What this calculator does
An eGFR calculator estimates how well the kidneys are filtering blood, using a routine blood test result for serum creatinine along with age and sex. eGFR stands for estimated glomerular filtration rate, and it is the number that appears on most kidney-function blood test reports, expressed in millilitres per minute per 1.73 square metres of body surface area.
This calculator uses the CKD-EPI 2021 creatinine equation, the current standard formula published by the Chronic Kidney Disease Epidemiology Collaboration. It replaced an earlier 2009 version that included a race adjustment; the 2021 equation removed that term so the same formula now applies to everyone. It is a published, fixed formula rather than a rough rule of thumb, but it still only estimates kidney function from one blood marker, and a doctor interprets the result alongside the rest of a person's health picture.
The formula
The CKD-EPI 2021 equation multiplies a baseline constant by two power terms built from serum creatinine, an age-decay term, and a fixed adjustment for female sex. The two power terms use different sex-specific constants (κ and α) depending on whether serum creatinine sits above or below that constant, which is what lets one equation curve correctly across the whole range of results.
| Term | Meaning |
|---|---|
| eGFR | Estimated glomerular filtration rate, in mL/min/1.73m², the headline kidney-function figure this calculator produces. |
| Scr | Serum creatinine, a waste product measured directly in a blood test, entered here in mg/dL. |
| κ (kappa) and α (alpha) | Fixed sex-specific constants in the CKD-EPI 2021 equation: κ = 0.7 and α = −0.241 for women, κ = 0.9 and α = −0.302 for men. |
| KDIGO stage band | The standard G1 to G5 kidney-function category that a given eGFR result falls into, published by Kidney Disease: Improving Global Outcomes. |
The inputs explained
| Field | What to enter |
|---|---|
| Serum creatinine (mg/dL) | Serum creatinine from a recent blood test, in mg/dL. Most Australian and UK labs report in µmol/L; divide that figure by 88.4 to convert to mg/dL before entering it here. |
| Age (years) | Age in whole years at the time of the blood test. |
| Sex | Sex recorded on the blood test, which sets which pair of equation constants is used. |
When to use it
Reading a kidney-function blood test
A pathology report usually already prints an eGFR figure, calculated the same way. Recomputing it independently is a useful check, and this calculator also shows which KDIGO stage band that number falls into.
Tracking a trend over several tests
A single eGFR result varies a little test to test. Running the same formula on results from different dates, using the serum creatinine from each, shows whether the underlying trend is stable, improving or declining rather than reacting to one reading.
Understanding a stage band on a report
A report that lists a CKD stage rather than a raw number is using the same KDIGO bands shown here, which map a continuous eGFR value onto a small number of standard categories used in kidney care.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How eGFR changes with serum creatinine, at a fixed age and sex
A fixed age of 50 and female sex, across a range of serum creatinine results.
| Serum creatinine | Estimated GFR | KDIGO stage band |
|---|---|---|
| 0.6 mg/dL | 109 mL/min/1.73m² | G1 (normal or high) |
| 0.8 mg/dL | 90 mL/min/1.73m² | G2 (mildly decreased) |
| 1 mg/dL | 69 mL/min/1.73m² | G2 (mildly decreased) |
| 1.2 mg/dL | 55 mL/min/1.73m² | G3a (mildly to moderately decreased) |
| 1.5 mg/dL | 42 mL/min/1.73m² | G3b (moderately to severely decreased) |
| 2 mg/dL | 30 mL/min/1.73m² | G4 (severely decreased) |
How eGFR changes with age, at a fixed serum creatinine
A fixed serum creatinine of 1.0 mg/dL and female sex, across a range of ages.
| Age | Estimated GFR | KDIGO stage band |
|---|---|---|
| 30 years | 78 mL/min/1.73m² | G2 (mildly decreased) |
| 40 years | 73 mL/min/1.73m² | G2 (mildly decreased) |
| 50 years | 69 mL/min/1.73m² | G2 (mildly decreased) |
| 60 years | 64 mL/min/1.73m² | G2 (mildly decreased) |
| 70 years | 61 mL/min/1.73m² | G2 (mildly decreased) |
| 80 years | 57 mL/min/1.73m² | G3a (mildly to moderately decreased) |
Questions
What counts as a normal eGFR?
An eGFR of 90 or above is generally considered normal or high (KDIGO stage G1), though a single result needs to be read alongside other signs of kidney damage, such as protein in the urine, before drawing conclusions. eGFR also declines gradually with age in people with otherwise healthy kidneys.
Why does this calculator not use race as an input?
The CKD-EPI 2021 equation was specifically developed to remove the race coefficient present in the 2009 version, after evidence that race is not a reliable biological proxy for muscle mass or creatinine production. The same formula now applies uniformly.
Can I use a result from a home test kit here?
This calculator will compute a number from whatever serum creatinine value is entered, but home test kits vary widely in accuracy compared with a laboratory assay. A laboratory-reported serum creatinine is the appropriate input for a result you intend to act on.
Does a low eGFR always mean kidney disease?
Not on its own. A single low reading can reflect dehydration, a recent illness, certain medications or muscle mass differences rather than ongoing kidney disease. A doctor typically confirms a low eGFR with a repeat test at least three months apart before diagnosing chronic kidney disease.
For a kidney-function estimate that also factors in body weight, see the creatinine clearance calculator, which uses the older Cockcroft-Gault formula. For a related cardiovascular risk score, see the CHA₂DS₂-VASc calculator.