Vital Capacity Calculator

What is Vital Capacity (VC)?

Vital Capacity (VC) is the maximum volume of air a person can exhale after a maximal inhalation. It represents the functional respiratory reserve of the lungs and is a primary diagnostic parameter measured during spirometry pulmonary function tests.

Vital capacity is the sum of three component lung volumes:

$$\text{Vital Capacity (VC)} = \text{IRV} + \text{TV} + \text{ERV}$$

Inspiratory Reserve Volume (IRV): Maximum extra volume that can be inhaled above normal tidal volume (~2.5 - 3.5 L).
Tidal Volume (TV): Volume inhaled or exhaled with each normal breath (~0.5 L).
Expiratory Reserve Volume (ERV): Maximum volume that can be forcefully exhaled below resting tidal level (~1.0 - 1.5 L).

Predictive Clinical Equations (Baldwin & Crapo)

A person's expected vital capacity depends heavily on their biological sex, age, and standing height. Two validated reference formulas used in clinical screening include:

1. Baldwin Regression Equation

Male: $\text{VC (mL)} = (27.63 - 0.112 \times \text{Age}) \times \text{Height (cm)}$
Female: $\text{VC (mL)} = (21.78 - 0.101 \times \text{Age}) \times \text{Height (cm)}$

2. Crapo / ATS Reference Equation (FVC)

Male: $\text{FVC (L)} = 0.0564 \times \text{Height (cm)} - 0.025 \times \text{Age} - 4.241$
Female: $\text{FVC (L)} = 0.0443 \times \text{Height (cm)} - 0.026 \times \text{Age} - 2.887$

Clinical Interpretation of Vital Capacity

% of Predicted VC	Classification	Clinical Significance
≥ 80%	Normal	Normal ventilatory volume within expected population limits.
65% - 79%	Mild Reduction	Early restrictive lung pattern, chest wall stiffness, or mild weakness.
50% - 64%	Moderate Restriction	Significant pulmonary fibrosis, scoliosis, or diaphragm dysfunction.
< 50%	Severe Restriction	Severe respiratory compromise requiring comprehensive pulmonary evaluation.

For full component lung volume breakdown and ventilatory parameters, check out our Lung Capacity Calculator, Peak Flow Calculator, and Tidal Volume Calculator.

Frequently Asked Questions

What is the difference between Vital Capacity (VC) and Forced Vital Capacity (FVC)?

Slow Vital Capacity (SVC or VC) is measured during relaxed, unforced exhalation, while Forced Vital Capacity (FVC) requires maximal effort and rapid forceful exhalation. In healthy individuals, VC and FVC are virtually identical. In obstructive diseases like COPD, air trapping can cause FVC to be lower than slow VC.

Why does vital capacity decline with age?

As we age, lung parenchyma loses elastic recoil, respiratory muscles weaken, and the thoracic rib cage stiffens. This causes vital capacity to decrease by approximately 20 to 30 mL per year after the age of 25.

What causes low vital capacity?

Reduced vital capacity is commonly caused by restrictive lung diseases (idiopathic pulmonary fibrosis, sarcoidosis), neuromuscular disorders (ALS, myasthenia gravis, Guillain-Barré), thoracic wall deformities (kyphoscoliosis), pleural effusion, or severe obesity.

What is the average vital capacity for healthy adults?

For healthy adult males, normal vital capacity averages between 4.0 and 5.5 Liters (depending on height). For healthy adult females, normal vital capacity averages between 3.0 and 4.2 Liters.

Report

What is Vital Capacity (VC)?

Predictive Clinical Equations (Baldwin & Crapo)

1. Baldwin Regression Equation

2. Crapo / ATS Reference Equation (FVC)

Clinical Interpretation of Vital Capacity

Frequently Asked Questions

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