Cardiac Output Calculator
Calculate cardiac output (CO) and cardiac index (CI) from stroke volume and heart rate. Cardiac output is the total volume of blood pumped by the heart per minute.
This free online cardiac output calculator provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Enter your values below and see results update in real time as you type. Perfect for everyday calculations, homework, or professional use.
Volume of blood per heartbeat
Body surface area for cardiac index
How to Use This Calculator
Enter your input values
Fill in all required input fields for the Cardiac Output Calculator. Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.
Review your inputs
Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.
Read the results
The Cardiac Output Calculator instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.
Explore parameter sensitivity
Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.
Formula Reference
Cardiac Output Calculator Formula
See calculator inputs for the governing equation
Variables: All variables and their units are labeled in the calculator interface above. Input fields accept values in multiple unit systems — select your preferred unit from the dropdown next to each field.
When to Use This Calculator
- •Use the Cardiac Output Calculator for personal health tracking and wellness monitoring, establishing a baseline and tracking changes over time.
- •Use it when recording fitness metrics to track progress toward health or athletic goals.
- •Use it to compare measurements before and after a lifestyle, diet, or training change to quantify the impact.
- •Use it as a conversation starter before a doctor's appointment, bringing objective data to discuss with a healthcare professional.
About This Calculator
The Cardiac Output Calculator is a free health and wellness calculation tool designed for personal use and general informational purposes. Calculate cardiac output (CO) and cardiac index (CI) from stroke volume and heart rate. Cardiac output is the total volume of blood pumped by the heart per minute. This calculator provides reference values based on established health screening formulas and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Results may vary based on individual factors not captured by the calculation. Consult a qualified healthcare provider for personalized health guidance. All calculations are performed locally in your browser — no personal health data is transmitted or stored.
About Cardiac Output Calculator
The Cardiac Output Calculator computes the total volume of blood the heart pumps per minute — the product of stroke volume and heart rate. Cardiac output is the single most important measure of overall cardiac performance and tissue perfusion. Normal resting CO is 4-8 L/min, increasing to 20-25 L/min during intense exercise. Cardiac index (CI) normalizes CO for body size using body surface area, allowing meaningful comparison between patients of different sizes. A CI below 2.2 L/min/m² indicates cardiogenic shock.
The Math Behind It
Formula Reference
Cardiac Output
CO = SV × HR / 1000
Variables: SV = stroke volume (mL), HR = heart rate (bpm), CO in L/min
Cardiac Index
CI = CO / BSA
Variables: BSA = body surface area (m²)
Worked Examples
Example 1: Normal Resting CO
SV 70 mL, HR 72 bpm, BSA 1.85 m²
CO 5.0 L/min, CI 2.7 L/min/m² — normal resting cardiac function.
Example 2: Heart Failure
SV 40 mL, HR 110 bpm, BSA 2.0 m²
CO 4.4 L/min, CI 2.2 L/min/m² — borderline shock despite compensatory tachycardia.
Example 3: Exercise
SV 130 mL, HR 170 bpm, BSA 1.9 m²
CO 22.1 L/min during intense exercise — 4x resting output.
Common Mistakes & Tips
- !Forgetting to divide by 1000 when converting from mL/min to L/min.
- !Interpreting CO without normalizing for body size. A CO of 4 L/min is normal for a small person but low for a large person. Use cardiac index instead.
- !Assuming high heart rate compensates for low stroke volume indefinitely. Tachycardia reduces diastolic filling time, eventually decreasing SV further.
Related Concepts
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Frequently Asked Questions
What is the difference between cardiac output and cardiac index?
Cardiac output (CO) is the total volume of blood pumped per minute (L/min). Cardiac index (CI) is CO divided by body surface area (L/min/m²), which normalizes for body size. CI is more clinically useful because it allows comparison between patients of different sizes.
What causes low cardiac output?
Heart failure (systolic dysfunction), severe bradycardia, hypovolemia (reduced preload), massive pulmonary embolism (right heart obstruction), cardiac tamponade (pericardial compression), and severe valvular disease are common causes.
How does exercise increase cardiac output?
Both HR and SV increase. HR rises from ~70 to 180+ bpm through sympathetic activation. SV increases from ~70 to 120-130 mL through increased venous return (preload), enhanced contractility, and reduced peripheral resistance.