CalcGFR Calculator (CKD-EPI 2021)
Last updated: 2026-09-30
How to Use This Calculator
This GFR calculator uses the race-free CKD-EPI 2021 creatinine equation to estimate glomerular filtration rate (eGFR) from serum creatinine, age, and sex. To use it, simply enter your serum creatinine value, select the unit (mg/dL or µmol/L), input your age, and select your sex. The calculator will automatically compute your eGFR in mL/min/1.73m², display the corresponding CKD stage, and show your creatinine in both conventional and SI units for reference.
Formula and Methodology
The CKD-EPI 2021 equation is: eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^-1.200 × 0.9938^Age × 1.012 [if female]. Here, Scr is serum creatinine in mg/dL, κ is 0.7 for females and 0.9 for males, and α is -0.241 for females and -0.302 for males. If the input creatinine is in µmol/L, it is first divided by 88.4 to convert to mg/dL. This equation was developed to provide a more accurate and equitable estimate of kidney function without using race as a variable.
Practical Examples
For example, a 50-year-old male with a serum creatinine of 1.0 mg/dL: κ = 0.9, Scr/κ = 1.11, min(1.11,1) = 1, max(1.11,1) = 1.11. eGFR = 142 × 1^-0.302 × 1.11^-1.200 × 0.9938^50. This yields approximately 87 mL/min/1.73m², indicating CKD stage G2. A 65-year-old female with serum creatinine of 132 µmol/L (which is 132/88.4 = 1.49 mg/dL): κ = 0.7, Scr/κ = 2.13, min = 1, max = 2.13. eGFR = 142 × 1^-0.241 × 2.13^-1.200 × 0.9938^65 × 1.012 ≈ 42 mL/min/1.73m², indicating stage G3a.
Tips and Best Practices
Always use a stable serum creatinine value, as eGFR can fluctuate with acute illness or dehydration. For clinical decision-making, trend eGFR over time rather than relying on a single measurement. Confirm chronicity by repeating tests after at least 3 months. Remember that eGFR is indexed to body surface area (1.73 m²) and may not be accurate in extremes of body size. Use the calculator as a screening aid, and consult a healthcare professional for diagnosis and management.
Related Calculators
- Advanced Age Calculator
- Asphalt Tonnage Calculator
- Backsplash Tile Calculator
- Baseboard Calculator
- Brazilian Drywall Stud Spacing Calculator
FAQ
What is the CKD-EPI 2021 equation?
The CKD-EPI 2021 creatinine equation is a race-free formula developed by the Chronic Kidney Disease Epidemiology Collaboration to estimate glomerular filtration rate (eGFR) from serum creatinine, age, and sex. It is recommended by the National Kidney Foundation and the American Society of Nephrology.
Why is race no longer used in the CKD-EPI 2021 equation?
The 2021 equation removed the race coefficient because race is a social construct, not a biological one. The previous inclusion of race could lead to underestimation of kidney disease severity in Black individuals and contribute to health disparities. The new equation provides more equitable estimates.
What do the CKD stages mean?
CKD stages are based on eGFR: G1 (≥90) indicates normal or high kidney function; G2 (60–89) indicates mildly decreased function; G3a (45–59) and G3b (30–44) indicate moderate decreases; G4 (15–29) indicates severely decreased function; and G5 (<15) indicates kidney failure. Stages are also influenced by other markers of kidney damage.
Can I use this calculator for children?
No, the CKD-EPI 2021 equation is validated for adults (≥18 years). For children and adolescents, the CKiD U25 equation or Schwartz formula is recommended.
How accurate is the eGFR calculation?
The CKD-EPI 2021 equation is generally accurate for estimating GFR in adults, but it can be less accurate in certain populations such as very muscular individuals, those with extreme body sizes, or pregnant women. It is a screening tool, not a substitute for direct GFR measurement.