cardiac output calculator

Use heart rate and stroke volume to estimate cardiac output at rest or during activity.

Cardiac Output (L/min) = Heart Rate (beats/min) × Stroke Volume (mL/beat) ÷ 1000

What Is Cardiac Output?

Cardiac output is the amount of blood your heart pumps each minute. It is one of the most useful measurements for understanding circulation and overall cardiovascular performance. In simple terms, it tells you how effectively the heart is supplying oxygen-rich blood to tissues.

In physiology and clinical practice, cardiac output is commonly expressed in liters per minute (L/min). A resting adult often falls near 4 to 8 L/min, though normal values vary by body size, fitness, stress level, and health conditions.

Cardiac Output Formula

Core Equation

The standard equation is:

CO = HR × SV

CO = Cardiac Output (mL/min or L/min)
HR = Heart Rate (beats per minute)
SV = Stroke Volume (mL per beat)

Since heart rate is measured in beats/min and stroke volume in mL/beat, multiplying them gives mL/min. Divide by 1000 to convert to L/min.

Example

If heart rate is 75 bpm and stroke volume is 70 mL/beat:

CO = 75 × 70 = 5250 mL/min
CO = 5.25 L/min

Cardiac Output vs Cardiac Index

Cardiac output is useful, but larger people naturally tend to have higher values. To account for body size, clinicians often use cardiac index (CI):

Cardiac Index (L/min/m²) = Cardiac Output (L/min) ÷ Body Surface Area (m²)

This calculator optionally computes cardiac index if you enter body surface area. Typical resting cardiac index often falls around 2.5 to 4.0 L/min/m².

Reference Ranges (General Guide)

Measurement	Common Resting Range (Adults)
Cardiac Output	~4.0 to 8.0 L/min
Cardiac Index	~2.5 to 4.0 L/min/m²
Heart Rate	~60 to 100 beats/min
Stroke Volume	~60 to 100 mL/beat (varies widely)

What Affects Cardiac Output?

Heart rate: Faster rate can raise output up to a point.
Stroke volume: More blood ejected per beat increases output.
Hydration and blood volume: Dehydration can lower preload and stroke volume.
Fitness level: Trained individuals may have higher stroke volume at rest.
Medications and disease: Beta-blockers, heart failure, arrhythmias, and valve disease can affect output.

How to Use This Calculator Correctly

Measure or estimate resting heart rate (bpm).
Use a realistic stroke volume estimate (mL/beat).
Enter body surface area if you want cardiac index.
Interpret results with context: posture, stress, exercise, and medications all matter.

For non-invasive fitness tracking, trends over time are usually more valuable than a single isolated number.

Important Note

This tool is for education and general estimation only. It does not diagnose disease and is not a substitute for professional medical evaluation. If you have symptoms like chest pain, breathlessness, fainting, swelling, or unusual fatigue, consult a qualified clinician.