Calculators

GFR Calculator

mg/dL
40 years
Gender
eGFR97.6 mL/min
StageStage 1
DescriptionNormal kidney function

Estimated glomerular filtration rate (eGFR) gauges how well your kidneys filter waste from the blood, and it is the key number behind staging chronic kidney disease. This calculator applies the 2021 CKD-EPI creatinine equation, the current race-free standard, using your serum creatinine, age, and sex to produce an eGFR in mL/min/1.73 m² and the matching CKD stage. It is an educational estimate, not a substitute for clinical testing.

Formula

eGFR = 142 × min(Scr/κ,1)^α × max(Scr/κ,1)^−1.200 × 0.9938^age × (1.012 if female)

Scr
Serum creatinine in mg/dL
κ
0.7 for females, 0.9 for males
α
−0.241 for females, −0.302 for males
age
Age in years (0.9938 raised to age applies the decline with age)

How it works

  1. Enter your serum creatinine in mg/dL, your age in years, and your sex.
  2. The 2021 CKD-EPI equation scales creatinine by a sex-specific factor (κ = 0.7 for women, 0.9 for men), applies low- and high-creatinine exponents, and includes an age decay term plus a female adjustment.
  3. The resulting eGFR is mapped to a CKD stage — Stage 1 (≥90), 2 (60–89), 3a (45–59), 3b (30–44), 4 (15–29), or 5 (under 15) — with a plain-language description of kidney function.

Worked examples

A 40-year-old man with a serum creatinine of 1.0 mg/dL.

  1. Scr/κ = 1.0 / 0.9 = 1.111; min term = min(1.111,1)^−0.302 = 1; max term = 1.111^−1.200 ≈ 0.879.
  2. Age term = 0.9938^40 ≈ 0.7807; male factor = 1.0.
  3. eGFR = 142 × 1 × 0.879 × 0.7807 ≈ 97.6.

eGFR ≈ 97.6 mL/min → Stage 1, normal kidney function.

A 55-year-old woman with a serum creatinine of 1.4 mg/dL.

  1. Scr/κ = 1.4 / 0.7 = 2.0; max term = 2.0^−1.200 ≈ 0.435; min term = 1.
  2. Age term = 0.9938^55 ≈ 0.7104; female factor = 1.012.
  3. eGFR = 142 × 1 × 0.435 × 0.7104 × 1.012 ≈ 44.4.

eGFR ≈ 44.4 mL/min → Stage 3b, moderate to severe decrease.

Frequently asked questions

What is a normal eGFR?
An eGFR of 90 or above with no other signs of kidney damage is generally considered normal (Stage 1). Values decline naturally with age, and a result below 60 sustained for three months suggests chronic kidney disease.
Why does this use the 2021 CKD-EPI equation?
The 2021 CKD-EPI creatinine equation removed the race coefficient used in older formulas, making estimates more equitable. It is now the recommended standard for reporting eGFR from serum creatinine in adults.
How is serum creatinine related to kidney function?
Creatinine is a waste product cleared by the kidneys. As filtering capacity falls, creatinine builds up in the blood, so a higher serum creatinine generally produces a lower estimated GFR.
Can I rely on this instead of a doctor's test?
No. eGFR estimates can be affected by muscle mass, diet, and hydration, and CKD staging requires clinical context and repeat testing. Discuss any concerning result with a healthcare professional.

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