GFR Calculator (eGFR)
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Results
eGFR (CKD-EPI 2021, creatinine): 69 mL/min/1.73 m², KDIGO category G2 (mildly decreased).
| Category | eGFR | Description |
|---|---|---|
| G1 | 90 or more | Normal or high |
| G2 (this result) | 60–89 | Mildly decreased |
| G3a | 45–59 | Mildly to moderately decreased |
| G3b | 30–44 | Moderately to severely decreased |
| G4 | 15–29 | Severely decreased |
| G5 | Under 15 | Kidney failure |
This does not diagnose kidney disease. A doctor interprets eGFR together with urine tests (albumin) and repeat results over at least three months, and a single low reading can have other causes.
Creatinine-based estimates are less reliable with very high or low muscle mass (bodybuilders, amputations, frailty), in pregnancy, with creatine supplements or very high-protein diets, when kidney function is changing quickly, and at extremes of body size.
This is an estimate, not medical advice. Talk to a doctor about your kidney results.
How to use the GFR calculator
- Enter age and sex. For anyone under 18 the calculator switches to the children's equation and asks for height.
- Enter serum creatinine from the lab report and pick its unit: mg/dL in the US, µmol/L in most other countries.
- If cystatin C was measured, add it (in mg/L) for the combined equation, which is more accurate.
- Read the eGFR and KDIGO category, then take the result to your doctor. Compare with earlier results if you have them; the trend matters most.
eGFR equations
κ = 0.7 (female), 0.9 (male) · α = −0.241 (female), −0.302 (male)
CKD-EPI 2021 creatinine–cystatin C: eGFR = 135 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−0.544 × min(Scys/0.8, 1)^−0.323 × max(Scys/0.8, 1)^−0.778 × 0.9961^age × 0.963 [female]
α = −0.219 (female), −0.144 (male) · Bedside Schwartz (under 18): eGFR = 0.413 × height (cm) ÷ Scr
Scr in mg/dL (µmol/L ÷ 88.4), Scys in mg/L, eGFR in mL/min/1.73 m²
The 2021 equations were developed by the CKD Epidemiology Collaboration (Inker and colleagues, New England Journal of Medicine) from studies of more than 8,000 people, and they leave out the race coefficient that earlier versions used. A joint National Kidney Foundation and American Society of Nephrology task force recommended them for US labs. The "min" and "max" terms switch the exponent depending on whether creatinine is below or above the sex-specific value κ. The bedside Schwartz equation (Schwartz and colleagues, 2009) comes from the Chronic Kidney Disease in Children study.
Worked example
A 50-year-old woman with a creatinine of 1.0 mg/dL: 1.0 ÷ 0.7 = 1.43, which is above 1, so eGFR = 142 × 1.43^−1.200 × 0.9938^50 × 1.012 = 69 mL/min/1.73 m², category G2. A man of the same age and creatinine gets 92 (G1), because κ is 0.9 for men. If her lab reports 88 µmol/L instead, that is 0.995 mg/dL and eGFR 69. With a cystatin C of 1.0 mg/L, the combined equation gives 74. A child 140 cm tall with a creatinine of 0.6 mg/dL has a bedside Schwartz eGFR of 0.413 × 140 ÷ 0.6 = 96.
KDIGO GFR categories
| 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 | Under 15 | Kidney failure |
The categories are from KDIGO, the international kidney guideline group. Chronic kidney disease is defined by kidney damage or an eGFR under 60 lasting more than three months, so one result in G3a, for example, is a reason to talk to a doctor and repeat the test, not a diagnosis.
eGFR by creatinine and age (CKD-EPI 2021)
Generated with the calculator's engine.
| Creatinine (mg/dL) | µmol/L | Women, 30 | Women, 50 | Women, 70 | Men, 30 | Men, 50 | Men, 70 |
|---|---|---|---|---|---|---|---|
| 0.7 | 62 | 119 | 105 | 93 | 127 | 112 | 99 |
| 0.9 | 80 | 88 | 78 | 69 | 118 | 104 | 92 |
| 1.1 | 97 | 69 | 61 | 54 | 93 | 82 | 72 |
| 1.3 | 115 | 57 | 50 | 44 | 76 | 67 | 59 |
| 1.6 | 141 | 44 | 39 | 34 | 59 | 52 | 46 |
| 2 | 177 | 34 | 30 | 26 | 45 | 40 | 35 |
| 3 | 265 | 21 | 18 | 16 | 28 | 25 | 22 |
Why eGFR can be misleading
- Muscle mass. Creatinine is made by muscle, so bodybuilders can look worse than they are, and people with little muscle (frailty, amputation, long illness) can look better.
- Pregnancy. Kidney filtration rises in pregnancy, and these equations were not developed for it.
- Diet and supplements. Creatine supplements, a large meat meal before the test and some medicines can raise creatinine without any change in the kidneys.
- Changing kidney function. During sudden illness, creatinine lags behind, so eGFR is unreliable until levels settle.
- Cystatin C helps. NIDDK notes that combining creatinine and cystatin C is more accurate than either alone, especially near treatment decision points.
This calculator does not diagnose kidney disease; results need a clinician. This is not medical advice; talk to a doctor. Body size for the 1.73 m² scaling is explained in the body surface area calculator.
Sources
- Inker LA, Eneanya ND, Coresh J, et al. New creatinine- and cystatin C-based equations to estimate GFR without race. N Engl J Med 2021;385(19):1737–1749.
- NIDDK, eGFR equations for adults; National Kidney Foundation, CKD-EPI creatinine equation (2021).
- Schwartz GJ, Muñoz A, Schneider MF, et al. New equations to estimate GFR in children with CKD. J Am Soc Nephrol 2009;20(3):629–637.
- KDIGO Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease (2012; 2024 update).
Frequently asked questions
What is eGFR?
eGFR, the estimated glomerular filtration rate, estimates how much blood your kidneys filter each minute, scaled to an average adult body size of 1.73 m². It is calculated from a blood test for creatinine (and sometimes cystatin C) plus age and sex, rather than measured directly.
How is eGFR calculated?
Adult labs in the US now use the CKD-EPI 2021 equation: 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age, × 1.012 for women, where κ is 0.7 for women and 0.9 for men. A 50-year-old man with a creatinine of 1.0 mg/dL has an eGFR of about 92; a 50-year-old woman with the same result, about 69.
What is a normal eGFR?
An eGFR of 90 or more is KDIGO category G1 (normal or high) and 60 to 89 is G2 (mildly decreased). eGFR naturally falls with age, and G1 or G2 on its own, without signs of kidney damage such as albumin in the urine, does not meet the definition of chronic kidney disease. A doctor interprets your results.
Why does the 2021 equation not use race?
Earlier equations multiplied results for Black patients by a fixed factor. Race is a social, not a biological, category, so the CKD-EPI researchers refitted the equations without it in 2021 (Inker et al., NEJM). The National Kidney Foundation and American Society of Nephrology recommend the race-free equations.
When is eGFR less accurate?
Creatinine comes from muscle, so the estimate can mislead with very high or low muscle mass, amputations, frailty, pregnancy, creatine supplements, very high-protein diets and when kidney function is changing quickly. Adding a cystatin C test gives a more accurate estimate in many of these cases.