Creatinine Clearance Calculator
Estimate creatinine clearance with the Cockcroft-Gault equation from age, body weight, sex and serum creatinine. Switch between metric and imperial units, enter creatinine in mg/dL or µmol/L, choose actual, ideal or adjusted body weight (with a recommended option for your BMI), and see your BMI, body surface area and a BSA-normalized clearance alongside the headline mL/min result that clinicians use to guide drug dosing.
Formula
Worked example
A 50-year-old man, 175 cm and 70 kg, with a serum creatinine of 1.0 mg/dL: his BMI is about 22.9 so actual weight is used. ((140 − 50) × 70) ÷ (72 × 1.0) = 6300 ÷ 72 ≈ 88 mL/min, normal range.
What creatinine clearance measures
Creatinine is a waste product of normal muscle metabolism that healthy kidneys filter out of the blood at a fairly steady rate. Creatinine clearance estimates the volume of blood your kidneys clear of creatinine each minute, expressed in millilitres per minute, and serves as a practical proxy for the glomerular filtration rate. The Cockcroft-Gault equation, published in 1976, predicts this clearance from a single serum creatinine value together with age, weight and sex, avoiding the need for a cumbersome 24-hour urine collection.
Why age, weight and sex appear in the formula
Serum creatinine alone does not tell the whole story because it depends on how much muscle a person carries. The equation multiplies by body weight as a stand-in for muscle mass, subtracts age from 140 because filtration and muscle bulk both decline over the years, and applies a 0.85 factor for women, who on average have less muscle than men of the same weight. The result is that two people with identical creatinine readings can have quite different clearances once these factors are accounted for.
Actual, ideal or adjusted body weight
Which weight you feed the formula changes the answer, so this calculator offers three choices plus a recommended option. Near a normal BMI, pharmacists often use ideal body weight (the Devine 1974 estimate from height) to avoid letting extra body mass inflate the result. In obesity, an adjusted body weight, ideal weight plus 40 percent of the excess over ideal, is the common compromise so clearance is neither over nor underestimated. The recommended setting picks actual weight when you are underweight or lighter than ideal, ideal weight around normal BMI, and adjusted weight once BMI reaches 30. The weight actually used is always shown so you can see what drives the number.
Units, BMI, BSA and the normalized result
Enter weight and height in metric or imperial, and serum creatinine in mg/dL or µmol/L (the calculator converts µmol/L by dividing by 88.4). From your height and weight it also reports body mass index and body surface area using the Mosteller formula. Because Cockcroft-Gault returns a raw mL/min figure tied to your body size, the calculator additionally shows a BSA-normalized clearance per 1.73 m², which is the convention used when staging chronic kidney disease and comparing across people of different sizes.
How clinicians use the result
Cockcroft-Gault remains the reference many drug labels and pharmacists use to adjust doses of medications that the kidneys eliminate, such as certain antibiotics, anticoagulants and chemotherapy agents. A lower clearance means a drug lingers longer, so doses are reduced to avoid toxicity. The equation is an approximation: it can be misleading at the extremes of body weight, in unstable kidney function, or during pregnancy, where other estimates or measured clearance are preferred. It is also known to overestimate clearance by roughly 10 to 30 percent in many patients.
Kidney function stages by creatinine clearance
| Clearance (mL/min) | Stage | Interpretation |
|---|---|---|
| 90 or more | G1 | Normal |
| 60-89 | G2 | Mildly reduced |
| 30-59 | G3 | Moderately reduced |
| 15-29 | G4 | Severely reduced |
| Under 15 | G5 | Kidney failure |
Approximate stages of chronic kidney disease (CKD) by clearance in mL/min, following NKF/KDIGO categories. Diagnosis also depends on albuminuria and repeat testing.
Frequently asked questions
Should I use actual, ideal or adjusted body weight?
A common convention is actual body weight when you are at or below your ideal weight, ideal body weight around a normal BMI, and adjusted body weight (ideal plus 40 percent of the excess) once BMI reaches about 30. The recommended setting in this calculator applies that logic automatically, but you can override it to match a specific protocol. The weight actually used is shown in the results and the steps.
How is creatinine clearance different from eGFR?
Both estimate kidney filtration, but they use different equations. Cockcroft-Gault estimates creatinine clearance from age, weight, sex and creatinine, and is the long-standing standard for drug dosing. eGFR formulas such as CKD-EPI estimate filtration per 1.73 m² of body surface area and are favoured for staging chronic kidney disease. This calculator also shows a BSA-normalized clearance per 1.73 m² so you can compare the two conventions.
My creatinine is in µmol/L, what do I enter?
Switch the serum creatinine unit to µmol/L and enter the value directly; the calculator converts it to mg/dL internally by dividing by 88.4. For reference, 88.4 µmol/L equals 1.0 mg/dL. You can also enter mg/dL by leaving the unit on its default.
Does this replace a doctor’s assessment?
No. This is a general estimate for healthy adults and can be inaccurate at very high or low body weight, in rapidly changing kidney function, or in pregnancy. It is known to overestimate clearance in many people. Use it for context only and discuss any concerning result, or any change to your medications, with a qualified clinician.