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GFR Calculator

Estimate your glomerular filtration rate (eGFR) and assess kidney function using CKD‑EPI 2021, MDRD, and Cockcroft‑Gault formulas.

Required for Cockcroft‑Gault formula.

Estimated GFR (CKD‑EPI 2021)

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mL/min/1.73m²

Formula Comparison

🩺 CKD Staging

Assessment Details

This calculator provides estimates for informational purposes only. Always consult a qualified healthcare provider for interpretation and treatment decisions.

Understanding Glomerular Filtration Rate (GFR)

Glomerular Filtration Rate (GFR) measures how much blood passes through the glomeruli—tiny filters in the kidneys—each minute. It is the best overall indicator of kidney function. A normal GFR is typically above 90 mL/min/1.73m². As kidney function declines, GFR decreases. This Professional GFR Calculator uses the latest 2021 CKD‑EPI (race‑free) equation to estimate your GFR, along with MDRD and Cockcroft‑Gault for comparison, and classifies your result according to CKD staging guidelines.

GFR Estimation Formulas

  • CKD‑EPI 2021: The current gold standard. Uses serum creatinine, age, and gender. More accurate across all GFR ranges, especially near normal values.
  • MDRD (Modification of Diet in Renal Disease): Well‑established; accurate for GFR <60 but may underestimate higher values.
  • Cockcroft‑Gault: Estimates creatinine clearance (CrCl) rather than GFR. Requires body weight. Commonly used for drug dosing adjustments.

💡 CKD Staging (Based on GFR)

Stage 1: GFR ≥90 (normal, but kidney damage present). Stage 2: 60‑89 (mild). Stage 3a: 45‑59, 3b: 30‑44 (moderate). Stage 4: 15‑29 (severe). Stage 5: <15 (kidney failure). Early detection and management can slow progression.

Factors That Influence GFR

  • Age: GFR naturally declines ~1% per year after age 30‑40.
  • Muscle mass: Higher muscle mass raises creatinine, potentially underestimating GFR.
  • Diet: High protein intake or creatine supplements can elevate creatinine.
  • Medications: Some drugs (e.g., trimethoprim, cimetidine) affect creatinine secretion.
  • Hydration: Dehydration can transiently lower GFR.

Frequently Asked Questions

What is a normal GFR for my age?

GFR declines with age. A young adult may have GFR >120; by 60, ~90; by 80, ~70. A GFR <60 for 3+ months indicates CKD regardless of age.

Can GFR improve?

Acute kidney injury (from dehydration, medications) may be reversible. Chronic kidney disease is usually progressive, but its decline can be slowed with blood pressure control, diabetes management, and diet.

Why does the calculator ask for weight?

Weight is only used for the Cockcroft‑Gault formula, which estimates creatinine clearance (CrCl). CKD‑EPI and MDRD do not require weight.

How often should I check my GFR?

If you have risk factors (diabetes, hypertension, family history), annually or as recommended by your doctor. If you have CKD, monitoring may be every 3‑6 months.

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