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Cardiac Index Calculator

Health

Calculate cardiac index from heart rate, stroke volume, height, and weight using the Mosteller body surface area formula, with the normal 2.5-4.0 range shown.

Heart Rate
bpm
Stroke Volume
mL
Height
cm
Weight
kg

Cardiac Index

0L/min/m²

Normal Range: 2.5-4.0

—

Cardiac Output0 L/min
Body Surface Area0 m²

Not a substitute for clinical monitoring. Cardiac index should be interpreted alongside other hemodynamic data by a qualified healthcare provider.

What is a Cardiac Index?

The Cardiac Index Calculator estimates cardiac index — a body-size-adjusted measure of how much blood the heart pumps each minute — from heart rate, stroke volume, height, and weight. Cardiac index is calculated as cardiac output divided by body surface area (BSA), giving a value in liters per minute per square meter (L/min/m²) that clinicians use to assess whether the heart is meeting the body's circulatory demands.

This tool first computes cardiac output (heart rate × stroke volume), then calculates body surface area using the Mosteller formula, and finally divides the two to produce the cardiac index alongside a normal-range check. For a related hemodynamic figure without the body-size adjustment, see the Cardiac Output Calculator; for the body surface area value on its own, see the Body Surface Area Calculator.

How to use this Cardiac Index calculator

  1. Enter your Heart Rate in beats per minute.
  2. Enter your Stroke Volume in milliliters — this value typically comes from an echocardiogram or hemodynamic monitor.
  3. Enter your Height in centimeters.
  4. Enter your Weight in kilograms.
  5. Review the Cardiac Index result along with the intermediate Cardiac Output and Body Surface Area values, and check the Normal Range Check label to see whether the result falls within the standard 2.5–4.0 L/min/m² range.

Formula & Methodology

Cardiac output is calculated as:

CO (L/min) = (Heart Rate × Stroke Volume) ÷ 1000

Body surface area uses the Mosteller formula:

BSA (m²) = √(Height(cm) × Weight(kg) ÷ 3600)

Cardiac index is then:

CI (L/min/m²) = CO ÷ BSA

Worked example: For a heart rate of 70 bpm, stroke volume of 70 mL, height of 170 cm, and weight of 75 kg: CO = (70 × 70) ÷ 1000 = 4.9 L/min. BSA = √(170 × 75 ÷ 3600) = √3.542 = 1.882 m². CI = 4.9 ÷ 1.882 = 2.60 L/min/m², which falls within the normal 2.5–4.0 range.

Frequently Asked Questions

Cardiac index is cardiac output divided by body surface area, expressed in liters per minute per square meter (L/min/m²). Cardiac output alone tells you the total blood volume the heart pumps each minute, but it doesn't account for body size — cardiac index normalizes that figure so a small adult and a large adult can be compared on the same scale.
A normal resting cardiac index for an adult falls between approximately 2.5 and 4.0 L/min/m². Values below this range suggest the heart may not be pumping enough blood relative to body size, while values above it can reflect a hyperdynamic state such as fever, sepsis, or anemia.
This calculator uses the Mosteller formula, BSA = √(height in cm × weight in kg ÷ 3600), which is the most widely used clinical BSA equation because of its simplicity and accuracy across a broad range of body sizes. The result is expressed in square meters (m²).
A cardiac index below 2.5 L/min/m² can indicate cardiogenic shock, heart failure, or reduced stroke volume, and is a key threshold clinicians use when assessing hemodynamic stability in critical care settings. A low cardiac index alone doesn't diagnose a specific condition — it must be interpreted alongside blood pressure, heart rhythm, and other vital signs.
A cardiac index above 4.0 L/min/m² is sometimes seen in hyperdynamic states such as sepsis, severe anemia, hyperthyroidism, or significant fever, where the body compensates by increasing heart rate or stroke volume. It can also occur transiently during exercise or acute stress.
Stroke volume is typically measured via echocardiography, cardiac MRI, or invasive hemodynamic monitoring (such as a pulmonary artery catheter), and is reported directly by the clinician or diagnostic report performing that test. This calculator does not estimate stroke volume from other measurements — you'll need this value from a prior test or monitoring device.
No — this calculator is intended for informational and educational purposes only, to help you understand what the cardiac index formula produces from known inputs. It is not a substitute for professional medical evaluation, and treatment decisions in cardiac or critical care should always be made by a qualified healthcare provider using validated clinical monitoring.
In intensive care, patients vary widely in body size, so a cardiac output of 5 L/min might be adequate for a smaller patient but insufficient for a larger one. Indexing to body surface area lets clinicians apply the same 2.5–4.0 L/min/m² reference range across patients of different sizes.
Since cardiac output equals heart rate multiplied by stroke volume, an increase in heart rate raises cardiac output — and therefore cardiac index — as long as stroke volume doesn't fall proportionally. In some conditions, very fast heart rates actually reduce stroke volume enough that cardiac output falls despite the higher rate.
The Mosteller formula used here is a simpler square-root-based equation, while the DuBois formula uses height and weight raised to specific exponents derived from an older study. Both produce very similar BSA estimates for most adults, and Mosteller is now the more commonly used formula in clinical practice due to its ease of calculation.
The [Cardiac Output Calculator](/cardiac-output-calculator/) computes the same heart-rate-times-stroke-volume result shown here, but without dividing by body surface area. Use that calculator if you only need the raw cardiac output figure, or this one if you need the body-size-adjusted index for comparison against standard clinical thresholds.
Also known as
CI calculatorcardiac index formula calculatorcardiac index normal range checkercardiac output body surface area calculatorhemodynamic cardiac index calculator