Cardiac Output Calculator
Enter heart rate and stroke volume to estimate cardiac output in L/min and mL/min. Optionally add body surface area to compute cardiac index. See a CO gauge against published reference zones and a full step-by-step breakdown. For physiology study and educational use only — not a clinical diagnostic tool.
Quick preset
Hemodynamic inputs
Body surface area (optional)
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Step-by-step
What this calculator does
This cardiac output calculator multiplies heart rate (beats/min) by stroke volume (mL/beat) to estimate cardiac output in mL/min and L/min. If body surface area is provided, it also computes cardiac index by dividing CO by BSA — a body-size-adjusted measure commonly discussed in physiology and hemodynamics education.
The CO gauge positions the calculated result against a commonly cited reference range for resting adults (approximately 4–8 L/min). The gauge is for educational illustration only — published reference ranges vary by source, population, age, activity level, and measurement method.
Formulas used
CO (mL/min) = HR (bpm) × SV (mL/beat)
CO (L/min) = CO (mL/min) ÷ 1000
Cardiac Index (CI) = CO (L/min) ÷ Body Surface Area (m²)
CI units: L/min/m²
Example (default preset):
CO = 72 × 70 = 5,040 mL/min = 5.040 L/min
CI = 5.040 ÷ 1.9 = 2.653 L/min/m²
Published reference ranges (educational)
Reference ranges above are general educational values from physiology literature. Actual normal ranges depend on age, sex, body habitus, activity level, clinical context, and measurement method. These values do not constitute diagnostic thresholds.
How to use
- Select a preset or enter your own heart rate (bpm) and stroke volume (mL/beat).
- Optionally add body surface area (m²) to also compute cardiac index. Leave at 0 to skip CI.
- Click Calculate — the gauge shows where CO falls relative to the commonly cited 4–8 L/min reference zone.
- Use the step-by-step panel to review the arithmetic for coursework or study reference.
FAQ
What is cardiac output?
Cardiac output is the volume of blood the heart pumps per minute, calculated as heart rate multiplied by stroke volume. At rest in a typical adult, cardiac output is approximately 4–8 liters per minute. During vigorous exercise, cardiac output can increase to 20–25 L/min or more in trained athletes, primarily driven by increases in both heart rate and stroke volume.
What is stroke volume?
Stroke volume is the amount of blood ejected from the left ventricle with each heartbeat, expressed in milliliters per beat. At rest, stroke volume typically ranges from 60–100 mL/beat in adults. It is determined by preload (ventricular filling), afterload (resistance to ejection), and myocardial contractility.
What is cardiac index and why is it used?
Cardiac index adjusts cardiac output for body surface area (CI = CO ÷ BSA). A larger person generally needs a higher absolute cardiac output to perfuse their body, so comparing CO directly between individuals of different sizes can be misleading. Cardiac index normalizes for body size, making comparisons more meaningful in physiology and hemodynamic education. A commonly cited normal CI range is approximately 2.2–4.0 L/min/m².
Is a higher cardiac output always better?
No. Both low and high cardiac output can reflect physiological or pathological states. Low CO may occur with heart failure, hypovolemia, or severe bradycardia. Elevated CO occurs normally during exercise, fever, anxiety, and pregnancy. Very high CO at rest can also reflect pathological states. The clinical significance of any CO value depends entirely on context, symptoms, and other hemodynamic parameters — not the number alone.
How is cardiac output actually measured clinically?
In clinical settings, cardiac output is measured using validated methods including thermodilution via pulmonary artery catheter, the Fick oxygen consumption method, Doppler echocardiography, arterial pulse contour analysis, and various non-invasive cardiac monitoring systems. Each method has specific indications, limitations, and accuracy considerations. This calculator performs arithmetic only — it does not replicate any measurement method.
Can this tool be used for clinical decisions?
No. This tool performs arithmetic on values entered by the user and provides educational reference context. It does not measure cardiac output, assess cardiovascular function, or account for clinical context. Any cardiac output value relevant to patient care must be obtained through validated clinical measurement methods and interpreted by qualified medical professionals within the full clinical picture.
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Important disclaimer
This tool is for educational and physiology study purposes only. It performs arithmetic on values entered by the user and displays the result alongside general reference information from physiology literature. It does not measure, monitor, assess, or diagnose any aspect of cardiovascular function.
Reference ranges shown in this tool are general educational values from published physiology literature. They are not diagnostic thresholds and must not be applied to individual patients. Normal cardiac output varies significantly with age, sex, body size, activity level, physiological state, and clinical context.
GentoolLab is not a medical provider. Nothing on this page constitutes medical advice, clinical guidance, hemodynamic monitoring, or a substitute for qualified professional evaluation. If you have concerns about cardiovascular health or function, consult a qualified healthcare professional.
See also: GentoolLab full disclaimer.