GFR Calculator
This calculator is for informational purposes only and is not a substitute for professional medical advice. Consult a healthcare provider for personal health decisions.
CKD-EPI 2021 (race-free) and MDRD reference equations
How eGFR Is Calculated
Glomerular filtration rate (GFR) measures how well kidneys filter waste from blood. Because direct GFR measurement is invasive, clinicians estimate it (eGFR) from serum creatinine, age, and sex. This calculator uses the CKD-EPI 2021 race-free equation as the primary result, with MDRD shown for reference.
CKD-EPI 2021: eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^(−1.200) × 0.9938^age × (1.012 if female). Constants κ and α differ by sex. Creatinine can be entered in mg/dL or µmol/L (divide µmol/L by 88.4 to convert). Higher eGFR generally indicates better kidney function.
Results map to CKD stages: Stage 1 (≥90), Stage 2 (60–89), Stage 3a (45–59), Stage 3b (30–44), Stage 4 (15–29), Stage 5 (<15). A single lab value does not diagnose chronic kidney disease — trends over three months matter, along with urine albumin and clinical context.
The optional MDRD checkbox for Black/African American ancestry applies only to the legacy MDRD reference equation (factor 1.212). CKD-EPI 2021 does not use race adjustment. This tool is for educational purposes only — always consult a healthcare provider for medical interpretation.
Examples
| Example | Result |
|---|---|
| Scr 1.0 mg/dL, male, age 50 | eGFR typically ≥90 (Stage 1–2 range) |
| Scr 88 µmol/L, female, age 60 | Converted and calculated via CKD-EPI |
| Scr 2.5 mg/dL, age 70 | Lower eGFR, higher CKD stage likely |
Frequently asked questions
For most adults, eGFR ≥90 mL/min/1.73m² is considered normal if there is no other evidence of kidney damage. Values naturally decline somewhat with age.
Use whichever unit your lab report shows. The calculator converts µmol/L to mg/dL automatically (÷ 88.4).
No. eGFR is one data point. Diagnosis requires repeated measurements, urine tests, and evaluation by a qualified clinician.