Cardiac Output Calculator

Human Physiology • Cardiovascular Physiology

Written by STEM Calculators Team Published April 13, 2026 Updated April 13, 2026

Cardiac output calculator

Compute cardiac output from heart rate and stroke volume, optionally normalize to cardiac index with body surface area, compare two states, and inspect flow visually with interactive charts.

Quick comparison preset

Compare two physiological states Include cardiac index using body surface area

Teaching ranges used here are approximate: low cardiac output < 4.00 L/min, normal about 4.00–8.00 L/min, elevated > 8.00 L/min.

State A

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Stroke volume unit

Heart rate

Stroke volume

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Optional columns: label,hr,sv,svUnit,bsa. Use one or two rows. Example svUnit values: mL or L.

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Cardiac output and blood flow per minute

A cardiac output calculator estimates the total volume of blood pumped by the heart each minute. The main computed quantity is cardiac output, and the same inputs can also support cardiac index when body surface area is included.

Cardiac output depends on two core variables: heart rate and stroke volume. Because it combines how often the heart beats with how much blood is ejected per beat, cardiac output is one of the clearest ways to describe overall pump performance in cardiovascular physiology.

Core definitions and formulas

Heart rate is usually measured in beats per minute, and stroke volume is usually measured in mL per beat. Cardiac output is their product. When body surface area is available, cardiac index normalizes cardiac output to body size.

\[ \begin{aligned} CO &= HR \cdot SV \end{aligned} \] \[ \begin{aligned} CO_{\text{L/min}} &= \frac{CO_{\text{mL/min}}}{1000} \end{aligned} \] \[ \begin{aligned} CI &= \frac{CO}{BSA} \end{aligned} \]

Here, \(CO\) is cardiac output, \(HR\) is heart rate, \(SV\) is stroke volume, \(CI\) is cardiac index, and \(BSA\) is body surface area. If stroke volume is entered in liters per beat, it should be converted before interpretation so the final flow units remain consistent.

How to interpret results

A larger cardiac output means the heart is delivering more blood to the circulation each minute. This often occurs during exercise, when both heart rate and stroke volume may rise. A smaller cardiac output suggests reduced flow delivery and may reflect a slower heart rate, a lower stroke volume, or reduced pump function.

Common units are L/min for cardiac output and L/min/m² for cardiac index. In comparison mode, the main question is whether the change comes mostly from heart rate, stroke volume, or both. Cardiac index is especially useful when comparing people of different body sizes because it adjusts flow for body surface area.

Common pitfalls

Mixing mL and L for stroke volume without converting correctly.
Assuming a high heart rate always means high cardiac output.
Ignoring low stroke volume when interpreting reduced flow.
Using cardiac output alone when body-size normalization is needed.

Micro example: if \(HR = 72\) bpm and \(SV = 70\) mL/beat, then \(CO = 72 \cdot 70 = 5040\) mL/min, which is \(5.04\) L/min. If \(BSA = 1.90\) m², then \(CI = 5.04 / 1.90 \approx 2.65\) L/min/m².

This tool is useful for basic hemodynamics, exercise physiology, and introductory cardiovascular interpretation. It is not meant to replace full clinical assessment; the next step for deeper analysis is often stroke volume, arterial pressure, resistance, venous return, or pressure-volume relationships.

Frequently Asked Questions

What does a cardiac output calculator measure?

It calculates the total volume of blood pumped by the heart each minute. The result is based on heart rate and stroke volume.

How is cardiac output calculated?

Cardiac output is calculated with the formula CO = HR x SV. If heart rate is 72 bpm and stroke volume is 70 mL/beat, cardiac output is 5040 mL/min or 5.04 L/min.

What is the difference between cardiac output and cardiac index?

Cardiac output is the total blood flow per minute, usually in L/min. Cardiac index is cardiac output divided by body surface area, which adjusts the value for body size.

Why can cardiac output change even if heart rate stays the same?

Cardiac output depends on both heart rate and stroke volume. If stroke volume rises or falls while heart rate stays constant, total flow per minute will still change.

When is comparison mode useful in a cardiac output calculator?

Comparison mode is useful for examining differences between physiological states such as rest and exercise or normal versus reduced pump function. It helps show whether total flow increases or decreases and by how much.

Cardiac Output Calculator

State A

State B

Paste or import CSV data

Calculation steps

Flow-per-minute bar chart

Heart rate × stroke volume relationship

Comparison column chart

Flow arrows from heart to circulation

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Frequently Asked Questions

State A

State B

Paste or import CSV data

Calculation steps

Flow-per-minute bar chart

Heart rate × stroke volume relationship

Comparison column chart

Flow arrows from heart to circulation

Rate this calculator

Frequently Asked Questions

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