GFR Calculator

Category: Other Health
- April 03, 2025
| |

Calculate estimated Glomerular Filtration Rate (eGFR) using the MDRD or CKD-EPI equations. GFR measures how well your kidneys filter blood and helps detect kidney disease.

Patient Information

Laboratory Values

Advanced Options

About GFR and Kidney Function

Glomerular Filtration Rate (GFR) is the best overall measure of kidney function. It estimates how much blood passes through the glomeruli (tiny filters in kidneys) each minute. A declining GFR indicates worsening kidney function.

GFR Classification and CKD Stages
GFR (mL/min/1.73m²) CKD Stage Kidney Function
≥90 Stage 1 (with other evidence of kidney damage) Normal or High
60-89 Stage 2 (with other evidence of kidney damage) Mildly Decreased
45-59 Stage 3a Mildly to Moderately Decreased
30-44 Stage 3b Moderately to Severely Decreased
15-29 Stage 4 Severely Decreased
<15 Stage 5 Kidney Failure
Calculation Methods
  • CKD-EPI Equation (2009): The most accurate method for estimating GFR, especially for higher GFR values (>60 mL/min/1.73m²). Recommended for general clinical use.
  • MDRD Equation (4-variable): An older formula that may underestimate GFR in healthier individuals with values >60 mL/min/1.73m².
Important Notes
  • This calculator provides an estimate of GFR based on serum creatinine. For more accurate kidney function assessment, consult with a healthcare provider.
  • GFR calculations are less reliable at extremes of age and body size.
  • A single GFR measurement should not be used to diagnose kidney disease. Persistent abnormalities for >3 months are needed for chronic kidney disease diagnosis.
  • Additional tests (e.g., urine albumin-to-creatinine ratio) may be needed to fully assess kidney health.

What Is the GFR Calculator?

The GFR Calculator is a simple tool used to estimate the glomerular filtration rate (GFR), a key measure of kidney function. It helps assess how well the kidneys are filtering waste from the blood and is often used to detect or monitor chronic kidney disease (CKD).

By entering a few pieces of personal and laboratory information—such as age, gender, race, and serum creatinine levels—the calculator provides a quick estimate of your kidney function.

CKD-EPI Formula:
GFR = 141 × min(SCr/κ, 1)α × max(SCr/κ, 1)-1.209 × 0.993Age × [Gender Factor] × [Race Factor]

Where:
• κ = 0.7 for females, 0.9 for males
• α = -0.329 for females, -0.411 for males
• SCr = serum creatinine in mg/dL
• Gender Factor = 1.018 if female, 1.0 if male
• Race Factor = 1.159 if Black, 1.0 otherwise

Why Use This Calculator?

This tool is helpful for individuals who want to understand more about their kidney health. It's also commonly used in healthcare settings to support diagnosis and treatment decisions.

The calculator gives:

  • Estimated GFR (eGFR): A numerical value representing kidney filtration rate.
  • CKD Stage: A classification that indicates the level of kidney function.
  • Function Description: Simple terms describing how well the kidneys are working.

How to Use the GFR Calculator

Using the calculator is easy. Follow these steps:

  1. Enter your age in years (must be between 18 and 120).
  2. Select your gender and race.
  3. Choose your preferred calculation method:
    • CKD-EPI: Recommended for most users, especially when eGFR is above 60.
    • MDRD: Older method, less accurate for higher GFR values.
  4. Enter your serum creatinine value. You can choose between mg/dL and μmol/L.
  5. Click the "Calculate GFR" button to see your results.

Optional settings allow you to:

  • Choose how many decimal places to show in the result.
  • Show or hide detailed calculation steps and formulas.

Understanding the Results

Your eGFR result is shown along with an interpretation. This helps you understand if your kidney function is normal, mildly reduced, or severely impaired. A CKD stage and description like “Mildly Decreased” or “Kidney Failure” is also provided for easier understanding.

Keep in mind:

  • GFR values over 90 may still require further tests if other signs of kidney damage are present.
  • One-time GFR values should not be used to diagnose CKD. Persistent changes over time are necessary.

Who Should Use This Tool?

The GFR Calculator is useful for:

  • Patients tracking their kidney health over time.
  • Healthcare professionals needing quick assessments.
  • Anyone curious about their kidney function based on recent lab results.

While this is not a replacement for professional medical advice, it’s a valuable starting point for discussing kidney health with a doctor.

Frequently Asked Questions (FAQ)

What is eGFR?

eGFR stands for estimated Glomerular Filtration Rate. It’s a calculated number that shows how well your kidneys are working to filter blood.

Which formula should I choose?

The CKD-EPI equation is recommended because it’s more accurate for most people, especially when the GFR is above 60. The MDRD equation is older and tends to underestimate kidney function in healthier individuals.

Is this calculator accurate?

It gives a reliable estimate based on your serum creatinine level. However, actual kidney function can be influenced by other factors. Always consult a healthcare provider for a full assessment.

Can this calculator diagnose kidney disease?

No. A single eGFR result is not enough to diagnose chronic kidney disease. Doctors look at patterns over time and may order more tests.

How This Compares to Other Tools

Just like the TDEE Calculator estimates your calorie burn or the Protein Calculator helps you reach optimal protein levels, the GFR Calculator is all about giving you personalized health data—in this case, your renal filtration rate. Whether you're reviewing your kidney function or managing an existing condition, this calculator simplifies a complex process into clear results.

Health tracking tools like the BAC Calculator for alcohol intake analysis or the Oxfam Care Calculator for philanthropic planning have one thing in common: they provide clarity. The GFR Calculator joins that list by helping users better understand their kidney function with just a few quick inputs.