Creatinine Clearance (CrCl) Calculator

How to Calculate Creatinine Clearance

1. Enter age, sex, weight, and serum creatinine in the units printed on your lab report (mg/dL or µmol/L).
2. Choose a body-weight method, or keep the automatic default that applies the dosing-weight rule.
3. Read the result in mL/min with its interpretation band, then check renal drug dosing.

All four inputs appear on a routine visit or basic blood panel. Age drives the (140 − age) term, so clearance falls steadily across adulthood even when the lab value looks unchanged. Sex applies the 0.85 female factor that accounts for lower average muscle mass. Weight should be the right dosing weight (actual, ideal, or adjusted) rather than always the number on the scale. And serum creatinine, in mg/dL or µmol/L, is the filtration marker in the denominator.

This calculator estimates creatinine clearance with the Cockcroft-Gault equation from age, sex, weight, and serum creatinine, in mg/dL or µmol/L. It returns the result in mL/min and shows how to apply it to renal drug dosing.

What Is Creatinine Clearance?

Creatinine clearance is the volume of blood the kidneys clear of serum creatinine each minute, expressed in mL/min. It estimates kidney filtration and is the value clinicians use most often to dose renally-cleared medications. Creatinine is a waste product the body forms when muscle breaks down creatine phosphate, and the kidneys filter almost all of it from the blood. A healthy adult clears creatinine at roughly 90 to 140 mL/min.

Why Creatinine Clearance Matters

Creatinine clearance matters because two clinical jobs depend on it: drug dosing and early recognition of reduced kidney function. The kidneys filter waste, balance fluid and electrolytes, and clear many medications from the body. Creatinine is produced at a fairly steady rate and removed almost entirely by the kidneys, so the rate at which it is cleared is a practical measure of that filtering work. When the kidneys slow down, renally-cleared drugs accumulate, so many are dosed in clearance bands to avoid toxicity. Reduced kidney function is worth recognising early, when there is the most to protect. A creatinine clearance is more informative than the raw creatinine value alone because it folds in age, sex, and body size, the factors that set how much creatinine a person makes.

The Cockcroft-Gault Formula in Brief

The calculator uses the Cockcroft-Gault equation, which Donald Cockcroft and Henry Gault published in the journal Nephron in 1976:

CrCl (mL/min) = [(140 − age) × weight in kg] ÷ (72 × serum creatinine in mg/dL), × 0.85 if female

For example, a 65-year-old man weighing 80 kg with a serum creatinine of 1.1 mg/dL has a creatinine clearance of [(140 − 65) × 80] ÷ (72 × 1.1) = 6,000 ÷ 79.2 ≈ 76 mL/min. That falls in the mildly reduced band, even though many would read his creatinine as normal. For a woman of the same age, weight, and creatinine, the 0.85 factor lowers the result to about 64 mL/min. Serum creatinine is reported in mg/dL in the United States and in µmol/L across most other countries; divide µmol/L by 88.4 to get mg/dL. The calculator accepts either unit, or use the creatinine unit converter.

For the derivation, what each term does, protocol variants, and why drug labels still rely on the equation, read Cockcroft-Gault formula explained.

Which Body Weight the Calculator Uses

The weight that goes into the equation depends on how the patient's actual weight compares with their ideal body weight (IBW). IBW comes from the Devine formula: men 50 kg and women 45.5 kg, plus 2.3 kg for every inch of height over 5 feet. The calculator applies this rule:

The evidence column comes from a 2012 study by Winter and colleagues, which compared each weight against measured creatinine clearance. The study grouped patients by weight category rather than by a percentage of IBW, so the 130% line is a practical dividing point, not a number taken from the study. FDA guidance on renal impairment studies (2024) points the same way for overweight and obese people. Some hospitals switch to adjusted body weight at 120% of IBW instead of 130%, so check your local policy. When a drug label or a clinical trial protocol states its own weight rule, that rule takes priority over this one.

Creatinine Clearance Across the Lifespan

Creatinine clearance changes across the lifespan: kidney filtration rises through childhood, plateaus in early adulthood, and then declines by roughly 1 mL/min per year after about age 40 as nephrons are gradually lost. Muscle mass, and therefore creatinine production, falls in parallel, so the serum creatinine value can look unchanged for decades while the underlying clearance steadily drops. That mismatch is the most important reason to estimate clearance rather than read creatinine alone. It is also why an identical creatinine of 1.0 mg/dL implies a healthy clearance in a 30-year-old and a meaningfully reduced one in an 80-year-old. An older adult with a textbook-normal creatinine can therefore still need a reduced medication dose, and a clearance estimate, not the raw lab value, should guide that decision. Compare typical figures on normal creatinine by age and normal eGFR by age.

When Creatinine Clearance Is Most and Least Reliable

The Cockcroft-Gault estimate is most dependable when serum creatinine is stable and muscle mass is typical for the patient. It is least reliable in a few situations. A creatinine that is still rising or falling has not reached steady state, so any estimate from it is provisional. Very high or very low muscle mass (athletes, frailty, amputees) skews the number because creatinine production no longer matches the population average. And acute kidney injury breaks the assumption of a steady state entirely. In those cases, clinicians repeat the test, choose the appropriate dosing weight, or turn to a muscle-independent marker such as cystatin C.

CrCl vs eGFR: Which Should You Use?

Use creatinine clearance for drug dosing and eGFR for CKD staging. Creatinine clearance from the Cockcroft-Gault equation reads in mL/min, and most drug labels and dosing studies were validated against it. Estimated GFR from the CKD-EPI 2021 equation reads in mL/min/1.73m² and stages chronic kidney disease. Read the full breakdown of CrCl vs eGFR.

Creatinine clearance is not the same as GFR either. Glomerular filtration rate counts only what the glomeruli filter, while creatinine clearance also includes the small amount of creatinine the kidney tubules secrete, so it reads slightly higher than true GFR. See why creatinine clearance overestimates GFR for how the gap behaves as kidney function falls.

There is no exact conversion from an eGFR to a creatinine clearance, because the two numbers come from different equations built on different inputs. An eGFR in mL/min/1.73m² can be de-indexed to mL/min by multiplying it by the patient's body surface area and dividing by 1.73, which puts it on the same scale as creatinine clearance. The de-indexed figure is still an eGFR, not a Cockcroft-Gault result. Use the GFR unit converter to de-index a value, and calculate creatinine clearance directly when a drug label asks for it.

Names You May See on a Lab Report

Lab reports, drug labels, and trial protocols use several names for the same estimate: CrCl, ClCr, CLcr, eCrCl, estimated CrCl, and Cockcroft-Gault CrCl. All of them are reported in mL/min, not in mL/min/1.73m². A value in mL/min/1.73m² is an eGFR, and moving between the two scales needs body surface area, as described in the mL/min and mL/min/1.73m² converter.

The phrase modified Cockcroft-Gault has no single meaning. It usually means a local rule was added, such as a cap on body weight or a minimum creatinine value. The SWOG cancer research network's dosing policy is one example: it caps weight at 140% of IBW, uses a minimum serum creatinine of 0.7 mg/dL, and limits the creatinine clearance used for dosing to 125 mL/min. When a report says "modified", read its notes to find out which rule was applied before you compare the result with this calculator.

Using Creatinine Clearance for Renal Drug Dosing

Renally-cleared drugs follow creatinine-clearance dose bands, with lower doses or longer intervals as clearance falls. The same four cut-points recur across drug classes:

These bands are approximate guides: a patient at 31 mL/min is clinically similar to one at 29, so the trend and the drug's therapeutic window matter alongside the number. Each drug also carries its own thresholds. Vancomycin, apixaban, and enoxaparin are dosed differently from one another, and a few agents such as metformin are labelled by eGFR rather than creatinine clearance. See renal drug dosing by creatinine clearance for every agent.

Some labels describe kidney function in words, such as mild, moderate, or severe renal impairment, rather than as a single cut-off. In US labels, these terms map to the renal function categories set out in FDA guidance on studying drugs in people with reduced kidney function, explained in FDA renal impairment categories.

A bare creatinine value rarely changes a prescription, but the clearance it implies frequently does. That is why this site is built to calculate the number, interpret it, and connect it straight to the dose.

Special Populations

The Cockcroft-Gault estimate assumes typical muscle mass and a steady creatinine, so several groups need a deliberate adjustment:

• Elderly patients: low serum creatinine from low muscle mass can overstate clearance. Never round a low creatinine up to 1.0 mg/dL without thought.
• Patients with obesity: total body weight overestimates clearance, so use adjusted body weight or the Salazar-Corcoran equation.
• Pregnancy: plasma volume expansion raises creatinine clearance above non-pregnant ranges, and a lower creatinine is normal.
• Children: the adult equation does not apply; pediatric estimates use the height-based Schwartz equation.
• Amputees and others with atypical muscle: a muscle-independent marker such as cystatin C may estimate filtration more reliably.

Creatinine Clearance vs a 24-Hour Urine Collection

Historically, creatinine clearance was measured by collecting every drop of urine over 24 hours and comparing the creatinine in it with the blood level. That method is accurate but cumbersome and error-prone. A single missed void throws off the result. The Cockcroft-Gault equation estimates the same quantity from a blood test alone, which is why it became the practical standard. The estimate reads slightly higher than true glomerular filtration because the kidney tubules secrete a little creatinine in addition to filtering it. That is the reason creatinine clearance and GFR are related but not identical, as described in the CrCl vs eGFR section above.

A measured 24-hour creatinine clearance is calculated as (urine creatinine × urine volume) ÷ (serum creatinine × collection time). With urine volume in mL and time in minutes, the result is in mL/min, and a full 24-hour collection lasts 1,440 minutes. Urine and serum creatinine must be entered in the same units so that they cancel. For example, a urine creatinine of 100 mg/dL, a urine volume of 1,440 mL, and a serum creatinine of 1.0 mg/dL give (100 × 1,440) ÷ (1.0 × 1,440) = 100 mL/min. Read more about the collection itself under urine creatinine.

Edge Cases: Borderline Results, Lab Timing, and Records

Most calculations are routine. The ones that cause trouble sit close to a dosing or eligibility cut-off, use a creatinine that is changing, or have to be explained later to someone else. The four situations below come up often enough to plan for.

Borderline Results and Rounding

Small input differences move the result across a cut-off. For the 65-year-old man weighing 80 kg in the worked example above, a serum creatinine of 1.8 mg/dL gives 46.3 mL/min and 1.9 mg/dL gives 43.9 mL/min, either side of a 45 mL/min line. Cut-offs at that level are common: in an analysis of pivotal trials for cancer drugs approved from 2015 to 2019, the median lower kidney-function limit for entry was 45 mL/min (or mL/min/1.73m²), with a range of 20 to 60.

When a result such as 44.8 mL/min sits next to a 45 mL/min cut-off:

• Record the unrounded value alongside any rounded figure.
• Apply the rounding rule stated in the drug label or trial protocol. If the document states none, record the value as calculated and flag the borderline result to the prescriber or study team.
• Never change the inputs to reach a cut-off: do not switch weight methods, pick an older creatinine, or round the creatinine to move the result across the line.

Rounding a low serum creatinine up to a fixed value is a separate question. In the Winter study, rounding low creatinine values did not improve the accuracy or bias of Cockcroft-Gault, so apply a creatinine minimum only when a protocol or local policy requires one, as in the SWOG rule described above.

Which Creatinine Result to Use

Use the most recent serum creatinine, and check the date the specimen was drawn, not the date the report was filed or printed. Do not average several results. The Cockcroft-Gault equation assumes kidney function is stable, and an average hides whether creatinine is rising or falling. When creatinine is changing quickly, as in acute kidney injury, the estimate is unreliable, so treat it as provisional and repeat it once creatinine settles. If a trial protocol sets a time window for eligibility labs, the creatinine must fall inside that window.

When Creatinine Clearance Falls During Treatment

Recalculate creatinine clearance each time a new creatinine result arrives, using the same weight rule and an up-to-date weight. A new value can move a patient into a different dose band, for example from above 50 mL/min into the 30 to 50 mL/min band in the table above, and that can change the dose or interval of the renally cleared drugs the patient takes. Recheck each one against its renal dose adjustment thresholds. A fall that is sudden, rather than gradual, is also a prompt to look for a cause, as described in the next steps below.

Recording the Calculation

A creatinine clearance in a chart or study file should let someone else repeat the calculation. Record:

• the inputs with their units: age, sex, weight in kg, height if IBW was used, and serum creatinine in mg/dL or µmol/L with its draw date;
• the weight used (actual, ideal, or adjusted) and why it was chosen;
• the formula, including any local modification such as a weight cap or creatinine minimum;
• the result in mL/min, unrounded, and the date of the calculation.

The Copy summary button in the calculator above copies these details as text you can paste into a note. For research, US regulations (21 CFR 312.62) require investigators to keep adequate and accurate case histories for each participant. Kidney-function criteria are a common part of trial entry: 95% of the pivotal cancer drug trials in the analysis above had kidney-related eligibility criteria, and 64% used estimated creatinine clearance. See creatinine clearance for clinical trial eligibility for what a trial record should contain.

Why We Build on the Gault Standard

We call our methodology the Gault Standard because every calculation follows the validated Cockcroft-Gault lineage, cites primary sources, and is reviewed by a credentialed clinician. Henry Gault, who co-published the equation in 1976, is the historical namesake, not a current reviewer. The aim is a single, trustworthy place to calculate kidney function, interpret the result, and act on it, whether you are a clinician dosing a drug at 2 a.m. or a patient decoding a lab report.

What Your Result Tells You and What to Do Next

A single creatinine clearance is a snapshot, so read it alongside two things: the trend over previous results and the clinical context. A stable value, even a mildly reduced one, is usually managed routinely. A sudden drop, or a decline faster than the roughly 1 mL/min a year expected with age, prompts a closer look for a reversible cause such as dehydration, a new nephrotoxic drug, or acute illness. Whatever the number, two next steps follow almost every time it is calculated. If a medication is involved, check the result against the drug's renal dosing thresholds. If the result is unexpected or persistently low, confirm it on a repeat test. Where staging is the question, pair it with an eGFR and a urine albumin-to-creatinine ratio; together they place a patient on the KDIGO risk map far more reliably than clearance alone. A clearance is never a diagnosis on its own, so act on it with a clinician who knows the rest of the clinical picture.

Related Kidney Function Calculators

• eGFR calculator (CKD-EPI 2021), which stages chronic kidney disease.
• MDRD GFR calculator, an earlier GFR equation.
• BUN/creatinine ratio calculator, which flags dehydration and pre-renal causes.

Our Methodology and Medical Review

Every calculator follows the validated Cockcroft-Gault lineage and cites primary sources, and a credentialed clinician reviews each page. Read about the Gault Standard and our medical reviewers.