GFR Calculator Kidney Function Test
GFR Calculator
Adult Parameters
Normal range: 0.6-1.2 mg/dL (varies by lab)
Used for formula adjustments based on population studies
GFR (Glomerular Filtration Rate) measures how well your kidneys filter waste from the blood. Estimated GFR (eGFR) is calculated from a simple blood creatinine test combined with age, sex, and race. This calculator computes eGFR using the CKD-EPI 2021 equation and interprets the result according to the CKD staging system.
eGFR Calculation
The CKD-EPI 2021 equation (which replaced the 2009 race-based equation) uses serum creatinine, age, and sex to estimate kidney filtration rate without a separate race variable.
CKD-EPI 2021 (simplified form): eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^-1.200 × 0.9938^Age × (1.012 if female) κ: 0.7 (females), 0.9 (males) α: -0.241 (females), -0.302 (males) Scr = serum creatinine (mg/dL)
GFR is expressed in mL/min/1.73m². A young healthy adult has eGFR > 100.
CKD Staging by eGFR
| Stage | eGFR (mL/min/1.73m²) | Description |
|---|---|---|
| G1 | >= 90 | Normal or high (with kidney damage markers) |
| 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 | < 15 | Kidney failure (ESRD) |
Frequently Asked Questions
What is a normal GFR level?⌄
A GFR of 60 or above is generally considered in the normal or near-normal range for most adults. GFR naturally declines with age (about 1 mL/min/yr after age 40). An eGFR below 60 for more than 3 months indicates chronic kidney disease (CKD). Always interpret GFR in conjunction with other kidney function tests and your doctor's assessment.
Can GFR improve?⌄
Mild to moderate CKD can sometimes be slowed or stabilized but rarely reverses significantly. Improving blood pressure control, blood sugar management in diabetes, reducing protein intake, and treating underlying causes can slow decline. Acute kidney injury (AKI) often fully recovers. Working with a nephrologist is important for managing CKD progression.
What causes GFR to decrease?⌄
The most common causes of reduced GFR are diabetes (diabetic nephropathy), hypertension, chronic glomerulonephritis, polycystic kidney disease, and repeated episodes of acute kidney injury. Some medications (NSAIDs, contrast dyes) can also impair kidney function temporarily. Regular monitoring is key for anyone with diabetes, hypertension, or family history of kidney disease.
What is the difference between eGFR and creatinine?⌄
Serum creatinine is the raw blood test result. eGFR is derived from creatinine plus age and sex to give a standardized estimate of kidney filtration rate. Creatinine alone can be misleading: a very muscular person has higher creatinine naturally, making their kidneys seem worse than they are. eGFR corrects for this by accounting for the expected creatinine production for a person of that age and sex.