This calculator gives general estimates for information only. It does not replace advice from your doctor, pharmacist or another qualified health professional.
What eGFR measures
The kidneys filter waste from the blood through millions of tiny filters, the glomeruli. The glomerular filtration rate (GFR) is the volume of blood they clean each minute. Measuring it directly is complicated, so labs estimate it (eGFR) from blood creatinine, a waste product of muscle, together with age and sex. It is expressed in mL/min per 1.73 m², the body surface area of an average adult. A healthy young adult is around 100 to 120.
The CKD-EPI 2021 equation
Since 2021, US labs use a version without the race coefficient of earlier equations:
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age × 1.012 (if female)
with Scr the creatinine in mg/dL, κ = 0.7 for women and 0.9 for men, and α = −0.241 for women and −0.302 for men.
The calculator also shows the older Cockcroft-Gault creatinine clearance, (140 − age) × weight (kg) ÷ (72 × Scr), × 0.85 for women. Some drug labels still use it to adjust doses.
Worked example: a 50-year-old man, creatinine 1.0 mg/dL, 180 lb
- Scr/κ = 1.0 ÷ 0.9 = 1.11, so the first factor is 1 and the second is 1.11^−1.2 = 0.881.
- Age factor: 0.9938^50 = 0.733.
- eGFR = 142 × 0.881 × 0.733 = 92 mL/min/1.73 m², stage G1.
- Cockcroft-Gault: (140 − 50) × 81.6 ÷ 72 = 102 mL/min.
Stages of chronic kidney disease
| Stage | eGFR | Meaning |
|---|---|---|
| G1 | 90 or more | normal, kidney disease only if there are other signs |
| 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 diagnosed when eGFR stays below 60 for more than three months, or when there is kidney damage such as albumin in the urine.
eGFR by age (same creatinine)
| Age | eGFR |
|---|---|
| 30 | 104 |
| 50 | 92 |
| 70 | 81 |
| 80 | 76 |
Limits
Creatinine depends on muscle mass. eGFR overestimates kidney function in people with little muscle (older adults, amputees) and underestimates it in very muscular people or after a big steak or creatine supplements. It is also unreliable in pregnancy, children and acute illness. Your doctor may confirm it with a cystatin C test.