Calculate predicted FEV1, FVC, and FEV1/FVC ratio based on age, sex, height, and ethnicity. Classify airway obstruction severity using GOLD and ATS/ERS criteria.
The Spirometry Predicted Value Calculator computes expected FEV1 (Forced Expiratory Volume in 1 second), FVC (Forced Vital Capacity), and FEV1/FVC ratio based on age, sex, height, and ethnicity. Spirometry is the gold standard pulmonary function test used to diagnose and monitor obstructive lung diseases (asthma, COPD) and restrictive conditions (pulmonary fibrosis, neuromuscular disease).
Predicted values use the widely-adopted NHANES III/Hankinson reference equations for adults aged 8–80+ years. By entering your actual measured spirometry values, this calculator determines your percentage of predicted and classifies the degree of abnormality using the GOLD (Global Initiative for Obstructive Lung Disease) severity staging system.
Understanding where you fall relative to predicted values helps clinicians determine if your lung function is normal, identify the type of impairment (obstructive vs. restrictive), and track disease progression over time. Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation. By automating the calculation, you save time and reduce the risk of costly errors in your planning and decision-making process.
Spirometry results cannot be interpreted in isolation because normal lung function varies substantially with age, sex, height, and ethnicity. A 25-year-old tall male and a 70-year-old short female have dramatically different expected values. Comparing measured spirometry to individualized predicted values reveals whether your lung function is truly abnormal and to what degree. This is essential for diagnosing COPD, monitoring asthma, surgical risk assessment, and disability evaluation.
Hankinson/NHANES III Reference Equations (adults): Males (Caucasian): FEV1 = 0.5536 − 0.01303 × Age − 0.000172 × Age² + 0.00014098 × Ht² FVC = −0.1933 + 0.00064 × Age − 0.000269 × Age² + 0.00018642 × Ht² Females (Caucasian): FEV1 = 0.4333 − 0.00361 × Age − 0.000194 × Age² + 0.00011496 × Ht² FVC = −0.3560 + 0.01870 × Age − 0.000382 × Age² + 0.00014815 × Ht² Ht = height in cm; Age in years Ethnicity corrections: • African American: multiply by 0.88 • Asian/Hispanic: multiply by 0.93 GOLD Classification (post-bronchodilator FEV1/FVC < 0.70): • GOLD 1 (Mild): FEV1 ≥ 80% predicted • GOLD 2 (Moderate): 50–80% • GOLD 3 (Severe): 30–50% • GOLD 4 (Very Severe): < 30%
Result: FEV1: 59% predicted (GOLD 2 — Moderate) | FVC: 82% predicted | Ratio: 0.60
The predicted FEV1 for a 55-year-old Caucasian male at 175 cm is approximately 3.55 L. A measured FEV1 of 2.1 L gives 59% of predicted, and with FEV1/FVC of 0.60 (below 0.70), this confirms obstructive disease classified as GOLD Stage 2 (Moderate). FVC at 82% suggests no significant restrictive component.
Obstructive pattern (asthma, COPD, bronchiectasis): FEV1/FVC is reduced below normal, while FVC may be normal or only mildly reduced. The hallmark is disproportionate reduction in flow rates. Restrictive pattern (pulmonary fibrosis, neuromuscular disease, chest wall deformity): FVC is significantly reduced, but FEV1/FVC is normal or increased because both volumes decrease proportionally. Mixed patterns (both obstruction and restriction) require full pulmonary function testing with lung volumes (TLC) for definitive classification.
Beyond numeric values, the shape of the flow-volume loop provides diagnostic information. A scooped (concave) expiratory limb suggests small airway obstruction. A plateau in the inspiratory or expiratory limb suggests fixed or variable upper airway obstruction. Normal loops show a sharp peak flow followed by a linear decline.
OSHA mandates spiral spirometry monitoring for workers exposed to certain respiratory hazards (asbestos, silica, coal dust, cotton dust). Baseline testing at hire and annual follow-up allows detection of accelerated lung function decline attributable to workplace exposures, enabling early intervention and removal from exposure.
FEV1 is the volume of air you can forcefully exhale in the first one second. FVC is the total volume exhaled during the entire forced breath. In healthy lungs, you can exhale about 75–80% of your total in the first second (FEV1/FVC = 0.75–0.80). In obstructive disease (asthma, COPD), the ratio drops because the narrowed airways slow exhalation. In restrictive disease, both FEV1 and FVC decrease, but the ratio remains normal or elevated.
GOLD staging classifies COPD severity based on post-bronchodilator FEV1 percent predicted: Stage 1 (Mild, ≥80%) may have minimal symptoms; Stage 2 (Moderate, 50–80%) causes shortness of breath with exertion; Stage 3 (Severe, 30–50%) significantly limits activity; Stage 4 (Very Severe, <30%) severely impairs quality of life. Treatment intensity escalates with each stage.
Studies consistently show that predicted lung volumes differ by ethnicity due to differences in body proportions, particularly the ratio of trunk length to height. African Americans and Asian Americans tend to have lower lung volumes relative to height compared to Caucasians of the same height and age. The reference equations include correction factors to account for these well-documented physiological differences.
The LLN is the 5th percentile of the predicted value distribution for a person's age, sex, height, and ethnicity. Using LLN instead of a fixed FEV1/FVC cutoff of 0.70 avoids over-diagnosing COPD in elderly patients (whose ratio naturally decreases with age) and under-diagnosing it in younger patients. Current ATS/ERS guidelines recommend LLN, while GOLD still uses the fixed 0.70 cutoff.
Not definitively on its own, but bronchodilator response helps. In asthma, FEV1 typically improves by ≥12% AND ≥200 mL after albuterol (significant reversibility). In COPD, improvement is usually less dramatic. However, some COPD patients show significant reversibility, and some asthmatics don't. Clinical history, imaging, and biomarkers (eosinophils, FeNO) help differentiate the two.
For stable COPD: annually to track FEV1 decline. For asthma: at diagnosis, after treatment change, and every 1–2 years when stable. For occupational lung disease screening: annually or as mandated by workplace regulations. More frequent testing during exacerbations or treatment adjustments. Spirometry should always be performed by a trained technician following ATS/ERS quality standards.