GFR / eGFR Kidney Function Calculator (CKD-EPI 2021 Race-Free)
Calculate your Estimated Glomerular Filtration Rate (eGFR) and Chronic Kidney Disease (CKD) stage using the official race-free 2021 CKD-EPI Creatinine Equation.
How to Use the GFR / eGFR Kidney Function Calculator (CKD-EPI 2021 Race-Free)
Estimated Glomerular Filtration Rate (eGFR) is the gold-standard clinical indicator of how efficiently your kidneys filter waste products from the bloodstream. Our calculator implements the latest National Kidney Foundation (NKF) and American Society of Nephrology (ASN) 2021 CKD-EPI Refit Creatinine Equation, which removed legacy race-based multipliers to provide an equitable, standardized assessment for all adult patients.
Formula and Calculation Methodology
- S_cr: Standardized serum creatinine level from blood panel (mg/dL)
- κ (kappa): 0.7 for females and 0.9 for males
- α (alpha): -0.241 for females and -0.302 for males
Because serum creatinine is a byproduct of skeletal muscle metabolism, a single creatinine number (such as 1.2 mg/dL) means very different things depending on a person’s age and biological sex. Normalizing filtration to a standard body surface area of 1.73 m² allows physicians and renal dietitians to classify kidney function across Stages 1 through 5.
Clinical Chronic Kidney Disease (CKD) Stages by eGFR (KDIGO Guidelines)
| CKD Stage | eGFR Range (mL/min/1.73m²) | Kidney Function Description | Recommended Action |
|---|---|---|---|
| Stage 1 (G1) | ≥ 90 | Normal or high kidney function | Control BP & blood sugar |
| Stage 2 (G2) | 60 – 89 | Mildly decreased filtration | Annual serum creatinine & uACR check |
| Stage 3a (G3a) | 45 – 59 | Mild-to-moderately decreased | Adjust renally cleared med dosages |
| Stage 3b (G3b) | 30 – 44 | Moderately-to-severely decreased | Screen for anemia & bone mineral labs |
| Stage 4 (G4) | 15 – 29 | Severely decreased function | Nephrologist care planning |
| Stage 5 (G5) | < 15 | Kidney failure / ESRD | Dialysis or transplant preparation |
Frequently Asked Questions
Why can dehydration or high protein intake temporarily lower eGFR?
Dehydration, intense resistance training, cooked meat consumption prior to a blood draw, or creatine supplementation can transiently elevate serum creatinine, making your calculated eGFR appear artificially lower.
What is a normal eGFR for someone over age 60?
While an eGFR above 90 is optimal in young adults, eGFR naturally declines by roughly 0.8 to 1.0 mL/min per year after age 40. An eGFR between 60 and 89 without protein in the urine (albuminuria) is generally considered normal in older adults.
When is Cystatin C used alongside Creatinine for eGFR?
In highly muscular athletes or patients with low muscle mass where serum creatinine may be skewed, doctors order a Cystatin C blood test to run the combined CKD-EPI Creatinine-Cystatin C equation.