# eGFR calculator (CKD-EPI 2021)

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An estimate of kidney filtration from age, sex, and serum creatinine, using the race-free 2021 equation.

This is the Markdown version of https://doctano.com/tools/egfr-calculator. The HTML page is the canonical version and carries the interactive calculator.

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:

```text
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. |

Source: [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;385:1737-1749.](https://doi.org/10.1056/NEJMoa2102953)

## How to use it

1. Enter the age at the time the sample was collected, not the age today if the report is old.
2. Select the sex used in the equation. The equation has separate coefficients for female and male results.
3. Enter serum creatinine in the unit printed on the report. The calculator converts µmol/L to mg/dL for the equation.
4. 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.

## eGFR calculator questions

**What equation does this eGFR calculator use?**

It uses the CKD-EPI 2021 creatinine equation without a race coefficient, published by Inker and colleagues in the New England Journal of Medicine. The calculator states the equation version so the result can be checked.

**Is eGFR the same as GFR?**

No. GFR is a measured filtration rate. eGFR is an estimate calculated from serum creatinine, age, and sex, normalized to a body surface area of 1.73 square metres. It is an approximation and can differ from a measured value.

**Can I use this calculator for a child?**

No. This equation is for adults. Children have different equations and different body-size assumptions, so a paediatric result needs a paediatric method and a clinician's reading.

**Why is there no normal range on this page?**

Kidney function is interpreted with age, history, urine albumin, and the clinical context, and reference values differ between laboratories and equations. This page does not print a range or stage. Use the range or comment printed on your report.

**Why does the calculator ask for sex?**

Sex is one of the variables in the CKD-EPI 2021 equation, which uses different coefficients for female and male results. The calculator asks because the equation requires it, not to make a judgment about identity.

## Limits

**This is a calculation, not a diagnosis.** eGFR is an estimate from a published equation. It does not stage kidney disease, does not replace the value on your report, and does not tell you what to do. Discuss the result with a qualified professional.

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