What is the difference between FEV1 and FVC?

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.

What does GOLD staging mean for COPD patients?

GOLD staging is a commonly used COPD severity framework based on post-bronchodilator FEV1 percent predicted. On this page it is shown as broad context only; it does not replace the rest of the COPD assessment or decide treatment by itself.

Why does ethnicity affect predicted values?

Reference equations often include ethnicity adjustments because published prediction sets differ by population. Those adjustments are only part of the interpretation and do not replace the actual laboratory standard used by the testing center.

What is the Lower Limit of Normal (LLN)?

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.

Can spirometry differentiate asthma from COPD?

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.

How often should spirometry be repeated?

Repeat frequency depends on the clinical setting, disease being followed, and the testing protocol being used. The page is best used as a reference-value worksheet rather than as the source of the monitoring schedule itself.

Spirometry Predicted Value Calculator

Calculate predicted FEV1, FVC, and FEV1/FVC values from reference equations and compare measured results against those predicted values.

⚠️ Medical Disclaimer: Predicted values are reference estimates. Spirometry must be performed by trained personnel following ATS/ERS standards. Always interpret results with a qualified healthcare provider.

Patient Demographics

Sex

Age

years

Height

Height Unit

Ethnicity

Measured Values (optional)

Measured FEV1Leave empty for predicted only

Measured FVCLeave empty for predicted only

Predicted FEV1

3.63 L

Predicted FVC

4.74 L

Predicted FEV1/FVC

0.77

GOLD Severity Classification

Stage	FEV1 % Predicted	Typical Symptoms
GOLD 1 (Mild)	≥80%	Minimal or no symptoms; chronic cough possible
GOLD 2 (Moderate)	50–79%	Shortness of breath on exertion; chronic cough
GOLD 3 (Severe)	30–49%	Significant dyspnea; limited exercise capacity
GOLD 4 (Very Severe)	<30%	Severe dyspnea; impaired quality of life

Prerequisite: Post-bronchodilator FEV1/FVC < 0.70 confirms airflow limitation.

Spirometry Pattern Interpretation

Pattern	FEV1/FVC	FVC	Examples
Normal	Normal (≥0.70)	Normal (≥80%)	Healthy lungs
Obstructive	Reduced (<0.70)	Normal or mildly ↓	Asthma, COPD, bronchiectasis
Restrictive	Normal or ↑	Reduced (<80%)	Pulmonary fibrosis, scoliosis
Mixed	Reduced (<0.70)	Reduced (<80%)	COPD + fibrosis, severe asthma

Planning notes, formulas, and examples

About the Spirometry Predicted Value Calculator

The Spirometry Predicted Value Calculator computes expected FEV1, FVC, and FEV1/FVC values from age, sex, height, and ethnicity inputs. The main purpose of the page is to place measured spirometry values next to a reference value so the percent-predicted figures are easier to review.

The predicted values shown here use the NHANES III / Hankinson-style reference framework commonly used in adult spirometry interpretation. When measured values are entered, the page compares them with the reference values and shows broad obstruction/restriction context.

This is a comparison worksheet, not a full pulmonary-function interpretation engine. Formal spirometry interpretation still depends on test quality, bronchodilator status, lower-limit-of-normal context, symptoms, and the broader pulmonary workup.

When This Page Helps

Predicted values make spirometry easier to read because normal lung volumes vary substantially with age, sex, height, and ethnicity. This page keeps the reference values and percent-predicted calculations together so the measured numbers can be reviewed in context before the formal clinical interpretation is made.

How to Use the Inputs

Enter your age, sex, and height.
Select your ethnicity (affects reference equations).
View the predicted FEV1, FVC, and FEV1/FVC values.
Optionally enter your measured FEV1 and FVC to get percent-predicted and severity classification.
Review the obstruction/restriction pattern interpretation.
Discuss results with your pulmonologist or primary care provider.

Formula used

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%

Example Calculation

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.

Tips & Best Practices

Spirometry requires proper technique: maximal inspiration followed by forced, complete exhalation for at least 6 seconds. Poor effort invalidates results.
Post-bronchodilator spirometry (after albuterol) is required for COPD diagnosis. Pre-bronchodilator values alone may overestimate obstruction.
An FEV1/FVC ratio below 0.70 (or below the Lower Limit of Normal) indicates obstruction. Low FVC with normal ratio suggests restriction.
In elderly patients, the fixed 0.70 cutoff may over-diagnose COPD. The Lower Limit of Normal (LLN) approach adjusts for age-related decline.
Track FEV1 over time: normal decline is ~30 mL/year after age 25. Faster decline (>60 mL/year) suggests active disease progression.
Always ensure spirometry includes quality grades (ATS/ERS acceptability criteria). Only interpret tests with at least 3 acceptable maneuvers.

What the Percent-Predicted Values Show

Percent-predicted values help answer a simple question: how far is the measured number from the expected reference value for someone with similar basic characteristics? That makes them useful for comparison across time and across patients.

Limits of a Simple Pattern Label

A low FEV1/FVC ratio can suggest an obstructive pattern, and a low FVC with a preserved ratio can suggest a restrictive pattern, but formal interpretation still depends on test quality, bronchodilator context, and sometimes fuller lung-volume testing.

Best Use of This Page

Use the calculator to organize predicted values, measured values, and percent-predicted comparisons in one place. It is a reference worksheet, not a stand-alone diagnosis or severity engine.

Sources & Methodology

Last updated: March 28, 2026

Methodology

This page is a comparison worksheet. It applies the simplified NHANES III / Hankinson-style adult reference equations already implemented in the calculator, then compares optional measured FEV1 and FVC values against those reference numbers to show percent-predicted values and a broad fixed-ratio pattern label. Because the underlying page uses legacy race/ethnicity adjustments and a fixed 0.70 obstruction cutoff, the output should be treated as reference context rather than as a laboratory-grade interpretation or lower-limit-of-normal assessment.

Sources

Spirometric Reference Values from a Sample of the General U.S. Population (Centers for Disease Control and Prevention) — NHANES III reference paper underlying the style of adult predicted equations used on this page.
Standardization of Spirometry 2019 Update. An Official American Thoracic Society and European Respiratory Society Technical Statement (American Thoracic Society / European Respiratory Society) — Current technical standard for spirometry performance and interpretation context.
ATS Publishes Official Statement on Race, Ethnicity and Pulmonary Function Test Interpretation (American Thoracic Society) — Relevant because the calculator still uses legacy ethnicity adjustments and should be read as a simplified worksheet.

Frequently Asked Questions

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.