Calculate cardiac index, cardiac output, and stroke volume index from heart rate, stroke volume, and body surface area. Classifies hemodynamic status.
The Cardiac Index Calculator computes cardiac output (CO), cardiac index (CI), and stroke volume index (SI) from heart rate, stroke volume, and body surface area. Normalizing output to body size makes the numbers easier to compare across patients.
Cardiac index is commonly used in critical care, cardiology, and perioperative medicine. Typical CI values are about 2.2 to 4.0 L/min/m², with values below 1.8 suggesting low output and very high values pointing toward a hyperdynamic state.
The calculator also reports systemic vascular resistance when MAP and CVP are available, so you can see whether a low CI is more consistent with poor pump function, low preload, or reduced vascular tone.
Cardiac output alone can be misleading because it does not account for body size. A value that is acceptable for one patient may be inadequate for another.
CI helps clinicians compare perfusion targets, assess shock states, and follow hemodynamic trends after fluids, vasopressors, or inotropes.
CO = HR × SV / 1000 (L/min) BSA = √(Height × Weight / 3600) [Mosteller] CI = CO / BSA (L/min/m²) SI = SV / BSA (mL/m²) SVR = 80 × (MAP - CVP) / CO (dyn·s/cm⁵)
Result: CI 2.61 L/min/m² — Normal
CO = 72 × 70 / 1000 = 5.04 L/min. BSA = √(175 × 75 / 3600) = 1.93 m². CI = 5.04 / 1.93 = 2.61 L/min/m², which is within the normal range (2.2-4.0).
The cardiac index is one part of hemodynamic assessment. It is often interpreted alongside preload, afterload, and contractility to help explain why perfusion is low or high.
When the cardiac index improves after a fluid challenge, it can suggest that the patient is preload responsive. That makes serial measurements more useful than a single snapshot.
A low CI can reflect poor pump function, low circulating volume, or excessive afterload. A high CI can appear in pregnancy, exercise, sepsis, anemia, or other high-output states.
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This calculator defines cardiac index in the standard way as cardiac output divided by body surface area, with optional derived values such as stroke-volume index and an estimated SVR layer for context. The page is most useful as a quick normalization tool when the user already has a stroke-volume estimate from echocardiography or another hemodynamic method.
The output should not be treated as a universal invasive hemodynamic measurement. Reference ranges vary with how cardiac output and stroke volume were obtained, and any SVR estimate built from assumed MAP or CVP values is only a rough orientation aid rather than a formal bedside hemodynamic diagnosis.
Cardiac output (CO) is the total volume of blood pumped by the heart per minute (L/min). Cardiac index (CI) normalizes CO to body surface area (L/min/m²), allowing comparison across patients of different sizes. CI is the preferred clinical parameter.
Stroke volume can be measured by echocardiography (LVOT VTI method), pulmonary artery catheter (thermodilution), arterial waveform analysis (FloTrac, PiCCO), or estimated from biometric data. Echo-derived SV is the most common non-invasive method.
Low CI can result from reduced contractility (heart failure, MI), inadequate preload (hypovolemia, tamponade), excessive afterload (aortic stenosis, hypertension), or arrhythmias. The treatment depends on the underlying cause.
CI >4.0 can be physiologic (exercise, pregnancy) or pathologic (sepsis, anemia, thyrotoxicosis, AV fistula, liver cirrhosis). High-output states often have low SVR and may still cause organ hypoperfusion in distributive shock.
BSA better reflects metabolic rate and oxygen consumption than weight alone. Since cardiac output exists to meet metabolic demands, normalizing to BSA provides a more physiologically meaningful index of cardiac performance adequacy.
The Du Bois formula may be less accurate in obese patients, children, or those with extremes of body habitus. Alternative formulas (Mosteller, Haycock) exist for specific populations. For clinical CI calculations, the differences are generally small.