What is cardiac output?

Cardiac output (CO) is the volume of blood pumped by the heart per minute, measured in liters per minute (L/min). It's calculated by multiplying heart rate (beats per minute) by stroke volume (volume of blood ejected per beat): CO = HR × SV. Normal resting cardiac output is approximately 5 L/min for adults, though it varies with body size, fitness level, and activity.

What is a normal cardiac output?

Normal resting cardiac output for adults is approximately 4-8 L/min, with an average around 5 L/min. However, 'normal' varies significantly based on body size (larger people have higher CO), age, fitness level, and activity. During intense exercise, cardiac output can increase to 20-30 L/min in average individuals and up to 35-40 L/min in elite endurance athletes.

How do heart rate and stroke volume affect cardiac output?

Cardiac output is the product of heart rate and stroke volume. Either can increase to raise CO: during exercise, both typically increase. However, there's a balance - if heart rate becomes too high, there's insufficient time for the ventricles to fill, actually reducing stroke volume and limiting CO increase. This is why extremely rapid heart rates (over 180-200 bpm) may reduce cardiac efficiency.

What is cardiac index and how is it different from cardiac output?

Cardiac index (CI) is cardiac output normalized for body surface area, calculated as CI = CO / BSA (body surface area in m²). Normal CI is 2.5-4.0 L/min/m². Cardiac index allows fairer comparison between individuals of different sizes - a 5 L/min CO is excellent for a small person but low for someone much larger. Medical professionals often use CI for more accurate assessment.

When would a doctor measure cardiac output?

Cardiac output measurement is important in critical care, heart failure management, shock assessment, cardiac surgery monitoring, and evaluating heart function during stress tests. Low cardiac output indicates the heart isn't meeting the body's needs, seen in conditions like heart failure, severe valve disease, or shock. High cardiac output occurs in conditions like sepsis, anemia, or hyperthyroidism.

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Cardiac Output Calculator

Calculate the volume of blood pumped by the heart per minute.

Heart Rate (bpm)

Stroke Volume (mL)

How to Use This Calculator

Measure Heart Rate

Enter your heart rate in beats per minute (bpm). This can be measured by taking your pulse for 60 seconds, or count for 15 seconds and multiply by 4. For resting cardiac output, measure while seated and calm. For exercise CO, measure during or immediately after activity.

Enter Stroke Volume

Input stroke volume in milliliters (mL) - the volume of blood ejected by the left ventricle per beat. This typically requires echocardiography or other medical imaging. Average resting stroke volume is 60-100 mL for adults, increasing with fitness level. If unknown, a medical professional can provide this measurement.

Calculate Cardiac Output

The calculator will compute your cardiac output (CO) by multiplying heart rate by stroke volume, typically displaying the result in liters per minute. It may also calculate cardiac index if you provide your height and weight for body surface area estimation.