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Computes the FEV1/FVC ratio (%) = (FEV1 / FVC) x 100, the standard published spirometry index (the Tiffeneau-Pinelli index) used to help distinguish obstructive from restrictive ventilatory patterns. Commonly cited normal reference is roughly 70-80% or higher, generally declining somewhat with age. Pure arithmetic on given lab values. For general reference and educational purposes only — not a medical diagnosis. Consult a doctor for actual interpretation of spirometry results.
How it works
Enter FEV1 (forced expiratory volume in 1 second) and FVC (forced vital capacity) in liters. The tool divides FEV1 by FVC and multiplies by 100.
- Enter fEV1 (liters).
- Enter fVC (liters).
- Click Calculate to see your results.
Examples
FEV1 4.0 L, FVC 5.0 L
Ratio = (4.0/5.0) x 100 = 80% — within the commonly cited normal range.
Who should use it
- Reviewing a spirometry report.
- Obstructive vs. restrictive pattern education.
Industry applications
- Pulmonology reference
- Clinical education
Advantages
- Simple, standard formula.
- Quick reference against normal ranges.
Limitations
- Normal ranges vary by age, sex, height, and reference equation used.
- Does not replace clinical interpretation.
Common mistakes to avoid
- Interpreting the ratio alone without the percent-predicted FEV1 and FVC values, which a clinician also reviews.
Best practices
- Review the ratio alongside the absolute FEV1 and FVC values, not in isolation.
Tips
- A reduced ratio with a low FEV1 is commonly cited as obstructive, per standard spirometry teaching, but should always be confirmed by a clinician.