What is a normal FEV1/FVC ratio?

A normal FEV1/FVC ratio is typically 0.70 (70%) or higher in adults. Values below 0.70 after bronchodilator use indicate fixed airflow obstruction consistent with COPD under GOLD criteria. In younger people, normal ratios may be slightly higher.

What is the difference between FEV1 and FVC?

FEV1 (Forced Expiratory Volume in 1 second) is the amount of air you can forcefully exhale in the first second of a spirometry test. FVC (Forced Vital Capacity) is the total amount of air you can forcefully exhale from full inspiration. The ratio compares how fast you exhale relative to your total lung capacity.

What does a low FEV1/FVC ratio mean?

A low ratio can support an obstructive ventilatory pattern, but the fixed 0.70 cutoff can over-classify some older adults and under-classify some younger adults. Ratio magnitude alone does not measure severity or distinguish COPD from asthma.

What are the GOLD severity stages?

GOLD classifies COPD obstruction by FEV1 percent predicted: GOLD 1 (Mild): FEV1 ≥ 80%; GOLD 2 (Moderate): 50% ≤ FEV1 < 80%; GOLD 3 (Severe): 30% ≤ FEV1 < 50%; GOLD 4 (Very Severe): FEV1 < 30%. This tool uses the ratio to confirm obstruction; FEV1 % predicted requires knowing the reference value.

Is this tool a medical diagnosis?

No. This calculator is for educational and informational purposes only. Always consult a qualified healthcare professional or respiratory therapist for interpretation of spirometry results and medical advice.

FEV1/FVC Ratio Calculator

Enter FEV1 and FVC values from the same spirometry test to calculate their ratio. The ratio alone does not grade COPD severity or diagnose asthma.

Spirometry Values

FEV1 — Forced Expiratory Volume in 1 second (L)

Typical range: 0.5 – 6.0 L

FVC — Forced Vital Capacity (L)

Typical range: 1.0 – 8.0 L

Interpretation Reference (Fixed 0.70 Ratio)

Normal (No Obstruction) ≥ 70%

Airflow Obstruction Indicated < 70%

Obstruction severity (GOLD stages 1–4) requires FEV1 % predicted, not the ratio magnitude.

Enter FEV1 and FVC values, then click Calculate.

Medical Disclaimer: This tool is for educational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider for the interpretation of spirometry results and clinical decisions.

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Summary

Enter FEV1 and FVC values from the same spirometry test to calculate their ratio. The ratio alone does not grade COPD severity or diagnose asthma.

How it works

Enter your FEV1 value in liters from your spirometry report.
Enter your FVC value in liters from the same test.
The calculator divides FEV1 by FVC and multiplies by 100 to get a percentage.
The result is compared with the fixed 0.70 reference used by this educational tool.
A result card explains the limitation of interpreting the ratio without reference values and clinical context.

Use cases

Screen spirometry results for obstructive lung patterns.
Check the arithmetic on a reported FEV1/FVC value.
Compare paired pre- and post-bronchodilator ratios for discussion with a clinician.
Learn how a ratio contributes to spirometry interpretation.
Educate patients on their spirometry report findings.
Prepare questions for a respiratory clinician.

Frequently Asked Questions

Last updated: 2026-09-22 · Reviewed by Nham Vu

FEV1/FVC Ratio Calculator

Spirometry Values

Interpretation Reference (Fixed 0.70 Ratio)

Your Result

Input Summary

Summary

How it works

Use cases

Frequently Asked Questions

FEV1/FVC Ratio Calculator

Use the FEV1/FVC Ratio Calculator

Spirometry Values

Interpretation Reference (Fixed 0.70 Ratio)

Your Result

Input Summary

Summary

How it works

Use cases

Frequently Asked Questions