Respiratory capacities refer to the maximum amount of air that can be inhaled and exhaled, generally measured in liters. First, inspiratory capacity or IC refers to the maximum air breathed in with full effort. It is calculated by adding the tidal volume and inspiratory reserve volume. A normal IC value ranges from 2.4 to 3.6 liters. Functional residual capacity, or FRC, is the air remaining in the lungs after a normal exhalation—the normal values of FRC range from 2.6 to 3.2 liters. Vital capacity, or VC, is the maximum air one can exhale following a full inhalation. A normal value for VC is 4 to 5 liters. Total lung capacity or TLC represents all volumes within both lungs combined at any given time, including tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume. It determines an individual's total respiratory capability by indicating their overall lung size and capacity for gas exchange between inhaled oxygen and exhaled carbon dioxide. A normal value for TLC ranges from 6 to 7 liters.