Home›Calculators›Health›Cardiac Index Calculator

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.

Reviewed by the thecalcu.com team · Last updated July 30, 2026

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.

Why Use a Cardiac Index Calculator?

Cardiac output alone can be misleading when comparing patients of different sizes, a cardiac output that's perfectly adequate for a small adult might be insufficient for a much larger one. Cardiac index solves this by normalizing to body surface area, giving a single number that can be checked against the same 2.5–4.0 L/min/m² reference range regardless of patient size.

This is useful for nursing and allied health students learning hemodynamic monitoring concepts, or anyone who has stroke volume and heart rate figures from an echocardiogram or hemodynamic monitor and wants to quickly see how those numbers translate into the standard cardiac index used in critical care.

Who Should Use This Calculator?

Nursing, paramedic, and allied health students studying hemodynamics can use this tool to see how cardiac index is derived step by step from its component measurements. Critical care and cardiology trainees preparing for exams that cover hemodynamic monitoring will find it useful for checking worked examples against the standard formula.

Patients or caregivers who have received a stroke volume measurement from an echocardiogram and want to understand what it means in the context of overall cardiac function can also use this tool for general education. This calculator is for informational and educational purposes only and does not replace the clinical monitoring and interpretation provided by a treating physician or intensive care team.

What Insights Does the Cardiac Index Calculator Give You?

Cardiac Index is the primary result, your cardiac output divided by body surface area, in L/min/m². This is the figure most directly comparable to the standard clinical reference range.

Cardiac Output shows the intermediate result of heart rate multiplied by stroke volume, in liters per minute, before the body-size adjustment is applied. Body Surface Area shows the Mosteller-formula BSA calculated from your height and weight inputs, in square meters. Normal Range Check flags whether your cardiac index falls below, within, or above the standard 2.5–4.0 L/min/m² reference range, giving quick context for what the number means.

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.
Show formula & methodology ↓Show less ↑

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

What is cardiac index and how is it different from cardiac output?
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.
What is a normal cardiac index?
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.
How is body surface area calculated in this tool?
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).
What does a low cardiac index indicate?
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.
What does a high cardiac index indicate?
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.
How do I find my stroke volume to use this calculator?
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.
Can I use this calculator instead of a formal hemodynamic assessment?
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.
Why does cardiac index matter more than cardiac output in the ICU?
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.
How does heart rate affect cardiac index?
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.
What is the difference between the Mosteller and DuBois BSA formulas?
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.
How is cardiac index related to the Cardiac Output Calculator?
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