Creatinine Clearance Calculator: Cockcroft-Gault Equation
Creatinine clearance (CrCl) is an estimate of how much blood the kidneys filter each minute, expressed in millilitres per minute (mL/min). It is calculated from serum creatinine, a metabolic waste product produced at a rate proportional to muscle mass and excreted almost entirely by the kidneys. The Cockcroft-Gault equation, first published in Nephron in 1976, remains the most widely used clinical formula for estimating CrCl because it requires only four routinely available values: age, sex, weight, and serum creatinine. It is the preferred equation for adjusting doses of renally cleared medications such as antibiotics, anticoagulants, and antidiabetics. The female sex multiplier of 0.85 corrects for the fact that women have on average less muscle mass than men of similar age and weight, producing less creatinine for the same degree of kidney function. This calculator takes your inputs, applies the Cockcroft-Gault formula, and maps the result to the National Kidney Foundation's five-stage CKD classification. The CKD stage shown is an approximation: formal staging requires eGFR (not CrCl), evidence of kidney damage lasting more than three months, and clinical assessment. Use this tool to understand your result in context, not as a substitute for advice from a nephrologist or primary care provider.
Estimated creatinine clearance: -- mL/min (--).
The Cockcroft-Gault equation
The formula estimates creatinine clearance in mL/min from four variables available in any routine blood test panel.
CrCl (mL/min) = ((140 - age) x weight_kg x [0.85 if female]) / (72 x serum_creatinine_mg_dL)
The 0.85 multiplier for females accounts for lower average muscle mass compared to males of identical age and weight, which results in less creatinine production per kilogram of body weight.
Worked example
55-year-old female, weight 65 kg, serum creatinine 1.2 mg/dL:
- (140 - 55) = 85
- 85 x 65 = 5,525
- 5,525 x 0.85 (female) = 4,696.25
- 72 x 1.2 = 86.4
- CrCl = 4,696.25 / 86.4 = 54.4 mL/min (Stage 3: moderately decreased)
CKD staging by creatinine clearance
The table below maps CrCl ranges to approximate CKD stages. Formal CKD staging by the National Kidney Foundation uses eGFR, not CrCl. These stages are provided as an approximate reference only.
| CrCl (mL/min) | CKD Stage | Description | Clinical notes |
|---|---|---|---|
| 90 or above | Stage 1 | Normal or high | Kidney damage markers required for CKD diagnosis; CrCl alone is not sufficient |
| 60 to 89 | Stage 2 | Mildly decreased | Often asymptomatic; kidney damage markers also needed for CKD diagnosis |
| 30 to 59 | Stage 3 | Moderately decreased | Risk of complications increases; medication dose adjustments often needed |
| 15 to 29 | Stage 4 | Severely decreased | Preparation for renal replacement therapy may begin |
| Below 15 | Stage 5 | Kidney failure | Dialysis or transplant typically required |
Limitations of the Cockcroft-Gault equation
The equation was derived from a hospital population in the 1970s and has several known limitations. It may overestimate CrCl in obese patients (because actual body weight inflates the numerator), underestimate CrCl in patients with low muscle mass (such as the elderly, malnourished, or those with muscle-wasting conditions), and be inaccurate in patients with acute kidney injury or rapidly fluctuating creatinine levels.
The CKD-EPI (2021) equation is now preferred by the National Kidney Foundation and the American Society of Nephrology for eGFR reporting in clinical laboratories. However, the Cockcroft-Gault equation remains widely used by pharmacists for calculating medication doses because most drug dosing studies used it during their development.
If you have questions about your kidney function or medication dosing, consult a nephrologist, pharmacist, or primary care provider.
Creatinine clearance calculator: frequently asked questions
What is creatinine clearance and why is it important?
Creatinine clearance (CrCl) estimates how efficiently the kidneys filter creatinine, a waste product from muscle metabolism, out of the blood each minute. It is expressed in mL/min. A higher value indicates better kidney function. CrCl is used by clinicians to stage chronic kidney disease (CKD), adjust medication doses for drugs that are cleared by the kidneys, and monitor kidney function over time.
What is the Cockcroft-Gault equation?
The Cockcroft-Gault equation, published by Cockcroft and Gault in 1976, estimates creatinine clearance from age, sex, body weight, and serum creatinine. It remains one of the most widely used equations in clinical practice, particularly for medication dosing. For females, the result is multiplied by 0.85 to account for lower average muscle mass compared to males of the same age and weight.
How is CrCl different from eGFR?
CrCl and estimated glomerular filtration rate (eGFR) are both measures of kidney function but come from different equations. eGFR is typically calculated from the CKD-EPI or MDRD equation and is standardised to a body surface area of 1.73 m2. CrCl from the Cockcroft-Gault equation is not body-surface-area adjusted and is preferred for medication dosing. eGFR is preferred for CKD staging and monitoring by bodies such as the National Kidney Foundation.
What weight should I use in the Cockcroft-Gault equation?
The Cockcroft-Gault equation uses actual body weight for most patients. In obese patients (body weight significantly above ideal body weight), clinicians sometimes use adjusted body weight or lean body weight to avoid overestimating CrCl. If you are uncertain which weight to use, consult a pharmacist or prescribing clinician, particularly when dosing renally cleared medications at narrow therapeutic windows.
Can this calculator diagnose kidney disease?
No. This calculator provides an estimate based on the Cockcroft-Gault equation and the CKD staging framework from the National Kidney Foundation. CKD diagnosis requires a full clinical assessment including multiple blood tests, urinalysis, imaging, and a history of kidney damage lasting more than three months. A single creatinine value does not establish a diagnosis. Always consult a healthcare provider for interpretation of kidney function results.
Official sources
- Cockcroft DW, Gault MH. Prediction of creatinine clearance from serum creatinine. Nephron. 1976;16(1):31-41.
- National Kidney Foundation: About Chronic Kidney Disease.
- National Kidney Foundation: eGFR and CKD staging.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology. General information only, not medical advice.