This calculator estimates eGFR from age, sex, and serum creatinine using the CKD-EPI 2021 creatinine equation without a race coefficient. It returns a number in mL/min/1.73 m². It does not tell you whether the result is normal, does not stage kidney disease, and does not replace the value or range on your report.
What this calculator does
eGFR is an estimate of the glomerular filtration rate, the rate at which the kidneys filter waste from the blood. The CKD-EPI 2021 creatinine equation combines serum creatinine, age, and sex into a single estimate. It is the version that removed the race coefficient, and it is the version this calculator implements.
The result is an estimate, not a measurement. A laboratory may report a different eGFR from the same creatinine value because it uses a different equation, a different calibration, or an additional marker such as cystatin C. The value on your report is the value your clinician is working with.
The equation
The CKD-EPI 2021 creatinine equation, without a race coefficient, as published by Inker and colleagues in the New England Journal of Medicine in 2021:
eGFR = 142 × min(Scr / κ, 1)^α × max(Scr / κ, 1)^-1.2 × 0.9938^age × sex factor| Variable | Meaning |
|---|---|
| Scr | Serum creatinine in mg/dL. |
| κ (kappa) | 0.7 for female, 0.9 for male. |
| α (alpha) | -0.241 for female, -0.302 for male. |
| Age | Age in years at the time of the sample. |
| Sex factor | 1.012 for female, 1 for male. |
| min and max | The smaller and larger of Scr / κ and 1. |
| Result | eGFR in mL/min/1.73 m², normalized to a body surface area of 1.73 square metres. |
How to use it
- Enter the age at the time the sample was collected, not the age today if the report is old.
- Select the sex used in the equation. The equation has separate coefficients for female and male results.
- Enter serum creatinine in the unit printed on the report. The calculator converts µmol/L to mg/dL for the equation.
- Read the result as an estimate and compare it with the eGFR and range on the report.
What the result means, and what it does not
The result is an estimate of filtration. It can be useful for following a value over time, but it does not say what is causing a change, and it does not tell you whether the value is normal. Two people with the same eGFR can have different kidney health, because age, muscle mass, blood pressure, urine albumin, and other results all matter.
The calculator does not assign a stage, a category, or a risk label. Those are clinical classifications that depend on more than one number and on the equation and population used. If your report prints a stage or a comment, read that in the context of the report and discuss it with a qualified professional.
Limitations
- Adults only. The equation is not for children. Paediatric equations differ.
- Stable kidney function. The estimate assumes creatinine is stable. It is not designed for sudden kidney injury.
- Muscle mass. Creatinine comes from muscle. Very high or very low muscle mass can make the estimate less reliable.
- Pregnancy. The equation is not validated for pregnancy.
- Assay and calibration. Creatinine methods differ between laboratories. A small difference in creatinine can move the estimate.
- Equation choice. A laboratory may use a different equation or a cystatin C-based equation, and the value on the report may not match this calculator.
What this page is not
This calculator is a calculation from a published equation. It is not a diagnosis, a stage, a treatment recommendation, or medical advice. It does not replace the eGFR, range, or comment on your report. Verify the inputs against the original report and discuss the result with a qualified professional.