Calculator inputs
Example data table
| # | Creatinine | Unit | Age | Sex | ACR | ACR Unit | Expected pattern |
|---|---|---|---|---|---|---|---|
| 1 | 0.9 | mg/dL | 34 | Female | 12 | mg/g | Higher eGFR, likely G1–G2 |
| 2 | 1.4 | mg/dL | 62 | Male | 85 | mg/g | Moderate eGFR, possible G3a |
| 3 | 165 | µmol/L | 70 | Female | 35 | mg/mmol | Lower eGFR, higher albuminuria risk |
| 4 | 2.6 | mg/dL | 58 | Male | 420 | mg/g | Advanced stage, likely G4–G5 risk |
| 5 | 1.1 | mg/dL | 45 | Female | — | — | Stage only, albuminuria not assessed |
Examples are illustrative and not clinical test cases.
Formula used
This tool estimates kidney filtration using the CKD-EPI 2021 creatinine equation (race-free):
κ = 0.7 (female), 0.9 (male) • α = -0.241 (female), -0.302 (male) • SexFactor = 1.012 (female), 1.0 (male)
Staging uses G categories: G1 ≥90, G2 60–89, G3a 45–59, G3b 30–44, G4 15–29, G5 <15 (mL/min/1.73m²). If ACR is entered, albuminuria categories are A1 <30, A2 30–300, A3 >300 (mg/g).
How to use this calculator
- Enter serum creatinine, select the correct unit.
- Enter age and choose sex for coefficient selection.
- Optionally add urine ACR to view A category and risk.
- Press Calculate to see results above the form.
- Use CSV/PDF buttons to export your calculation summary.
Clinical interpretation of eGFR values
eGFR as a standardized filtration estimate
eGFR is reported in mL/min/1.73m² to normalize for body surface area. This calculator uses serum creatinine, age, and sex to estimate filtration using coefficients κ (0.7 female, 0.9 male) and α (-0.241 female, -0.302 male), then applies an age factor of 0.9938 per year. The final multiplier 142 scales the estimate to the standardized unit. For adults, results are most comparable when creatinine is enzymatically standardized across laboratories.
G-stage thresholds used for classification
Stages are determined from the estimated value: G1 is ≥90, G2 is 60–89, G3a is 45–59, G3b is 30–44, G4 is 15–29, and G5 is <15. These cut points help standardize reporting and support consistent clinical communication. A 1–2 mL/min difference around 60 or 45 can change the label, so repeat testing matters.
Albuminuria adds risk stratification
If urine albumin-to-creatinine ratio is provided, the tool assigns A1 (<30 mg/g), A2 (30–300 mg/g), or A3 (>300 mg/g). For users entering mg/mmol, the calculator converts using an approximate factor of 8.84 to align values to mg/g for categorization. Pairing G and A categories supports a practical risk summary used in many clinical pathways.
Worked example with unit conversion
Consider creatinine 165 µmol/L, age 70, female. The conversion to mg/dL is 165 ÷ 88.4 ≈ 1.87 mg/dL. That converted value is used in the equation to produce eGFR, which is rounded to one decimal for display. For documentation, record both the entered unit and the converted mg/dL used internally.
Using results for monitoring and documentation
Trend interpretation benefits from consistent lab methods and repeated measurements. Clinically, CKD requires abnormal kidney markers persisting for ≥3 months. Use the CSV/PDF exports to document inputs, the computed eGFR, and the assigned categories during follow-up discussions. If values move from G2 to G3a, confirm hydration status, medications, and any intercurrent illness.
Important limitations and context checks
Creatinine-based estimates can shift with muscle mass, diet, and acute illness. Interpret results alongside symptoms, blood pressure, diabetes control, medication exposure, and urinalysis. When values sit near a boundary (for example 59.9 vs 60.1), treat staging as approximate and confirm with repeat testing. Consider cystatin C or measured clearance when estimates do not match the clinical picture.
FAQs
1) What does eGFR represent?
It estimates kidney filtration from creatinine, age, and sex, reported as mL/min/1.73m². It is an estimate, not a direct measurement, and should be interpreted with clinical context and repeat testing.
2) Why can my stage change between visits?
Hydration, lab variability, diet, medications, and intercurrent illness can change creatinine and eGFR. Small shifts near boundaries like 60 or 45 can change the label, so trends over time are more meaningful.
3) Do I need ACR to use the calculator?
No. ACR is optional. If entered, the calculator adds albuminuria category (A1–A3) and a simple combined risk summary. Without ACR, it still provides eGFR and the G stage.
4) Which creatinine unit should I choose?
Select the unit shown on your lab report. The tool converts µmol/L to mg/dL using 88.4. Using the wrong unit can significantly distort eGFR and stage classification.
5) Is this appropriate for acute kidney injury?
Not reliably. In acute kidney injury, creatinine may be changing rapidly, and eGFR equations assume steady state. Use clinical assessment and clinician-guided testing rather than relying on a single estimate.
6) When should I seek professional advice?
If eGFR is persistently below 60, ACR is elevated, or symptoms exist, discuss results with a clinician. Urgent evaluation is needed for rapid decline, swelling, shortness of breath, or confusion.