Cardiac Index is a measurement that helps assess the efficiency of the heart in pumping blood. It is calculated by dividing the Cardiac Output (the volume of blood the heart pumps per minute) by the body surface area. This value provides a more accurate reflection of heart function relative to an individual's size, making it useful in clinical settings. A normal Cardiac Index typically ranges from 2.5 to 4.0 liters per minute per square meter. Values outside this range can indicate potential heart problems, such as heart failure or shock, and may require further medical evaluation and intervention.