Cardiac Output Calculator (heart rate × stroke volume)

Understanding the cardiac output calculator — concept and principle

This calculator works out cardiac output, the volume of blood the heart pumps each minute, from heart rate and stroke volume. With body surface area it also gives the cardiac index, and it shows how much blood is pumped per hour and per day at that rate. Students of physiology, nurses and fitness enthusiasts use it.

Beats × volume per beat — with the default inputs: 5.04 L/min.

How it is calculated

Cardiac output CO (L/min) = heart rate (beats/min) × stroke volume (mL/beat) ÷ 1,000
Cardiac index = CO ÷ body surface area (m²)
Per hour = CO × 60; per day = CO × 1,440
Usual resting adult range: CO 4–8 L/min; stroke volume 60–100 mL; CI 2.5–4.0 L/min/m²

The principle

Each heartbeat ejects a stroke volume of blood; multiplying by the number of beats per minute gives the flow per minute. The body adjusts cardiac output by changing either term: during exercise both heart rate and stroke volume rise, and output can increase four- to six-fold. Dividing by body surface area gives the cardiac index for comparison between people of different sizes.

Worked example

Defaults: heart rate 72, stroke volume 70 mL, BSA 1.9 m².

CO = 72 × 70 ÷ 1,000 = 5.04 L/min: Within the usual range.
Cardiac index = 5.04 ÷ 1.9 = 2.65 L/min/m².
Per hour = 5.04 × 60 = 302 L; per day = 5.04 × 1,440 = 7,258 L.

Each point is the calculator re-run with only “Heart rate (bpm)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Heart rate (bpm)	Cardiac output (L/min)
18	1.26
36	2.52
54	3.78
72	5.04
90	6.3
108	7.56
144	10.08

How to read the result

Where does your result fall?

A resting output of about 5 L/min means the whole blood volume circulates roughly once a minute. The hour and day totals assume the resting rate all day; real output changes with activity, posture, temperature and digestion. In clinical settings cardiac output is measured with specialised methods and read with blood pressure and other signs.

Common mistakes

Entering stroke volume in litres instead of millilitres.
Comparing exercise values with resting ranges.
Assuming a high heart rate always means high output; very fast rates can reduce stroke volume.
Treating the daily total as precise.

Keep in mind: Not a diagnosis. Heart function is assessed by clinicians with proper measurements.

Frequently asked questions

What is a normal cardiac output?

About 4–8 L/min at rest in adults.

How much blood does the heart pump a day?

About 7,000 L at a resting output of 5 L/min.

How does exercise change cardiac output?

Heart rate and stroke volume both rise, so output can increase several-fold.

Sources: Edwards Lifesciences Clinical Education, "Normal Haemodynamic Parameters and Laboratory Values" (2022)

Checked 9 Nov 2026. Edwards Lifesciences Clinical Education, “Normal Haemodynamic Parameters and Laboratory Values” (2022, PP--EU-4269 v1.0): CO = HR × SV/1000, 4–8 L/min; SV 60–100 mL/beat; CI 2.5–4 L/min/m².

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