About the GFR Calculator
Estimated glomerular filtration rate indicates how well your kidneys are filtering waste from your blood. It is the primary measure used to stage chronic kidney disease, calculated from a serum creatinine blood test along with age and sex.
The formula
CKD-EPI: eGFR = 142 · min(Scr/κ,1)^α · max(Scr/κ,1)^−1.2 · 0.9938^age · fScr is serum creatinine in mg/dL, κ is 0.7 for females and 0.9 for males, α is −0.241 for females and −0.302 for males, and f is 1.012 for females. Results are in mL/min/1.73m².
How to use this calculator
- 1Enter your Serum Creatinine (mg/dL). The field starts at
1, which you can overwrite. - 2Enter your Age (years). The field starts at
45, which you can overwrite. - 3Enter your Female? (1=Yes, 0=No). The field starts at
0, which you can overwrite. - 4Read the result straight away — it recalculates as you type, so there is no button to press. Use Share to copy a link that reopens the page with your exact numbers filled in.
Worked example
| Input | Value |
|---|---|
| Serum Creatinine (mg/dL) | 1 |
| Age (years) | 45 |
| Female? (1=Yes, 0=No) | 0 |
Result
eGFR: 94.6 mL/min/1.73m²
CKD Stage: G1 – Normal or High
(Normal > 60 mL/min/1.73m²)
Those are the values the page loads with, so you can reproduce this result yourself and then change one field at a time to see what drives the outcome.
Understanding your result
Creatinine is a waste product of muscle metabolism that healthy kidneys clear efficiently. As filtration declines, creatinine accumulates, so a rising level indicates falling kidney function. Because production depends on muscle mass, the equation adjusts for age and sex to convert a concentration into a filtration estimate.
The staging matters clinically. Above 90 is normal, 60 to 89 mildly reduced, 45 to 59 and 30 to 44 moderately reduced, 15 to 29 severely reduced, and below 15 is kidney failure. The 2021 CKD-EPI equation removed the race coefficient present in earlier versions, which had been shown to overestimate function in Black patients and delay referral for treatment.
Things worth knowing
- A single reading is not a diagnosis. Chronic kidney disease requires reduced eGFR persisting over three months.
- Very high muscle mass, creatine supplementation, or a large meat meal can raise creatinine and understate eGFR.
- Cystatin C is an alternative marker less affected by muscle mass, useful when creatinine-based estimates seem inconsistent.
- Urine albumin-to-creatinine ratio is measured alongside eGFR, since protein in the urine indicates damage independently.
- Many drug doses require adjustment at reduced eGFR. Tell any prescriber about known kidney impairment.
Frequently asked questions
What is a normal eGFR?+
Above 90 mL/min/1.73m² is normal for a healthy adult. Values decline naturally with age, so 70 in an 80-year-old may be unremarkable while the same figure at 30 warrants investigation.
What does a low eGFR mean?+
Reduced kidney filtration. Below 60 sustained over three months indicates chronic kidney disease, and below 15 indicates kidney failure requiring dialysis or transplant. A single low reading needs repeating before conclusions are drawn.
Can eGFR improve?+
Yes in acute kidney injury, where function often recovers once the cause is treated. Chronic decline is usually not reversible, but progression can be slowed substantially through blood pressure control, glucose management, and medication.
Why was the race coefficient removed?+
Because it overestimated kidney function in Black patients, delaying referrals for specialist care and transplant listing. The 2021 CKD-EPI equation removed it and is now the recommended standard.