eGFR Calculator
Estimated Glomerular Filtration Rate — CKD-EPI 2021 Equation (Race-Free)
What Is eGFR?
The Glomerular Filtration Rate (GFR) is the best overall measure of kidney function. It measures how much blood your kidneys filter each minute, expressed in milliliters per minute per 1.73 square meters of body surface area (mL/min/1.73m²).
Because directly measuring GFR requires complex, time-consuming tests involving the infusion and clearance of special markers (such as inulin), clinicians use an estimated GFR (eGFR) calculated from a simple blood test. The eGFR provides a reliable approximation for most patients.
What Is Creatinine?
Creatinine is a waste product produced by normal muscle metabolism. It is released into the bloodstream at a relatively constant rate and filtered out by the kidneys. When kidney function declines, creatinine levels in the blood rise because the kidneys can no longer filter it efficiently. By measuring serum creatinine and accounting for age and sex, the CKD-EPI equation estimates the GFR.
How Do the Kidneys Filter Blood?
Each kidney contains approximately one million tiny filtering units called nephrons. Each nephron contains a glomerulus — a cluster of tiny blood vessels — and a tubule. The glomerulus filters the blood, letting water and small waste molecules pass through while retaining blood cells and large proteins. The tubule then reabsorbs needed substances and sends the remaining waste to the bladder as urine. Healthy kidneys filter about 200 liters of blood daily, producing roughly 1–2 liters of urine.
Why the CKD-EPI 2021 Equation?
This calculator uses the CKD-EPI 2021 (race-free) equation, recommended by the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN). The 2021 update removed the race coefficient present in earlier equations, providing a single equation for all patients regardless of race. This approach was adopted because race is a social — not biological — construct, and using race in clinical equations can perpetuate health disparities.
The 5 Stages of Chronic Kidney Disease
Stage G1 — Normal or High (eGFR ≥ 90)
Kidney function: Normal or high filtration rate, but other signs of kidney damage may be present (e.g., protein in urine, structural abnormalities).
Symptoms: Usually none. CKD at this stage is typically detected through routine screening.
Management: Address underlying causes (e.g., diabetes, hypertension). Monitor annually. Maintain a healthy lifestyle.
Prognosis: With proper management, kidney function can often be preserved for many years.
Stage G2 — Mildly Decreased (eGFR 60–89)
Kidney function: Mildly reduced filtration. Like G1, other evidence of kidney damage is needed for a CKD diagnosis at this level.
Symptoms: Usually none. Some patients may notice slightly increased urination at night.
Management: Control blood pressure (target <130/80 mmHg). Manage diabetes carefully. Avoid nephrotoxic medications when possible.
Prognosis: With good control of risk factors, progression can be significantly slowed.
Stage G3a — Mildly to Moderately Decreased (eGFR 45–59)
Kidney function: Moderately reduced. Waste products may begin to accumulate in the blood.
Symptoms: Fatigue, mild swelling in hands or feet, changes in urination patterns, mild back pain.
Management: More frequent monitoring (every 3–6 months). Dietary adjustments may be recommended. Medication review to avoid kidney-harming drugs.
Prognosis: Increased risk of progression. Early intervention is critical.
Stage G3b — Moderately to Severely Decreased (eGFR 30–44)
Kidney function: Significantly reduced. Complications such as anemia, bone disease, and electrolyte imbalances become more common.
Symptoms: Increased fatigue, loss of appetite, nausea, swelling, difficulty concentrating, muscle cramps.
Management: Nephrology referral recommended. Dietary restrictions (phosphorus, potassium, sodium). Treatment of complications. Blood pressure and blood sugar optimization.
Prognosis: Higher risk of progressing to kidney failure. Close medical supervision essential.
Stage G4 — Severely Decreased (eGFR 15–29)
Kidney function: Severely reduced. The kidneys are struggling to maintain fluid balance and filter waste.
Symptoms: Pronounced fatigue, nausea and vomiting, metallic taste, itching, shortness of breath, poor appetite, cognitive changes.
Management: Active nephrology care. Preparation for renal replacement therapy (dialysis or transplant). Strict dietary management. Anemia treatment (EPO, iron). Bone disease management.
Prognosis: High likelihood of progressing to kidney failure. Planning for dialysis or transplant should begin.
Stage G5 — Kidney Failure (eGFR < 15)
Kidney function: Very severely reduced or failed. The kidneys can no longer sustain life without intervention.
Symptoms: Severe fatigue, widespread swelling, very poor appetite, confusion, decreased urine output, shortness of breath at rest, chest pain.
Management: Dialysis (hemodialysis or peritoneal dialysis) or kidney transplant. Intensive medical management of all complications.
Prognosis: Without renal replacement therapy, this stage is life-threatening. With dialysis or transplant, many patients lead meaningful lives.
Protecting Your Kidney Health
Regardless of your current eGFR, adopting kidney-friendly habits can help preserve and protect your kidney function:
- Stay hydrated: Drink adequate water throughout the day (typically 6–8 glasses). Proper hydration helps your kidneys clear sodium, urea, and toxins from the body. However, if you have advanced CKD, your doctor may recommend fluid restriction.
- Control blood pressure: High blood pressure is the second leading cause of kidney disease. Target blood pressure below 130/80 mmHg. Take prescribed antihypertensive medications consistently. ACE inhibitors and ARBs are often preferred because they also protect the kidneys.
- Manage diabetes: Diabetes is the leading cause of CKD. Keep your HbA1c below 7% (or as recommended by your provider). Monitor blood sugar regularly. SGLT2 inhibitors have shown kidney-protective benefits beyond blood sugar control.
- Avoid NSAIDs: Non-steroidal anti-inflammatory drugs (ibuprofen, naproxen, aspirin in high doses) can reduce blood flow to the kidneys and cause damage with prolonged use. Use acetaminophen (Tylenol) for pain when possible, and always consult your doctor before taking any over-the-counter pain medication.
- Reduce sodium intake: Limit sodium to less than 2,300 mg per day (ideally under 1,500 mg for those with CKD or hypertension). Read food labels carefully. Cook at home with fresh ingredients. Use herbs and spices instead of salt.
- Exercise regularly: Aim for at least 150 minutes of moderate-intensity exercise per week. Regular physical activity helps control blood pressure, blood sugar, and body weight — all of which protect kidney function.
- Quit smoking: Smoking reduces blood flow to the kidneys and accelerates CKD progression. It also increases the risk of kidney cancer.
- Limit alcohol: Excessive alcohol consumption can cause acute kidney injury and worsen chronic kidney conditions. Stick to moderate drinking guidelines (up to 1 drink/day for women, 2 for men).
When Should You See a Nephrologist?
A nephrologist is a physician who specializes in kidney care. You should be referred to or seek a nephrologist if you have:
- eGFR below 45 (Stage G3b or worse): At this level, specialized kidney management is recommended to slow progression and manage complications such as anemia, mineral bone disease, and metabolic acidosis.
- Rapid decline in kidney function: A sustained drop in eGFR of more than 5 mL/min/1.73m² per year, or a significant drop over a short period, warrants urgent nephrology evaluation.
- Significant proteinuria: Persistent protein in the urine (albumin-to-creatinine ratio > 300 mg/g, or urine protein > 500 mg/day) indicates glomerular damage and requires specialist assessment.
- Hematuria (blood in urine): Persistent microscopic or gross hematuria of kidney origin (after urologic causes are excluded) should be evaluated by a nephrologist for possible glomerulonephritis.
- Family history of kidney disease: If you have a family history of polycystic kidney disease (PKD), Alport syndrome, or other hereditary kidney conditions, early nephrology consultation can guide screening and preventive care.
- Difficult-to-control hypertension: If blood pressure remains uncontrolled despite 3 or more antihypertensive medications, a nephrologist can evaluate for secondary causes including renal artery stenosis.
- Electrolyte abnormalities: Persistent abnormalities in potassium, sodium, calcium, or phosphorus that may indicate impaired kidney regulation.
Early referral to a nephrologist has been shown to improve outcomes, slow CKD progression, and better prepare patients if renal replacement therapy becomes necessary.
Frequently Asked Questions
eGFR stands for estimated Glomerular Filtration Rate. It is the best overall measure of how well your kidneys are working. The GFR measures how much blood your kidneys filter per minute. Because directly measuring GFR requires complex testing, clinicians use a formula that estimates GFR from a routine blood test (serum creatinine) combined with your age and biological sex. The result is expressed in mL/min/1.73m². A normal eGFR is typically above 90, while lower values indicate reduced kidney function.
The CKD-EPI 2021 equation is the most current and recommended formula for estimating GFR. Developed by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and published in the New England Journal of Medicine in 2021 by Inker et al., this updated equation removed the race coefficient that was present in the original 2009 CKD-EPI equation. It uses serum creatinine, age, and biological sex to estimate GFR. It is endorsed by the National Kidney Foundation (NKF) and the American Society of Nephrology (ASN) as the standard equation for clinical use.
Previous eGFR equations included a race coefficient that adjusted the result for Black patients, which yielded higher eGFR estimates. This practice was problematic for several reasons: race is a social construct, not a reliable proxy for biological differences in creatinine metabolism; using a race adjustment could delay diagnosis and treatment of CKD in Black patients; and it perpetuated the use of race as a biological variable in medicine. In 2021, the NKF-ASN Task Force recommended removing race from eGFR equations, leading to the adoption of the CKD-EPI 2021 race-free formula used in this calculator.
A normal eGFR is generally 90 mL/min/1.73m² or higher. However, eGFR naturally declines with age. A healthy 20-year-old may have an eGFR around 116, while a healthy 70-year-old may have an eGFR around 75. An eGFR between 60 and 89 is considered mildly decreased and may be normal for older adults if there are no other signs of kidney damage. An eGFR below 60 for three or more months, or any eGFR with signs of kidney damage (such as proteinuria), generally indicates chronic kidney disease.
In some cases, yes. If kidney damage is caused by a reversible condition — such as dehydration, medication side effects, urinary tract obstruction, or acute kidney injury — kidney function may partially or fully recover once the underlying cause is treated. In chronic kidney disease, while lost kidney function generally cannot be restored, progression can be significantly slowed or even halted with proper management: controlling blood pressure and blood sugar, taking prescribed medications (ACE inhibitors, ARBs, SGLT2 inhibitors), maintaining a kidney-friendly diet, staying active, and avoiding nephrotoxic substances.
Testing frequency depends on your CKD stage and risk factors. The KDIGO guidelines recommend: Stage G1–G2 (eGFR ≥ 60): Annually, or as recommended by your provider, especially if you have diabetes or hypertension. Stage G3a (eGFR 45–59): At least every 6 months. Stage G3b (eGFR 30–44): Every 3–6 months. Stage G4 (eGFR 15–29): Every 3 months. Stage G5 (eGFR < 15): Every 1–3 months or as directed by your nephrologist. More frequent testing may be indicated if there is a rapid decline or a change in clinical status.
Medical Disclaimer
This eGFR Calculator is provided for educational and informational purposes only and does not constitute medical advice, diagnosis, or treatment. The CKD-EPI 2021 equation provides an estimate of kidney function and may not be accurate in all clinical situations (e.g., extremes of muscle mass, amputees, acute kidney injury, pregnancy). Results should be interpreted by a qualified healthcare professional in the context of a complete clinical evaluation including urine studies and imaging. If you have concerns about your kidney health, please consult your physician or a nephrologist. All calculations are performed in your browser — no personal data is stored on our servers or shared with any third party.
References
- Inker LA, Eneanya ND, Coresh J, et al. New Creatinine- and Cystatin C–Based Equations to Estimate GFR without Race. N Engl J Med. 2021;385(19):1737-1749. doi:10.1056/NEJMoa2102953.
- Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int Suppl. 2013;3(1):1-150.
- National Kidney Foundation. Frequently Asked Questions about GFR Estimates. Available at: kidney.org.
- Levey AS, Stevens LA, Schmid CH, et al. A New Equation to Estimate Glomerular Filtration Rate. Ann Intern Med. 2009;150(9):604-612. doi:10.7326/0003-4819-150-9-200905050-00006.