About this GFR Calculator
Glomerular Filtration Rate (GFR) is the best test to measure your level of kidney function and determine your stage of kidney disease. Since direct GFR measurement is difficult, doctors calculate 'eGFR' (estimated GFR) based on a blood test for creatinine.
Who this calculator is for
- Adults reviewing lab work who want to understand an eGFR result.
- People monitoring kidney function trends with clinician guidance.
- Anyone learning how creatinine, age, and sex affect eGFR estimates.
When to use it
- Use this calculator after a creatinine blood test to estimate kidney filtration.
- Use it when comparing results over time for stable chronic monitoring.
- Use it to better understand the stage labels often shown with lab reports.
How to use this calculator
- Enter the Serum Creatinine level from your lab report.
- Enter your Age.
- Select your Gender.
- The tool calculates eGFR and identifies the CKD Stage.
Key assumptions
- The estimate uses the CKD-EPI 2021 creatinine equation for stable adults.
- It assumes serum creatinine is from a routine steady-state lab value rather than an acute medical event.
- eGFR is an estimate and may be less reliable at extremes of muscle mass, diet, or body size.
Accuracy and testing
Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.
How this calculator works
This calculator uses the CKD-EPI 2021 Equation, which is currently recommended by the National Kidney Foundation. It accounts for age, sex, and serum creatinine. Unlike older formulas (MDRD), the 2021 version removed the race coefficient to reduce bias in clinical care.
Inputs explained
Serum Creatinine
A waste product in your blood that comes from muscle activity. Healthy kidneys filter it out. High levels suggest kidney issues.
Age
Kidney function naturally declines slightly with age.
Understanding your results
eGFR represents the flow rate of filtered fluid through the kidney.
* > 90: Normal
* 60-89: Mildly decreased
* 30-59: Moderate to severe loss (CKD Stage 3)
* 15-29: Severe loss (CKD Stage 4)
* < 15: Kidney Failure (Stage 5)
Example scenarios
Healthy Adult
Male, Age 30, Creatinine 0.9. eGFR = 113 (Normal).
Possible CKD
Female, Age 60, Creatinine 1.4. eGFR = 44 (Stage 3b).
Key Features
- CKD-EPI 2021 Standard
- Race-Free Logic
- Staging Interpretation
Things to Keep in Mind
Not for acute kidney injury (AKI). Only valid for stable adults (18+).
Tips & Best Practices
- eGFR is an estimate. It can be inaccurate in people with extremes of muscle mass (bodybuilders or amputees) because creatinine comes from muscle.
- Drink water before a blood test; dehydration can temporarily raise creatinine levels and lower your eGFR result.
Glossary of Terms
- CKD
- Chronic Kidney Disease. Defined as having kidney abnormality or eGFR < 60 for more than 3 months.
- Creatinine
- A chemical waste molecule generated from muscle metabolism.