Free GFR Calculator — Check Your Kidney Function Instantly (eGFR)

The Formula

The 2021 CKD-EPI equation estimates glomerular filtration rate from serum creatinine without a race coefficient. The original 2009 and 2012 equations included a race factor that was removed in 2021 when evidence showed it systematically overestimated kidney function in Black patients, potentially delaying care.

Variable Definitions

How to Use This Calculator

1. 1

   Enter your serum creatinine value from a recent lab test.

2. 2

   Select the correct unit (mg/dL is standard in the US, μmol/L in most other countries).

3. 3

   Enter your age and sex.

4. 4

   Review your eGFR and CKD stage.

5. 5

   Discuss results with your healthcare provider — this is a screening estimate, not a diagnosis.

Common Applications

• Kidney disease screening — use eGFRA blood test-based estimate of kidney function. Lower values may indicate chronic kidney disease. from the 2021 CKD-EPI race-free equation to assess kidney function and detect early-stage chronic kidney disease
• CKD staging and monitoring — track eGFRA blood test-based estimate of kidney function. Lower values may indicate chronic kidney disease. trends over time to determine CKD stage and guide treatment planning with a nephrologist
• Medication safety review — healthcare providers check eGFRA blood test-based estimate of kidney function. Lower values may indicate chronic kidney disease. before prescribing renally cleared medications (e.g., metformin, some antibiotics) to adjust dosing appropriately
• Pre-operative assessment — eGFRA blood test-based estimate of kidney function. Lower values may indicate chronic kidney disease. is routinely checked before surgery to assess kidney function and anesthetic risk, especially in patients with diabetes or hypertension

CKD-EPI 2021 equation estimates eGFR from serum creatinine, age, and sex without race coefficient

Understanding the Concept

The Glomerular Filtration Rate (GFR) is the best overall measure of kidney function. The 2021 CKD-EPI equation is the current clinical standard recommended by the National Kidney Foundation and the American Society of Nephrology. It replaced older equations that included race coefficients, which were found to overestimate GFR in Black individuals and contribute to disparities in kidney disease diagnosis and treatment. eGFRA blood test-based estimate of kidney function. Lower values may indicate chronic kidney disease. below 60 mL/min/1.73m² for 3+ months indicates chronic kidney disease. An eGFRA blood test-based estimate of kidney function. Lower values may indicate chronic kidney disease. of 15 or lower indicates kidney failure, requiring dialysis or transplant consideration. eGFRA blood test-based estimate of kidney function. Lower values may indicate chronic kidney disease. is affected by age (declines naturally after ~40), hydration status, muscle mass, certain medications, and acute illness — a single abnormal result should be confirmed with repeat testing. For example, a 65-year-old with an eGFRA blood test-based estimate of kidney function. Lower values may indicate chronic kidney disease. of 68 might be experiencing normal age-related decline rather than kidney disease, while a 30-year-old with the same eGFRA blood test-based estimate of kidney function. Lower values may indicate chronic kidney disease. would likely need further investigation. Serum creatinine, the lab value used in the equation, is itself affected by muscle mass: a bodybuilder may have elevated creatinine (and thus appear to have lower eGFRA blood test-based estimate of kidney function. Lower values may indicate chronic kidney disease.) simply because they have more muscle mass producing more creatinine as a metabolic waste product. This is why cystatin C-based GFR estimates are sometimes used as a confirmatory test in people with very high or very low muscle mass. Other factors that can temporarily lower eGFRA blood test-based estimate of kidney function. Lower values may indicate chronic kidney disease. include dehydration, high-protein meals before blood draws, recent strenuous exercise, and certain medications like NSAIDs (ibuprofen, naproxen) and ACE inhibitors.

Frequently Asked Questions

Sources & References