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
The kidneys filter waste, balance fluid and electrolytes, and clear many medications from the body. Because creatinine is produced at a fairly steady rate and removed almost entirely by the kidneys, how fast it is cleared is a practical window onto that filtering work. Two clinical jobs depend on the answer. The first is drug dosing: when the kidneys slow down, renally-cleared drugs accumulate, so many are dosed in clearance bands to avoid toxicity. The second is recognising reduced kidney function early, when there is the most to protect. A creatinine clearance is more informative than the raw creatinine value alone because it folds in the factors — age, sex, and body size — that change how much creatinine a person makes in the first place.
How the Cockcroft–Gault Equation Works
The Cockcroft–Gault equation estimates creatinine clearance as [(140 − age) × weight in kg × (0.85 if female)] ÷ (72 × serum creatinine in mg/dL). Donald Cockcroft and Henry Gault published this equation in 1976 in the journal Nephron. The equation takes four inputs: patient age in years, body weight in kilograms, biological sex, and serum creatinine. The 0.85 multiplier adjusts for the lower average muscle mass of female patients.
Which Units: mg/dL or µmol/L?
Serum creatinine is reported in mg/dL in the United States and in µmol/L across most other countries. Convert µmol/L to mg/dL by dividing by 88.4. The calculator accepts either unit, so you select the one on the lab report — or use the creatinine unit converter.
Which Body Weight to Use: Total, Ideal, or Adjusted?
Three body-weight methods feed the equation, and the right one depends on the patient's build:
| Body weight | Use when | Note |
|---|---|---|
| Ideal body weight (IBW) | the patient is normal-to-lean | from the Devine formula |
| Adjusted body weight (AjBW) | the patient is obese (>30% over ideal) | improves accuracy in obesity |
| Total body weight (TBW) | actual weight is near ideal | overestimates clearance in obesity |
When actual weight falls below ideal body weight, use the actual weight.
How to Read Your Creatinine Clearance Result
A normal adult creatinine clearance is 90 to 140 mL/min, and it declines steadily with age. The result falls into five interpretation bands:
| Creatinine clearance (mL/min) | Interpretation |
|---|---|
| ≥ 90 | normal-to-high filtration |
| 60–89 | mildly reduced filtration |
| 30–59 | moderately reduced filtration |
| 15–29 | severely reduced filtration |
| < 15 | kidney-failure range |
A result under 60 mL/min changes the dose of many medications. See normal creatinine levels by age for reference values.
What You Need to Calculate Creatinine Clearance
The calculator asks for four values, all of which 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. The calculator also lets you choose the body-weight method automatically, which applies the standard rule for you.
A Worked Example
Take a 65-year-old man weighing 80 kg with a serum creatinine of 1.1 mg/dL. The Cockcroft–Gault equation gives [(140 − 65) × 80 × 1] ÷ (72 × 1.1) = 6,000 ÷ 79.2 ≈ 76 mL/min. That falls in the mildly reduced band, despite a creatinine many would read as normal — a reminder that the same creatinine maps to very different clearances depending on age, sex, and size. For a woman of the same age, weight, and creatinine, the 0.85 factor lowers the result to about 64 mL/min. Enter your own numbers above to see where the result lands and what it means.
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 handful of situations worth recognising: 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.
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 appear again and again across drug classes:
| Creatinine clearance (mL/min) | Typical action |
|---|---|
| > 50 | usually the standard dose |
| 30–50 | reduce the dose or extend the interval for many agents |
| 15–30 | deeper reduction; some drugs are avoided |
| < 15 or dialysis | lowest dosing or an alternative agent |
These bands are guides, not bright lines — 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.
This is the practical reason the calculator exists. A bare creatinine value rarely changes a prescription, but the clearance it implies frequently does — which 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 Across the Lifespan
Kidney filtration is not fixed. It 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. Because muscle mass — and therefore creatinine production — falls in parallel, the serum creatinine value can look unchanged for decades while the underlying clearance steadily drops. That mismatch is the single most important reason to estimate clearance rather than read creatinine alone, and it is 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. For this reason, an older adult with a textbook-normal creatinine can still need a reduced medication dose, and a clearance estimate — not the raw lab value — is what should guide that decision. Compare typical figures on normal creatinine by age and normal eGFR by age.
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 — the reason creatinine clearance and GFR are related but not identical, explained under tubular secretion.
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 figure that is falling faster than the roughly 1 mL/min a year expected with age, or a sudden drop, 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 and, where staging is the question, pair it with an eGFR and a urine albumin-to-creatinine ratio, which together place a patient on the KDIGO risk map far more reliably than clearance alone. A clearance is never a diagnosis on its own — it is a number to act on with a clinician who knows the rest of the picture.
Related Kidney Function Calculators
- eGFR calculator (CKD-EPI 2021) — stages chronic kidney disease.
- MDRD GFR calculator — an earlier GFR equation.
- BUN/creatinine ratio calculator — flags dehydration and pre-renal causes.
Our Methodology & 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.