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Cardiac Output Calculator

Enter heart rate and stroke volume to estimate cardiac output.

How it is calculated

The tool multiplies two numbers: CO (mL/min) = HR × SV, then divides by 1,000 to give CO (L/min). HR is the heart rate in beats per minute and SV is the stroke volume, the blood ejected by one beat, in millilitres. Both must be greater than zero or there is no result. The result is shown in L/min with two decimals and in whole mL/min. The stroke volume is something you must supply, from an echocardiogram or a monitor, for example; the tool does not estimate it from height, weight or age. It is an arithmetic estimate for study and checking, not a diagnosis.

Worked example

Take a resting heart rate of 72 beats per minute and a stroke volume of 70 mL. Step 1: 72 × 70 = 5,040 mL of blood per minute. Step 2: divide by 1,000 to convert to litres. The tool reports 5.04 L/min (5,040 mL/min). If the heart rate rose to 100 while the stroke volume stayed at 70, the output would be 7.00 L/min, which shows how much a faster pulse alone can raise the total.

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Common mistakes

  • Entering stroke volume in litres. A value like 0.07 is read as 0.07 mL and gives 0.01 L/min; the field expects millilitres, so write 70.
  • Confusing stroke volume with ejection fraction. The ejection fraction is a percentage (for example 60%), not a volume in millilitres per beat such as the 70 the tool needs.
  • Using a peak or exercise heart rate with a resting stroke volume. Both numbers must come from the same moment, because stroke volume also changes with activity.
  • Mixing up cardiac output with cardiac index. The tool does not divide by body surface area, so you cannot compare its figure with an index value in L/min/m².

Sources

About this calculator

Cardiac output (CO) is the volume of blood the heart pumps per minute, calculated with the simple relationship CO = heart rate × stroke volume, where stroke volume is the blood ejected per heartbeat (typically measured or estimated in mL and reported as CO in liters per minute). A healthy resting adult has a CO of roughly 4 to 8 L/min, though the value rises with exercise, fever, or pregnancy and falls in conditions like heart failure or shock.

Clinical methods such as the Fick principle and thermodilution measure cardiac output invasively, from oxygen uptake or a temperature curve; this calculator instead multiplies a heart rate by a stroke volume you supply. ICU and cardiac nurses, anesthesiologists, and cardiologists use cardiac output estimates to monitor how well a patient's circulation is meeting the body's demands during surgery, critical illness, or heart failure management.

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Comments (1)

  • Editorial team

    The tool only multiplies the two numbers you give it, so the quality of the result is the quality of your stroke volume, which usually comes from an echocardiogram or a monitor. The default 70 beats per minute at 70 mL gives 4.90 L/min. It is not scaled to body size, so it is not a cardiac index. This is for study and checking, and anything about a real patient belongs with a clinician. Where does your stroke volume come from?

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