Cardiac Output Calculator

Calculate the volume of blood your heart pumps per minute using the Cardiac Output Calculator. Enter your heart rate (beats per minute) and stroke volume (mL per beat) to get your cardiac output in mL/min and L/min. You'll also see your cardiac index if body surface area is provided, making this a quick reference for physiology students and clinicians alike.

bpm

Normal resting heart rate is 60–100 beats per minute.

mL/beat

Average resting stroke volume is approximately 70 mL per beat.

m²

Optional. Used to calculate cardiac index. Average adult BSA is ~1.7 m².

Results

Cardiac Output

--

Cardiac Output (mL/min)

--

Cardiac Index

--

Blood Pumped Per Hour

--

Blood Pumped Per Day

--

Classification

--

Blood Volume Pumped Over Time

Frequently Asked Questions

What is cardiac output?

Cardiac output is the total volume of blood pumped by either the left or right ventricle of the heart per minute. It reflects how efficiently the heart is delivering oxygenated blood to the body's tissues. At rest, a healthy adult has a cardiac output of approximately 4.7–5 L/min.

How is cardiac output calculated?

Cardiac output (CO) is calculated using the simple formula: CO = Heart Rate × Stroke Volume. Heart rate is measured in beats per minute (bpm), and stroke volume is the amount of blood ejected per beat in milliliters (mL). The result is typically expressed in mL/min or L/min.

What is a normal cardiac output for adults?

A normal resting cardiac output for adults typically ranges from 4 to 8 L/min, with an average of about 5 L/min. It can increase dramatically during exercise — rising to 20–25 L/min in trained athletes — as both heart rate and stroke volume increase.

What is stroke volume and what affects it?

Stroke volume is the amount of blood ejected by one ventricle per heartbeat, normally around 70 mL at rest. It is affected by preload (the degree of ventricular filling before contraction), afterload (the resistance the heart must overcome), and myocardial contractility (the inherent strength of the heart muscle).

What is the cardiac index and why does it matter?

The cardiac index (CI) is cardiac output normalized for body surface area (BSA), expressed as L/min/m². It allows more meaningful comparison across individuals of different body sizes. A normal cardiac index ranges from 2.5 to 4.0 L/min/m². Values below 2.2 L/min/m² may indicate cardiogenic shock.

What conditions cause low cardiac output?

Low cardiac output can result from heart failure, cardiomyopathy, severe arrhythmias, myocardial infarction, hypovolemia, or tamponade. Symptoms include fatigue, shortness of breath, low blood pressure, and reduced urine output. Medical evaluation is needed to identify and treat the underlying cause.

Can cardiac output be too high?

Yes. High cardiac output states can occur in conditions like anemia, hyperthyroidism, sepsis, pregnancy, arteriovenous fistulas, and liver disease. While the heart pumps more blood, the oxygen-carrying capacity or vascular resistance is often reduced, meaning tissues may still be inadequately perfused.

How does exercise affect cardiac output?

During exercise, cardiac output can increase three- to fivefold above resting levels. Both heart rate and stroke volume rise in response to increased metabolic demands. Well-trained athletes tend to have a higher stroke volume even at rest, meaning their heart achieves the same cardiac output at a lower heart rate — a sign of cardiac efficiency.

More Health & Fitness Tools