Creatinine Clearance Calculator (Cockcroft-Gault)
Use this creatinine clearance calculator to estimate your kidney function using the Cockcroft-Gault equation.
Updated October 22, 2026
Medical Disclaimer: This calculator gives a general estimate for education only and cannot diagnose a condition. Share your result with your doctor or the clinician who ordered your test, and do not start, stop or change any medicine based on it. Read our full Medical Disclaimer.
How Creatinine Clearance Is Calculated
Creatinine clearance is the volume of blood plasma your kidneys clear of creatinine, a waste product from muscle, each minute, given in mL/min. Cockcroft-Gault was published in 1976 as a practical way to estimate kidney function from routine labs, without needing a timed urine collection. It remains in wide use nearly 50 years later for one specific reason: much of the drug dosing literature, package inserts, and clinical guidance in use today was calibrated against this exact formula, not a newer one¹.
What This Calculator Measures
This estimates creatinine clearance in mL/min from age, sex, weight, and serum creatinine, with a choice of which weight basis to use, since the formula wasn't derived from a population with a wide obesity range.
The Formula
Creatinine Clearance (mL/min) = [(140 − Age) × Weight (kg)] ÷ (72 × Serum Creatinine [mg/dL])
Multiplied by 0.85 for women.
How This Calculator Computes Your Result
Enter age, sex, weight, and serum creatinine. Choose which weight to use, actual, ideal, or adjusted body weight, since Cockcroft-Gault can meaningfully overestimate clearance in obesity if actual weight is used uncritically. This calculator makes that choice explicit rather than silently defaulting to actual weight for everyone, reusing the same Devine ideal-body-weight and 0.4 adjustment-factor formulas already established on this site's calculators for ideal weight and adjusted body weight.
Why the Choice of Formula Genuinely Matters, Not Just as a Technicality
Cockcroft-Gault and the newer CKD-EPI equation don't just differ slightly, they diverge in predictable, clinically meaningful directions. Research comparing the formulas with measured kidney function found that Cockcroft-Gault's error grows with body weight and BMI, which CKD-EPI's does not². In older adults, Cockcroft-Gault usually gives lower values than CKD-EPI³. In other words, the two formulas don't just disagree randomly, they disagree in predictable directions depending on the patient.
This isn't a minor academic distinction. A study of atrial fibrillation patients on the blood thinner dabigatran found that patients whose dose was higher than Cockcroft-Gault would recommend had more than double the risk of a hemorrhagic event compared with those on the recommended dose (hazard ratio 2.32). CKD-EPI often overestimated kidney function in older patients, which pointed toward those higher doses³. Which formula a clinician uses is a real decision with real downstream consequences, not an interchangeable technical detail.
A Note on Accuracy
Cockcroft-Gault was derived from a specific historical population and is known to be less accurate in extremes of body weight, the elderly, and in those with rapidly changing kidney function. It was not designed for and should not be used in acute kidney injury. This uses the numbers on your lab report. It cannot diagnose a condition, and it should never be used to adjust a medication dose without a clinician's involvement. Ask the clinician who ordered the test what your result means for you.
Frequently Asked Questions
How is this different from eGFR?
eGFR (CKD-EPI) is a separate, methodologically different kidney function estimate, and is now generally preferred for kidney function staging in most clinical contexts. Cockcroft-Gault remains relevant primarily because many existing drug dosing guidelines were calibrated to it specifically, and the two formulas diverge in predictable directions with age and body weight², they're related but not interchangeable.
Why does this ask which weight to use?
Cockcroft-Gault was derived from a population without a wide obesity range. Some clinical contexts use ideal or adjusted body weight instead of actual weight for obese patients, this substitution matters, so the tool makes the choice explicit rather than silently defaulting to actual weight for everyone.
Does the choice of formula actually affect real outcomes?
Yes, demonstrably. A study of patients on a commonly prescribed blood thinner found that people whose dose was higher than Cockcroft-Gault would recommend had more than double the risk of a serious bleeding event. The newer CKD-EPI formula often overestimated kidney function in older patients, which pointed toward those higher doses³. Formula choice is a genuine clinical decision, not a technicality.
Can I use this number to adjust my own medication dose?
No. This estimates kidney function, it does not diagnose any condition, and should never be used to adjust an actual medication dose without a clinician's involvement.
Sources
Prediction of Creatinine Clearance from Serum Creatinine, Cockcroft & Gault, Nephron, 1976
Performance of the Cockcroft-Gault, MDRD, and New CKD-EPI Formulas in Relation to GFR, Age, and Body Size, Michels et al., Clinical Journal of the American Society of Nephrology, 2010
Choice of Renal Function Estimator Influences Adverse Outcomes with Dabigatran Etexilate in Patients with Atrial Fibrillation, Simpson et al., TH Open, 2018