GFR Calculator
Estimate your glomerular filtration rate (eGFR) from a blood creatinine result, your age and sex using the 2021 CKD-EPI equation that labs now use. You get the eGFR, the kidney function category G1–G5 and the formula with your numbers. For information only.
From your blood test report.
How to use the GFR Calculator
- Find your serum creatinine on your blood test report and choose its unit (mg/dL or µmol/L).
- Enter your age (18 or older) and select your sex.
- Press Calculate eGFR to see the estimated GFR in mL/min/1.73 m² and its G category.
- Check the steps and table to see how the equation works and how eGFR changes with creatinine.
- Discuss the result with your doctor, especially if it is below 60 or has changed.
The CKD-EPI 2021 eGFR equation
The calculator uses the race-free 2021 CKD-EPI creatinine equation (Inker et al., New England Journal of Medicine, 2021):
eGFR = 142 × min(Scr/κ, 1)α × max(Scr/κ, 1)−1.200 × 0.9938Age × 1.012 [if female]
- Scr = serum creatinine in mg/dL (µmol/L ÷ 88.4)
- κ = 0.7 for females, 0.9 for males
- α = −0.241 for females, −0.302 for males
- Age in years (adults 18+)
Example: a 50-year-old woman with creatinine 0.8 mg/dL has Scr/κ = 1.143, so eGFR = 142 × 1 × 1.143−1.2 × 0.993850 × 1.012 ≈ 142 × 0.852 × 0.733 × 1.012 ≈ 90 mL/min/1.73 m².
GFR categories (KDIGO)
| Category | eGFR (mL/min/1.73 m²) | Description |
|---|---|---|
| G1 | 90 or more | Normal or high |
| G2 | 60–89 | Mildly decreased |
| G3a | 45–59 | Mildly to moderately decreased |
| G3b | 30–44 | Moderately to severely decreased |
| G4 | 15–29 | Severely decreased |
| G5 | Below 15 | Kidney failure |
Chronic kidney disease is defined by kidney damage or an eGFR below 60 that lasts longer than three months. Doctors also look at the urine albumin-to-creatinine ratio (A1–A3) alongside the G category.
This page is for education only and is not a substitute for medical advice.
Frequently asked questions
What is eGFR?
eGFR (estimated glomerular filtration rate) estimates how many milliliters of blood your kidneys filter per minute, scaled to a standard body surface area of 1.73 m². It is calculated from a blood creatinine level, age and sex instead of being measured directly.
Which formula does this calculator use?
It uses the 2021 CKD-EPI creatinine equation without a race coefficient: eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age × 1.012 (if female), with κ = 0.7 and α = −0.241 for females and κ = 0.9 and α = −0.302 for males. The NKF and ASN recommended it in 2021.
What is a normal eGFR?
An eGFR of 90 or higher is normal (category G1), and 60–89 (G2) is common in older adults. Below 60 for more than three months is classed as chronic kidney disease (G3a and lower). eGFR naturally declines slowly with age.
What are the CKD stages by eGFR?
KDIGO categories are G1 ≥90, G2 60–89, G3a 45–59, G3b 30–44, G4 15–29 and G5 below 15 mL/min/1.73 m². G1 and G2 count as CKD only if there are other markers of kidney damage, such as albumin in the urine.
How do I convert creatinine from µmol/L to mg/dL?
Divide µmol/L by 88.4. For example, 88 µmol/L ÷ 88.4 ≈ 1.0 mg/dL. The calculator does this for you when you choose µmol/L.
Why might my eGFR be inaccurate?
Creatinine depends on muscle mass, so eGFR can be misleading for very muscular people, amputees, people with very low muscle mass, during pregnancy, after a large meat meal or with acute illness. A cystatin C test or measured GFR may be used in those cases.
Can I use this for medication dosing or diagnosis?
No. This calculator is for general information only. Diagnosis and any treatment decisions must be made by a qualified health professional.