Always confirm dosing with a licensed pharmacist or prescriber using the current product label, and seek urgent care for symptoms such as sharply reduced urine output, swelling, or confusion.