Cardiac Index Calculator

Cardiac index is a hemodynamic measurement that relates the amount of blood the heart pumps each minute to a person's body surface area. Cardiac output alone is useful, but larger bodies generally require more blood flow than smaller bodies. Dividing output by body surface area makes comparisons between patients more meaningful. Clinicians use cardiac index alongside blood pressure, oxygen delivery, examination findings, and other measurements when evaluating cardiovascular performance. This calculator first determines cardiac output by multiplying heart rate in beats per minute by stroke volume in milliliters per beat, then dividing by 1,000 to express the answer in liters per minute. It estimates body surface area with the Mosteller equation: the square root of height in centimeters multiplied by weight in kilograms and divided by 3,600. Finally, cardiac output is divided by body surface area to produce cardiac index in liters per minute per square meter. A commonly cited resting cardiac index range for adults is approximately 2.5 to 4.0 L/min/m², although reference intervals vary with clinical setting, age, activity, temperature, medication, pregnancy, and measurement technique. A value outside that range is not a diagnosis by itself. Low values may occur with impaired pumping, reduced circulating volume, or high vascular resistance, while high values may accompany exercise, fever, anemia, pregnancy, or distributive states. The accuracy of the result depends directly on the measurements entered. Stroke volume may be estimated by echocardiography or measured using invasive methods, and each technique has assumptions and sources of error. Height and weight should represent the patient at the time of assessment. The Mosteller formula is practical and widely used, but other body surface area equations can produce slightly different values. Use this result as an educational calculation or a transparent check of clinical arithmetic, not as a substitute for professional interpretation. Hemodynamic decisions require the full clinical picture and often repeated measurements to identify trends. Urgent symptoms such as chest pain, severe breathlessness, fainting, confusion, or signs of shock require immediate medical assessment regardless of a calculated number.