Glomerular filtration rate (GFR) measures how well your kidneys filter waste from blood.
About this calculator
Glomerular filtration rate (GFR) measures how well your kidneys filter waste from blood. Doctors often use estimated GFR (eGFR) from a serum creatinine blood test instead of direct measurement.
This calculator applies the CKD-EPI 2021 equation published by Inker et al. in the New England Journal of Medicine (2021). It replaced the 2009 equation and removed the race-based adjustment, giving a single formula for all adults using creatinine in mg/dL, age, and sex.
Enter your latest creatinine result, age, and sex. You get eGFR in mL/min/1.73m² and a CKD stage label (G1 through G5) for context. Stages G3a and below on repeated tests may warrant further evaluation.
Important: this is an educational screening tool, not medical advice. Creatinine varies with muscle mass, diet, and hydration. One lab value cannot diagnose chronic kidney disease — diagnosis requires repeated tests over at least three months plus clinical review. Athletes and muscular adults may have higher creatinine without kidney damage. Always discuss results with a qualified clinician before changing diet, fluids, or medications.
For general health context, see the [[bmi]] calculator. If you are pregnant, use the [[pregnancy]] calculator and rely on your obstetrician for kidney monitoring.
Common uses
- Understanding an eGFR number on a recent lab report
- Seeing how creatinine 1.2 mg/dL maps to CKD stage for a 55-year-old woman
- Comparing eGFR at different ages with stable creatinine
- Learning what CKD G3a means before a nephrology referral
- Educational use for nursing or pharmacy students studying renal function
Frequently asked questions
What is a normal GFR for adults?
eGFR of 90 mL/min/1.73m² or above is generally considered normal (CKD stage G1). Values 60–89 (G2) may be normal in older adults or early change. Below 60 on repeated tests over three months may indicate chronic kidney disease.
Which formula does this calculator use?
CKD-EPI 2021 creatinine equation (Inker LA et al., N Engl J Med 2021). It uses serum creatinine in mg/dL, age, and sex. It does not use cystatin C or include a race coefficient.
Can I diagnose kidney disease from one eGFR result?
No. Chronic kidney disease requires reduced eGFR below 60 or markers of kidney damage for at least three months, confirmed by a doctor. A single low reading, dehydration, or intense exercise can temporarily shift creatinine.
Why is my creatinine high but eGFR still normal?
Muscular people, heavy protein intake, and certain supplements can raise creatinine without true kidney failure. Age and sex adjust the estimate. Your doctor may repeat the test or add urine albumin and cystatin C.
What should I do if my eGFR is below 60?
Do not panic from one online estimate. Book a follow-up with your doctor for repeat labs, blood pressure review, urine albumin-to-creatinine ratio, and medication check. Do not start restrictive diets or stop prescriptions without medical guidance.