GFR Calculator

1. Find your serum creatinine value. This comes from a blood test ordered by your doctor, typically as part of a basic metabolic panel (BMP) or comprehensive metabolic panel (CMP). The value is reported in mg/dL.
2. Enter your age. The CKD-EPI formula uses age because kidney filtration naturally declines with age. A creatinine of 1.2 mg/dL means something different for a 25-year-old than for a 75-year-old.
3. Select your sex. Biological sex affects muscle mass and therefore creatinine production. Women tend to produce less creatinine than men at the same weight, so the formula uses different thresholds.
4. Read your eGFR result and CKD stage. An eGFR of 60 or above is generally considered normal or mildly reduced. Below 60 for three or more months indicates chronic kidney disease.

This calculator uses the CKD-EPI Creatinine 2021 equation, which replaced the 2009 version to eliminate the race coefficient. It is the current standard recommended by KDIGO guidelines.

For females (Scr in mg/dL):

If Scr ≤ 0.7:
eGFR = 142 × (Scr / 0.7)^-0.241 × (0.9938)^Age × 1.012

If Scr > 0.7:
eGFR = 142 × (Scr / 0.7)^-1.200 × (0.9938)^Age × 1.012

For males (Scr in mg/dL):

If Scr ≤ 0.9:
eGFR = 142 × (Scr / 0.9)^-0.302 × (0.9938)^Age

If Scr > 0.9:
eGFR = 142 × (Scr / 0.9)^-1.200 × (0.9938)^Age

Example (male, age 50, creatinine 1.2 mg/dL):

Scr > 0.9, so use second equation:
eGFR = 142 × (1.2 / 0.9)^-1.200 × (0.9938)^50
     = 142 × 1.333^-1.200 × 0.9938^50
     = 142 × 0.739 × 0.732
     = 76.8 mL/min/1.73m² → Stage G2

The 0.9938^Age factor captures the natural age-related decline in GFR of approximately 0.62% per year after age 40.