# GFR Calculator (Estimated Glomerular Filtration Rate)

Calculate your estimated GFR using the CKD-EPI 2021 equation. Get your CKD stage and kidney function assessment based on creatinine, age, and gender.

## What this calculates

The Glomerular Filtration Rate (GFR) is the best overall measure of kidney function. This calculator uses the CKD-EPI 2021 equation (race-free version) to estimate your GFR from serum creatinine, age, and gender, and provides your CKD (Chronic Kidney Disease) stage.

## Inputs

- **Serum Creatinine** (mg/dL) — min 0.1, max 30
- **Age** (years) — min 18, max 120
- **Gender**

## Outputs

- **Estimated GFR** — Estimated glomerular filtration rate
- **CKD Stage** — formatted as text — Chronic Kidney Disease stage classification
- **Kidney Function** — formatted as text — Description of kidney function level

## Details

The CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) 2021 equation is the current standard for estimating GFR. It replaced the earlier CKD-EPI 2009 equation that included a race coefficient, which has been removed to reduce health disparities. The formula uses serum creatinine (a waste product from muscle metabolism filtered by the kidneys), age, and gender to estimate how efficiently your kidneys filter blood.

A normal GFR is approximately 90–120 mL/min/1.73m². Values below 60 sustained for 3 or more months indicate chronic kidney disease. CKD is classified into 5 stages (G1–G5) based on eGFR level, with additional albuminuria categories (A1–A3) providing further risk stratification. Early stages are often asymptomatic, making regular screening important for at-risk populations (diabetes, hypertension, family history of kidney disease).

This calculator provides estimates for informational purposes. eGFR from creatinine can be affected by muscle mass, diet, medications, and acute illness. Cystatin C-based eGFR equations may be more accurate in certain populations. Always discuss your results with a healthcare provider.

## Frequently Asked Questions

**Q: What is a normal GFR?**

A: A normal GFR is approximately 90–120 mL/min/1.73m², though it naturally declines with age (about 1 mL/min per year after age 30). An eGFR above 90 with no other signs of kidney damage is considered normal.

**Q: Why was the race coefficient removed from the CKD-EPI equation?**

A: The 2021 CKD-EPI update removed the race coefficient because it was based on limited data, perpetuated health disparities, and the use of race as a biological variable in clinical algorithms has been widely criticized. The race-free equation provides equitable care while maintaining accuracy.

**Q: Can GFR improve?**

A: In some cases, yes. Acute kidney injury can resolve with treatment. For chronic kidney disease, progression can be slowed or stabilized through blood pressure control, blood sugar management (for diabetics), medications like ACE inhibitors or ARBs, dietary changes, and avoiding nephrotoxic substances. However, significant GFR recovery in advanced CKD is uncommon.

**Q: What factors can affect the accuracy of eGFR?**

A: eGFR from creatinine may be inaccurate in people with extreme muscle mass (bodybuilders, amputees), those following high-protein or vegetarian diets, acute kidney injury (changing creatinine), pregnancy, and when taking medications that affect creatinine secretion (e.g., trimethoprim, cimetidine).

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Source: https://vastcalc.com/calculators/health/gfr
Category: Health & Fitness
Last updated: 2026-04-21