Cardiac Output Calculator
Cardiac output is the total volume of blood your heart pumps per minute. It depends on two things: how fast the heart beats and how much blood it pushes out with each beat. Enter the heart rate and stroke volume to calculate CO, and optionally provide body surface area for the cardiac index.
Here's the formula:
Cardiac Output (L/min) = Heart Rate (bpm) x Stroke Volume (mL) / 1000
For a typical adult at rest with a heart rate of 72 bpm and a stroke volume of 70 mL, the cardiac output is about 5.0 L/min.
Normal ranges:
- Cardiac output (CO): 4.0-8.0 L/min at rest
- Cardiac index (CI): 2.2-4.0 L/min/m² (CO normalized for body size)
- Stroke volume: 60-100 mL per beat at rest
The cardiac index (CI = CO / BSA) is more clinically useful than raw CO because it adjusts for body size. A cardiac output of 4.5 L/min might be normal for a small person but inadequate for a large one.
When cardiac output drops:
- Below 4.0 L/min, tissues may not receive enough oxygen
- A cardiac index below 2.2 L/min/m² is one criterion for cardiogenic shock
- Heart failure, valve disease, and myocardial infarction can all reduce CO
When cardiac output is elevated:
- Sepsis, severe anemia, hyperthyroidism, and pregnancy all increase CO
- A cardiac index above 4.0 L/min/m² is considered a high-output state
- Exercise can temporarily increase CO to 20-25 L/min in trained athletes
In clinical practice, cardiac output is measured using thermodilution (Swan-Ganz catheter), echocardiography (Doppler), or arterial pulse contour analysis.