Cardiac Output Calculator

What Is Cardiac Output?

Cardiac output (CO) is the volume of blood the heart pumps each minute. It reflects overall circulatory performance and is central to hemodynamic assessment in cardiology and critical care. Related tools: Cardiac Index Calculator, Body Surface Area Calculator, and Blood Pressure Calculator.

Fick Equation

The Fick principle relates oxygen consumption to arteriovenous oxygen difference.

$$\text{CO} = \frac{VO_2}{C_a - C_v}$$

$VO_2$ is oxygen consumption in mL/min. $C_a$ and $C_v$ are arterial and venous oxygen content in mL/L, derived from hemoglobin, oxygen saturation, and partial pressure. When $VO_2$ is not measured directly, many calculators estimate $125 \text{ mL/min/m}^2$ multiplied by body surface area.

Normal Range

In resting adults, cardiac output is often cited between 4 and 8 L/min. Values outside this range may reflect low-output states, sepsis, anemia, or high metabolic demand. Cardiac index normalizes output to body size and is often more useful across patients of different stature.

Clinical Use

Direct Fick cardiac output requires invasive sampling and is most common in catheterization labs and intensive care. Noninvasive estimates exist, but this tool applies the classic content-based Fick method for educational and bedside estimation when the required inputs are available.