Calculator Inputs
Use the responsive grid below. Large screens show three columns, smaller screens show two, and phones show one.
Formula Used
The calculator uses the adult 2012 CKD-EPI cystatin C equation. It estimates kidney filtration from serum cystatin C, age, and sex.
eGFR = 133 × min(Scys/0.8, 1)^-0.499 × max(Scys/0.8, 1)^-1.328 × 0.996^Age × 0.932 [if female]
- Scys = serum cystatin C in mg/L
- eGFR = indexed estimate in mL/min/1.73 m²
- min uses the smaller of
Scys/0.8or1 - max uses the larger of
Scys/0.8or1
When height and weight are entered, the page also estimates body surface area using the Mosteller method:
BSA = √((height in cm × weight in kg) / 3600)
De-indexed GFR = Indexed eGFR × (BSA / 1.73)
The indexed result supports CKD staging. The de-indexed value can help when absolute clearance matters for selected dosing or clinical review.
How to Use This Calculator
- Enter the patient’s serum cystatin C result in mg/L.
- Enter adult age and select sex.
- Optionally add height and weight to estimate body surface area and a de-indexed GFR.
- Choose whether the laboratory assay is standardized.
- Press Calculate eGFR to show the result above the form.
- Review the indexed eGFR, stage label, assay note, and optional de-indexed GFR.
- Use the CSV or PDF buttons to export the displayed summary.
- Pair the result with albuminuria, trend data, and clinical judgment.
Example Data Table
These examples show how different cystatin C values, ages, and sexes change the indexed estimate and GFR stage.
| Case | Cystatin C (mg/L) | Age | Sex | Indexed eGFR | Stage |
|---|---|---|---|---|---|
| Adult A | 0.82 | 42 | Female | 101.4 mL/min/1.73 m² | G1 |
| Adult B | 1.10 | 58 | Male | 69.1 mL/min/1.73 m² | G2 |
| Adult C | 1.65 | 67 | Female | 36.2 mL/min/1.73 m² | G3b |
| Adult D | 2.30 | 74 | Male | 24.3 mL/min/1.73 m² | G4 |
Frequently Asked Questions
1) What does this calculator estimate?
It estimates adult glomerular filtration rate from serum cystatin C, age, and sex. The main output is an indexed eGFR in mL/min/1.73 m².
2) Is this calculator suitable for children?
No. This page is restricted to adults aged 18 years or older. Pediatric kidney function estimation uses separate validated equations.
3) Why can height and weight be entered?
They allow estimation of body surface area. That lets the page convert indexed eGFR into a de-indexed absolute GFR for added clinical context.
4) What is the difference between indexed and de-indexed GFR?
Indexed GFR is normalized to 1.73 m² and is used for CKD staging. De-indexed GFR reflects estimated absolute clearance at the person’s body size.
5) Does a normal eGFR rule out kidney disease?
No. CKD diagnosis also depends on persistence and evidence of kidney damage, such as albuminuria, structural changes, or other abnormal findings.
6) Why does the page ask about assay standardization?
The equation performs best with standardized laboratory methods. If assay standardization is unknown or absent, the estimate should be interpreted more cautiously.
7) Can this result replace a medical evaluation?
No. It is a screening and documentation aid. Symptoms, trends, medications, albuminuria, and clinician assessment still matter.
8) What should be reviewed with the result?
Review urine albumin, prior kidney results, medication exposure, blood pressure, diabetes status, and whether the change appears acute or chronic.