Heart rate, stroke volume and cardiac output

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Heart rate, stroke volume and cardiac outputSpec 8.12

In short

Cardiac output is the volume of blood pumped out of the heart per minute, in cm³ per minute. It is calculated as cardiac output = stroke volume × heart rate, where stroke volume is the volume pumped in each beat and heart rate is beats per minute. For example, 75 cm³ × 70 bpm = 5250 cm³ per minute.

Heart rate: The number of times the heart beats per minute (bpm).
Stroke volume: The volume of blood pumped out of the heart in each beat, in cm³.
Cardiac output: The volume of blood pumped out of the heart per minute, in cm³ per minute.

cardiac output = stroke volume × heart rate

Calculating cardiac output

A person has a resting heart rate of 70 beats per minute and a stroke volume of 75 cm³. Calculate the cardiac output.

cardiac output = stroke volume × heart rate
cardiac output = 75 × 70 = 5250

Answer: 5250 cm³ per minute

You may be asked to rearrange the equation. Stroke volume = cardiac output ÷ heart rate. Heart rate = cardiac output ÷ stroke volume.

You can measure heart rate by taking a pulse for a set time, for example counting beats in 30 seconds and doubling. A suggested practical is to investigate the short-term effect of exercise on heart rate and breathing rate, which both increase to supply more oxygen to the working muscles.

Maths skill:

Check the units. If a question gives heart rate in beats per minute and stroke volume in cm³, the answer is in cm³ per minute. Give the unit in your answer.

Quick check

Which vessel carries oxygenated blood from the lungs to the heart?
Show answer
The pulmonary vein.
Why is the wall of the left ventricle thicker than the wall of the right ventricle?
Show answer
It pumps blood around the whole body, which needs a higher pressure than pumping blood to the lungs.
What is the job of the valves in the heart?
Show answer
To prevent backflow and keep blood flowing in one direction.
State the equation for cardiac output.
Show answer
Cardiac output = stroke volume × heart rate.

Written and checked against the Edexcel GCSE Biology (1BI0) specification · Updated October 2026

Frequently asked questions

How does the heart pump blood?

Deoxygenated blood enters the right atrium through the vena cava. The right atrium contracts, pushing blood into the right ventricle, which pumps it to the lungs through the pulmonary artery. Oxygenated blood returns through the pulmonary vein to the left atrium, then the left ventricle pumps it around the body through the aorta. Valves prevent backflow.

Why is the left ventricle thicker than the right?

The left ventricle has a thicker, more muscular wall because it pumps blood around the whole body, which needs a higher pressure. The right ventricle pumps blood only to the lungs, which are close by. The higher pressure matters because blood pressure falls as blood passes through the capillaries in the lungs.

What blood vessels carry blood away from the heart?

Arteries carry blood away from the heart. The aorta carries oxygenated blood from the left ventricle to the body, and the pulmonary artery carries deoxygenated blood from the right ventricle to the lungs. So not all arteries carry oxygenated blood: the pulmonary artery is the exception. Veins carry blood towards the heart.

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