GFR Calculator
Calculate your Glomerular Filtration Rate (GFR) to assess kidney function.
A GFR calculator estimates your Glomerular Filtration Rate from a blood creatinine test, providing a key indicator of kidney function and helping detect chronic kidney disease early.
Examples
45-year-old male, creatinine 1.0
Frequently Asked Questions
What does GFR measure?
When should I be concerned about my GFR?
Quick Tips
- •Always discuss your eGFR results with your doctor, who can interpret them alongside other lab values and your medical history.
- •Stay well-hydrated before your blood test, as dehydration can temporarily affect creatinine levels.
- •If your eGFR is below 60, ask about follow-up testing to determine whether the change is acute or chronic.
A GFR calculator estimates your Glomerular Filtration Rate from a blood creatinine test, providing a key indicator of kidney function and helping detect chronic kidney disease early.
How to Use This Calculator
Enter your serum creatinine level (from a blood test), age, sex, and race. The calculator estimates your Glomerular Filtration Rate (eGFR) using the CKD-EPI 2021 equation and classifies your kidney function stage.
Understanding the Formula
CKD-EPI 2021: eGFR = 142 x min(Scr/kappa, 1)^alpha x max(Scr/kappa, 1)^(-1.200) x 0.9938^age x (1.012 if female). Kappa = 0.9 (M) or 0.7 (F). Alpha = -0.302 (M) or -0.241 (F).
Examples
45-year-old male, creatinine 1.0
eGFR = 142 x min(1.0/0.9, 1)^(-0.302) x max(1.0/0.9, 1)^(-1.200) x 0.9938^45 = approximately 92 mL/min/1.73m² (Stage G1, normal).
Frequently Asked Questions
What does GFR measure?
Glomerular Filtration Rate measures how well your kidneys filter waste from your blood, expressed in mL/min/1.73m². A GFR of 90+ is generally considered normal. Lower values indicate reduced kidney function.
When should I be concerned about my GFR?
A single low GFR reading does not necessarily mean kidney disease. GFR below 60 for 3 or more months is considered chronic kidney disease. Always discuss results with your doctor, who will consider the full clinical picture.
Assumptions & Limitations
- The CKD-EPI 2021 equation is based on serum creatinine, which can be affected by muscle mass, diet, and medications.
- A single eGFR value is not diagnostic — kidney disease requires persistently low readings over at least 3 months.
- The 2021 equation removed the race coefficient, but results may still vary across populations.