GFR Calculator
Our GFR calculator determines the glomerular filtration rate by taking into account your serum creatinine, age, ethnicity, and sex. It then displays results from three commonly used estimation equations for easy comparison.
GFR Calculator for Adults
This calculator is for people aged 18 years or older.
GFR Calculator for Children
This calculator is for people aged 18 years or younger.
What is Glomerular filtration rate (GFR)?
Glomerular filtration rate measures how quickly the kidneys filter fluid, serving as an indicator of renal performance. Higher GFR values generally reflect healthier kidneys, while a notable drop suggests impaired function and reduced fluid clearance over time. Normal, body‑surface‑area‑adjusted GFR ranges from 100–130 mL/min/1.73 m² in men and 90–120 mL/min/1.73 m² in women under 40 years. After forty, the rate typically declines gradually with advancing age. See the table below for average estimated GFR values across various age brackets.
Population Mean Estimated GFR
| Age | Mean Estimated GFR (mL/min/1.73 m2) |
| 20-29 | 116 |
| 30-39 | 107 |
| 40-49 | 99 |
| 50-59 | 93 |
| 60-69 | 85 |
| 70+ | 75 |
Chronic Kidney Disease Stages
A GFR exceeding 60 mL/min/1.73 m² is usually sufficient for most individuals and, by itself, does not confirm chronic kidney disease (CKD).¹ However, if your GFR has dropped markedly since a prior test, it may signal early kidney damage. Early detection and treatment improve the chances of avoiding dialysis. The table that follows lists GFR intervals corresponding to CKD stages, which also consider additional clinical factors as indicated.
| Stage | GFR Value (mL/min/1.73 m2) |
| Normal | 90+ or above and no proteinuria |
| CKD1 | 90+ with evidence of kidney damage |
| CKD2 (Mild) | 60 to 89 with evidence of kidney damage |
| CKD3 (Moderate) | 30 to 59 |
| CKD4 (Severe) | 15 to 29 |
| CKD5 Kidney failure | less than 15 |
Measuring GFR
The gold‑standard method for measuring GFR involves tracking the clearance of an external marker such as inulin, which is filtered by the kidneys without being metabolized, secreted, or reabsorbed.² This technique requires continuous IV infusion, multiple blood and urine samples, and precise timing, making it unsuitable for routine practice.³ Consequently, various estimation formulas have been created, most of which rely on creatinine clearance derived from serum creatinine levels. While convenient, creatinine‑based estimates are influenced by muscle mass—greater muscle yields higher serum creatinine for the same filtration rate—and by a small amount of tubular secretion, typically causing a 10–20 % overestimation of true GFR. Despite these drawbacks, creatinine‑based equations remain practical compared with inulin clearance. Below are three widely used serum‑creatinine equations for estimating GFR.
- "Normal GFR," The UK eCKD Guide, The Renal Association.
- Gaspari, F., Perico, N., Remuzzi, G. 1997. "Measurement of glomerular filtration rate." Kidney International Supplements 63: S151-4. PMID 9407445.
- Hsu, C., Bansal, N. 2011. "Measured GFR as 'Gold Standard' – All that Glitters Is Not Gold?" Clinical Journal of the American Society of Nephrology 6(8): 1813-14. Doi:10.2215/CJN.06040611.