Cardiac output is the volume of blood one ventricle pumps in one minute. It equals stroke volume (blood pumped per heartbeat, about 70 mL) multiplied by heart rate (beats per minute, about 72). So a normal adult has a cardiac output of about 5000 mL, that is 5 litres per minute. Memory hook: CO = SV x HR, and 70 x 72 is roughly 5000, so "one heart, five litres a minute".
Cardiac output equals stroke volume multiplied by heart rate. Normal values (~70 mL x ~72/min) give about 5 litres per minute. Stroke volume itself is the end-diastolic minus end-systolic volume.
Your doubts, answered
Is cardiac output measured per beat or per minute?
Per minute. Stroke volume is the amount pumped in one beat (about 70 mL). Cardiac output is the amount pumped in one full minute. You get it by multiplying stroke volume by how many beats happen in that minute (heart rate).
What is the difference between stroke volume and cardiac output?
Stroke volume is the blood one ventricle pushes out in a single heartbeat (~70 mL). Cardiac output is the total blood pumped in one minute (~5000 mL). Cardiac output = stroke volume x heart rate. So stroke volume is one beat, cardiac output is one minute.
How do I find stroke volume from end-diastolic and end-systolic volume?
Stroke volume = end-diastolic volume minus end-systolic volume. The ventricle fills to its fullest at the end of diastole and empties partly during systole. The difference is what actually left the heart. Example: 100 mL - 50 mL = 50 mL stroke volume.
Why is normal cardiac output about 5 litres per minute?
Because a normal stroke volume of about 70 mL is multiplied by a normal heart rate of about 72 beats per minute. 70 x 72 is about 5040 mL, which NCERT rounds to about 5000 mL, that is 5 litres per minute.
Does cardiac output count both ventricles together?
No. Cardiac output is measured for one ventricle. Both ventricles pump the same volume in the same time, so their outputs are equal. NCERT states the cardiac output of a healthy person is about 5000 mL per minute, meaning per ventricle.
⚠️ The NEET trap ✗ Treating cardiac output (per minute) as if it were stroke volume (per beat), or forgetting to subtract end-systolic volume, so stroke volume is taken as the full 100 mL instead of the 50 mL that actually left. ✓ Stroke volume = end-diastolic - end-systolic volume. Then heart rate = cardiac output / stroke volume. Keep cardiac output in mL (5 L = 5000 mL) so units match before dividing. 🧠 Read the units before you multiply or divide.
Real NEET questions
2019
What would be the heart rate of a person if the cardiac output is 5 L, blood volume in the ventricles at the end of diastole is 100 mL and at the end of ventricular systole is 50 mL?
A · 50 beats per minute
B · 75 beats per minute
C · 100 beats per minute ✓
D · 125 beats per minute
Solution: Stroke volume = end-diastolic volume - end-systolic volume = 100 - 50 = 50 mL. Cardiac output = stroke volume x heart rate, so heart rate = cardiac output / stroke volume = 5000 mL / 50 mL = 100 beats per minute.
2026
The number of action potentials generated by the sino-atrial node (SAN) in a healthy human is _______ per minute.
A · 28 - 30
B · 70 - 75 ✓
C · 100 - 110
D · 120 - 140
Solution: The SA node is the pacemaker and sets the resting heart rate. It fires about 70-75 action potentials per minute, giving the normal resting heart rate of about 72 beats per minute, which drives a cardiac output near 5 litres per minute.
Solved Body Fluids and Circulation NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Cardiac output = stroke volume x heart rate (CO = SV x HR). With SV about 70 mL and HR about 72 per minute, CO is about 5000 mL (5 L) per minute.
What is a normal stroke volume?
About 70 mL of blood pumped by one ventricle in a single heartbeat, as given in NCERT.
What is the normal cardiac output of a healthy person?
About 5000 mL, that is 5 litres, of blood per minute at rest.
How does the body increase cardiac output during exercise?
By raising heart rate and stroke volume. Sympathetic nerves and adrenal medullary hormones (adrenaline) increase the rate and force of contraction, so more blood is pumped per minute.
Why is knowing CO = SV x HR important for NEET?
NEET repeatedly asks numerical questions where you find one value from the other two, like the 2019 heart-rate question. The formula and the difference of ventricular volumes are direct one-mark scorers.
