eGFR Calculator
See the estimated glomerular filtration rate the race-free CKD-EPI 2021 equation gives for a creatinine result, age and sex. An estimate, not a diagnosis.
Result
Enter serum creatinine, mg/dl, age and sex used by the equation to see the result.
https://calcgallery.com/health-risk/gfr-calculator/
How to use the eGFR Calculator
- Find the serum creatinine result on your lab report and the unit printed beside it.
- Choose that unit, mg/dL or µmol/L, then enter the number exactly as reported.
- Enter your age in whole years and choose the sex equation.
- Read the estimate and the category it falls in, and take both to the clinician who ordered the test.
Read this first
This is an estimate, not a diagnosis, and not medical advice. It applies a published equation to the numbers you enter. It cannot tell you whether your kidneys are healthy, whether anything needs to change, or what to do next. Discuss your results with a clinician.
A single eGFR does not diagnose chronic kidney disease. Under the KDIGO 2012 guideline, kidney disease is defined by abnormalities of kidney structure or function that are present for more than three months, and the GFR figure is read alongside albuminuria and the rest of the clinical picture. One number from one blood test is not that.
What eGFR estimates
Glomerular filtration rate is how much blood the kidneys filter each minute. It cannot practically be measured in routine care, so it is estimated from the level of creatinine in the blood. Creatinine is a waste product of muscle that the kidneys clear, so when filtration falls, creatinine tends to rise.
The result is in mL/min/1.73 m²: millilitres a minute, scaled to a standard body surface area of 1.73 square metres. The scaling lets results be compared between people of different sizes. It also means the figure is not your own filtration in millilitres a minute; a larger or smaller body filters more or less than the normalised number says. The body surface area calculator, linked below, shows what your own surface area is.
How it is calculated
The 2021 CKD-EPI creatinine equation (Inker and colleagues, New England Journal of Medicine, 2021):
eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age × 1.012 if female| Equation | κ | α | Extra factor |
|---|---|---|---|
| Female | 0.7 | −0.241 | × 1.012 |
| Male | 0.9 | −0.302 | none |
Scr is serum creatinine in mg/dL, standardised to the IDMS reference method, as laboratories now report it. Age is in years. The equation has a bend at Scr = κ: below it creatinine changes the result gently, through α, and above it steeply, through −1.200. Those coefficients, and the example tests the equation’s authors publish for anyone programming it, come from the CKD-EPI research group, and the same equation is reproduced by NIDDK and the National Kidney Foundation.
Creatinine units. Much of the world reports creatinine in µmol/L. The equation takes mg/dL, so a µmol/L result is divided by 88.4 first, the factor KDIGO and NIDDK give. The same creatinine is about 88 times larger in µmol/L, so a unit slip is the easiest serious error to make here. That is why the page asks for the unit before the number and gives each unit its own field with its own limits: a µmol/L value typed into the mg/dL field is refused rather than turned into a plausible-looking answer.
The estimate is shown as a whole number, as KDIGO recommends laboratories report it, and the category is read from that whole number.
Why the 2021 equation has no race term
The 2009 CKD-EPI equation, which many online calculators and some laboratories still use, included a multiplier for people identified as Black. The 2021 equation was refitted without it, using age and sex only, and is what the NKF and ASN task force recommended laboratories adopt.
The two do not give the same answer. According to the CKD-EPI group’s implementation guidance, for people previously identified as Black the 2021 result is on average lower than the 2009 one, and for everyone else it is on average higher; the size of the difference depends on age, sex and the level of GFR. A calculator using the 2009 equation will therefore disagree with this one, and results from the two should not be compared as though they were a trend.
KDIGO GFR categories
The KDIGO 2012 guideline groups GFR into six categories. The page shows which one a number falls in, because that is the standard vocabulary your clinician will use. It is a label for the number, not a diagnosis.
| Category | GFR, mL/min/1.73 m² | KDIGO term |
|---|---|---|
| G1 | 90 or more | Normal or high |
| G2 | 60 to 89 | Mildly decreased |
| G3a | 45 to 59 | Mildly to moderately decreased |
| G3b | 30 to 44 | Moderately to severely decreased |
| G4 | 15 to 29 | Severely decreased |
| G5 | Below 15 | Kidney failure |
KDIGO notes that without other evidence of kidney damage, neither G1 nor G2 meets the criteria for chronic kidney disease. “Mildly decreased” in G2 is relative to a young adult’s level, and the equation itself lowers the estimate a little with every year of age.
When the estimate is less reliable
The equation assumes creatinine is steady and is produced at the rate typical of the people it was fitted on. KDIGO 2012 (Table 11) and the National Kidney Foundation list situations where that is not true and an estimate from creatinine can be wrong:
- Acute kidney injury or any other time kidney function is changing quickly: the equation needs a steady state.
- Pregnancy.
- Extremes of muscle mass or body size: amputation, paralysis, muscle-wasting conditions, very high muscle mass or very small or large bodies.
- Diet: a high-protein diet, creatine supplements, cooked meat eaten shortly before the test, or poor nutrition.
- Some medicines, such as trimethoprim, cimetidine and fenofibrate, which reduce the kidneys’ secretion of creatinine and raise it without changing filtration.
- Liver cirrhosis, nephrotic syndrome, a past organ transplant, and dialysis.
- Higher GFR generally, where the estimate is less precise, and older age.
In several of these a clinician may confirm the estimate with a different test, such as cystatin C or a measured GFR. This page does not implement the cystatin C equations.
Before you compare numbers
Use the unit on the report. If the creatinine has no decimal point and is in the tens or hundreds, it is almost certainly µmol/L.
Compare like with like. A change in equation can move eGFR by several points with no change in the kidneys. Numbers from different equations, or from different laboratories, are not a trend.
One result is one result. Creatinine can move between tests for reasons that have nothing to do with the kidneys, a meat meal the evening before among them. Kidney disease is judged on results that persist for more than three months, not on a single figure.
With your numbers
- Female equation: κ = 0.7, α = −0.241, and × 1.012
- Creatinine ÷ κ = 1.571, which is above the knot at 1
- eGFR = 142 × min(1.571, 1)^α × max(1.571, 1)^−1.200 × 0.9938^55 = 59 mL/min/1.73 m², in category G3a
Quick reference
An estimate from one creatinine result. What it means for you is a question for the clinician who ordered the test.
| Example | Estimated GFR, mL/min/1.73 m² |
|---|---|
| 0.7 mg/dL, 30, female | 119 |
| 0.9 mg/dL, 40, male | 111 |
| 1.0 mg/dL, 60, male | 86 |
| 1.1 mg/dL, 55, female | 59 |
| 1.6 mg/dL, 70, female | 34 |
| 2.5 mg/dL, 65, male | 28 |
| 62 µmol/L, 30, female | 119 |
| 80 µmol/L, 40, male | 110 |
| 97 µmol/L, 55, female | 60 |
| 150 µmol/L, 70, male | 43 |
Where the numbers come from
The fixed figures this calculator relies on, and the published source each one was checked against. How the calculators are built and checked
2 sources
KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of CKD, Kidney Int Suppl 3(1), 2013, "Conversion factors of metric units to SI units", p. xi (creatinine, serum: mg/dl × 88.4 = µmol/l). The same factor is given by NIDDK, "eGFR Equations for Adults" (divide µmol/L by 88.4), niddk.nih.gov, and by the CKD-EPI group, "Implementation of the 2021 CKD-EPI GFR equations", Tufts Medicine, 8 Dec 2021.
Used for
- Serum creatinine in mg/dL times this gives µmol/L; the equation takes mg/dL, so a µmol/L entry is divided by it.
KDIGO 2012 CKD guideline, Kidney Int Suppl 3(1), 2013, Table 5 "GFR categories in CKD", p. 27.
Used for
- Lower bound of KDIGO GFR category G1, normal or high.
- Lower bound of KDIGO GFR category G2, mildly decreased (60 to 89).
- Lower bound of KDIGO GFR category G3a, mildly to moderately decreased (45 to 59).
- Lower bound of KDIGO GFR category G3b, moderately to severely decreased (30 to 44).
- Lower bound of KDIGO GFR category G4, severely decreased (15 to 29). Below it is G5.
Common questions about the eGFR Calculator
- What does my number mean?
- Ask the clinician who ordered the test. An eGFR is read together with your other results, your history, any medicines you take and, usually, a urine albumin test, and a single value on its own does not tell anyone whether you have kidney disease. This page can show you what the equation does with one creatinine result. It cannot tell you what that result means for you, and it does not try.
- Why is this different from the number on my lab report?
- Three common reasons. The laboratory may use a different equation: many reports still use the 2009 CKD-EPI equation, and some use other equations entirely. The laboratory may use your exact age from your date of birth, where this page takes whole years. And some laboratories print a high result as "greater than 60" or "greater than 90" rather than as a number. If the report and this page disagree, the report is the one your clinician is working from.
- What is the difference between eGFR and creatinine clearance?
- Creatinine clearance is measured, usually from a timed urine collection alongside a blood sample, or is estimated with a different equation such as Cockcroft-Gault, which uses body weight and gives an answer in mL/min without the 1.73 m² adjustment. eGFR comes from a blood creatinine result, age and sex alone and is scaled to a standard body size. The two are not interchangeable, and medicine dosing guidance often says which one it means. This page gives eGFR only.
- Why did the race coefficient go?
- The 2009 equation multiplied the result by a fixed factor for people identified as Black, which meant a clinician had to assign a race to a patient before a kidney result could be calculated. In 2021 a joint task force of the US National Kidney Foundation and the American Society of Nephrology concluded that race should not be included in GFR estimating equations, and recommended the new CKD-EPI equation, refitted on age and sex alone, for immediate use by laboratories. This page implements only that 2021 equation.
- Can I use this for a child or during pregnancy?
- No. The equation applies from age 18, so the page refuses younger ages; children have their own equations, which this page does not implement. Pregnancy changes kidney filtration and creatinine, and the National Kidney Foundation lists it among the situations where an eGFR may not be accurate.