FEV1/FVC Ratio Calculator

Calculate the Tiffeneau index to assess pulmonary function and detect airflow obstruction

Critical Medical Disclaimer

This calculator is for educational purposes only and should NOT be used for medical diagnosis or treatment decisions.

FEV1/FVC ratio interpretation requires professional medical expertise
Spirometry results must be evaluated by qualified healthcare providers
Other factors (symptoms, medical history, physical exam) are essential for diagnosis
Always consult a pulmonologist or physician for proper interpretation

Calculate FEV1/FVC Ratio

FEV1 (Forced Expiratory Volume in 1 Second)

Volume of air exhaled in the first second of forced expiration

FVC (Forced Vital Capacity)

Total volume of air that can be exhaled after maximum inspiration

Patient Age (optional for interpretation)

Age affects normal reference values (≥65 years: normal ≥65%, <65 years: normal ≥70%)

FEV1/FVC Ratio Results

0.0%

Tiffeneau Index

FEV1/FVC × 100

⏳ Pending

Interpretation: Enter values to calculate

Formula: FEV1/FVC Ratio = (FEV1 ÷ FVC) × 100%

Values used: FEV1 = 0.00L, FVC = 0.00L

Clinical Significance

Example Calculation

Normal Adult Male Example

Age: 45 years old

FEV1: 3.2 L (measured during spirometry)

FVC: 4.1 L (measured during spirometry)

Calculation: (3.2 ÷ 4.1) × 100% = 78.0%

Interpretation: Normal (≥70% for age <65)

COPD Patient Example

Age: 62 years old, smoker

FEV1: 1.8 L (reduced)

FVC: 3.2 L (normal or slightly reduced)

Calculation: (1.8 ÷ 3.2) × 100% = 56.3%

Interpretation: Moderate obstruction (<70%)

Reference Values

FEV1/FVC Normal Values

Age < 65 years:≥ 70%

Age ≥ 65 years:≥ 65%

Individual Values

Normal FEV1:≥ 80% predicted

Normal FVC:≥ 80% predicted

COPD Staging

Stage I - Mild

FEV1/FVC < 70% + FEV1 ≥ 80% predicted

Stage II - Moderate

FEV1/FVC < 70% + 50% ≤ FEV1 < 80%

Stage III - Severe

FEV1/FVC < 70% + 30% ≤ FEV1 < 50%

Stage IV - Very Severe

FEV1/FVC < 70% + FEV1 < 30%

Interpretation Guide

✓

Ratio ≥70% (or ≥65% if age ≥65): Normal lung function

⚠

Ratio 50-69%: Mild to moderate obstruction

⚠

Ratio <50%: Severe obstruction

ⓘ

Always consider patient symptoms and history

Understanding FEV1/FVC Ratio

What is the FEV1/FVC Ratio?

The FEV1/FVC ratio, also known as the Tiffeneau index, is a key measurement in pulmonary function testing. It compares how much air you can forcibly exhale in one second (FEV1) to the total amount you can exhale after taking the deepest breath possible (FVC).

Clinical Applications

•Diagnose and monitor COPD (Chronic Obstructive Pulmonary Disease)
•Assess asthma severity and control
•Evaluate respiratory disability
•Monitor disease progression

Spirometry Procedure

Step 1: Patient takes the deepest breath possible

Step 2: Exhales as hard and fast as possible into the spirometer

Step 3: Continues exhaling until completely empty

Step 4: Machine measures FEV1 (first second) and FVC (total volume)

Important: Test should be performed by trained technicians and interpreted by qualified healthcare providers.

Interpretation Guidelines

Normal Function

FEV1/FVC ≥ 70% (or ≥65% if age ≥65 years) indicates normal lung function with no significant airflow obstruction.

Obstruction Present

FEV1/FVC < 70% suggests airflow obstruction, commonly seen in COPD, asthma, or other respiratory conditions.

Additional Testing

Abnormal results require comprehensive evaluation including medical history, physical exam, and additional tests.