Example data table
| Scenario | FEV1 (L) | FVC (L) | FEV1/FVC (%) | Note |
|---|---|---|---|---|
| Typical adult example | 3.20 | 4.00 | 80.00 | Often above common thresholds. |
| Lower ratio example | 1.80 | 3.20 | 56.25 | May indicate airflow limitation if confirmed. |
| Normal ratio, low FVC example | 2.60 | 3.10 | 83.87 | Reduced FVC can suggest restriction or effort issues. |
| Post-test improvement example | 2.10 | 3.30 | 63.64 | Compare with post-test inputs for changes. |
Examples are illustrative and not medical advice.
Formula used
- Ratio (%) = (FEV1 ÷ FVC) × 100
- Percent predicted (%) = (Measured ÷ Predicted) × 100 (when predicted is provided)
- Change after test = Post − Pre, with percent change ((Post − Pre) ÷ Pre) × 100
- Classic bronchodilator response screen checks for ≥12% and ≥200 mL change in FEV1 or FVC.
How to use this calculator
- Enter pre-test FEV1 and FVC from your spirometry report.
- Select the input unit that matches your report (L or mL).
- Choose a threshold mode: fixed 70%, your LLN, or a custom threshold.
- Optional: add predicted values to estimate percent predicted.
- Optional: add post-test values to view changes and post-test ratio.
- Click Calculate. Results appear above the form, with export buttons.