Cardiac Output Calculator
Calculates cardiac output in liters per minute from heart rate (bpm) and stroke volume (mL). Used clinically to assess how efficiently the heart is pumping blood to meet the body's demands.
About this calculator
Cardiac output (CO) is the volume of blood the heart pumps per minute. It is calculated as: CO (L/min) = (Heart Rate × Stroke Volume) / 1000. Heart rate is measured in beats per minute (bpm) and stroke volume is the volume of blood ejected per beat in milliliters (mL). Dividing by 1000 converts the result from mL/min to L/min. A healthy adult at rest has a typical cardiac output of 4–8 L/min. Stroke volume itself depends on preload (ventricular filling), afterload (resistance to ejection), and myocardial contractility. Cardiac output is a central parameter in cardiovascular medicine, used to evaluate heart failure, guide fluid resuscitation in critical care, and monitor patients during surgery. It can be measured clinically using echocardiography or thermodilution techniques.
How to use
Suppose a patient has a resting heart rate of 72 bpm and an echocardiographically measured stroke volume of 70 mL per beat. Apply the formula: CO = (heartRate × strokeVolume) / 1000 = (72 × 70) / 1000 = 5040 / 1000 = 5.04 L/min. This falls comfortably within the normal resting range of 4–8 L/min. During intense exercise, if heart rate rises to 160 bpm and stroke volume increases to 110 mL, CO = (160 × 110) / 1000 = 17600 / 1000 = 17.6 L/min, reflecting the dramatic increase in circulatory demand.
Frequently asked questions
What is a normal cardiac output range for a healthy adult at rest?
A healthy adult at rest typically has a cardiac output between 4 and 8 liters per minute, with an average around 5 L/min. This value is often normalized to body surface area as the cardiac index (CI = CO / BSA), with a normal range of 2.5–4.0 L/min/m². Values below 2.2 L/min/m² may indicate cardiogenic shock, while elevated values can reflect sepsis, anemia, or hyperthyroidism.
How does exercise affect cardiac output and stroke volume?
During vigorous exercise, cardiac output can increase 4–7 fold in trained athletes, reaching 20–40 L/min. Both heart rate and stroke volume increase, though heart rate rises more dramatically. Stroke volume increases due to greater venous return (Frank-Starling mechanism) and stronger myocardial contractility driven by sympathetic stimulation. Regular aerobic training enlarges the ventricles and improves stroke volume at rest, allowing athletes to maintain high cardiac output at lower heart rates.
Why is cardiac output important in diagnosing and managing heart failure?
In heart failure, the heart cannot pump sufficient blood to meet the body's metabolic needs, leading to reduced cardiac output. Measuring CO helps clinicians classify heart failure severity, guide treatment decisions such as diuretics, vasodilators, or inotropes, and monitor response to therapy. In intensive care, continuous CO monitoring via pulmonary artery catheters or advanced echocardiography guides fluid and vasopressor management in critically ill patients to prevent organ damage from inadequate perfusion.