Cardiac Output Calculator
HealthCalculate cardiac output in liters per minute from heart rate and stroke volume, with the normal 4 to 8 L/min resting adult range shown for comparison.
Heart Rate
bpm
30 bpm220 bpm
Stroke Volume
mL
20 mL200 mL
Cardiac Output
0L/min
Normal Range: 4-8 L/min
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Not a substitute for clinical monitoring. Cardiac output should be interpreted alongside other hemodynamic data by a qualified healthcare provider, especially in critical care settings.
What is a Cardiac Output?
A Cardiac Output Calculator computes the total volume of blood the heart pumps per minute by multiplying heart rate by stroke volume, expressed in liters per minute (L/min). Cardiac output is one of the most basic and important measures of cardiovascular function, reflecting how well the heart is meeting the body's blood flow demands moment to moment.
The relationship is straightforward — a faster heart rate or a larger stroke volume both increase cardiac output — but interpreting a given cardiac output value requires comparing it to the normal resting range of roughly 4 to 8 liters per minute. This calculator applies the standard formula directly to your heart rate and stroke volume inputs.
How to use this Cardiac Output calculator
- Enter the Heart Rate in beats per minute (bpm).
- Enter the Stroke Volume in milliliters (mL), typically obtained from echocardiography or hemodynamic monitoring.
- Review the calculated Cardiac Output in the results panel.
- Check the Normal Range Check to see whether the result falls within the typical 4-8 L/min resting range.
- Discuss any below- or above-normal result with a qualified healthcare provider, especially alongside symptoms or other clinical findings.
Formula & Methodology
Cardiac Output (L/min) = (Heart Rate × Stroke Volume) ÷ 1000 This is the standard physiological formula for cardiac output (Guyton & Hall, Textbook of Medical Physiology), where heart rate is in beats per minute and stroke volume is in milliliters. The normal resting adult range is approximately 4-8 L/min. Worked example: A heart rate of 75 bpm with a stroke volume of 65 mL gives a cardiac output of (75 × 65) ÷ 1000 = 4.88 L/min, which falls within the normal resting range.
Frequently Asked Questions
Cardiac output is the total volume of blood the heart pumps per minute, calculated as heart rate multiplied by stroke volume, expressed in liters per minute (L/min). It's one of the most fundamental measures of how well the heart is delivering blood to meet the body's needs.
A normal resting adult cardiac output is approximately 4 to 8 liters per minute, though this varies with body size, fitness level, and activity. Cardiac output increases substantially during exercise to meet the body's higher oxygen demand.
Stroke volume is the amount of blood ejected by the left ventricle with each heartbeat, typically measured in milliliters (mL) using echocardiography or invasive hemodynamic monitoring. It reflects both how much blood fills the heart between beats and how effectively the heart contracts to eject it.
A low cardiac output can result from reduced heart rate (bradycardia), reduced stroke volume from weakened heart muscle (heart failure), significant blood loss, or conditions affecting how well the heart fills between beats. Persistently low cardiac output can lead to symptoms like fatigue, shortness of breath, and poor organ perfusion.
Elevated cardiac output can occur with exercise, fever, anemia, hyperthyroidism, pregnancy, or conditions causing the body to demand more blood flow than usual. In some of these conditions, the heart is working harder to meet increased metabolic or oxygen delivery needs.
Cardiac output is the total blood volume pumped per minute regardless of body size, while the [Cardiac Index Calculator](/cardiac-index-calculator/) divides that output by body surface area, allowing fairer comparison between people of different sizes. A cardiac output of 5 L/min might be adequate for a small person but insufficient for someone much larger, which is why cardiac index is often the more clinically meaningful number.
No, heart rate is only half of the equation — a fast heart rate with a very low stroke volume can still produce reduced cardiac output, as seen in some forms of heart failure. Both heart rate and stroke volume need to be considered together to understand true cardiac output.
Common methods include echocardiography (using stroke volume and heart rate), thermodilution via a pulmonary artery catheter, and pulse contour analysis from an arterial line, each with different levels of invasiveness and accuracy. The method chosen typically depends on the clinical setting and how critically ill the patient is.
Blood pressure is a function of both cardiac output and systemic vascular resistance, so a change in cardiac output doesn't always translate directly into a proportional blood pressure change. Checking your [Blood Pressure Calculator](/blood-pressure-calculator/) result alongside cardiac output gives a more complete hemodynamic picture.
Yes, cardiac output typically decreases slightly when standing due to blood pooling in the legs and rises substantially during physical activity to meet increased oxygen demand. This is why cardiac output measurements are usually taken with the patient at rest in a standardized position for consistency.
While direct cardiac output measurement is mostly used in critical care, cardiology, and cardiac surgery settings, understanding the heart rate × stroke volume relationship helps explain why conditions like heart failure or severe anemia cause fatigue and reduced exercise tolerance. It's a foundational physiology concept taught across medical and nursing education.
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