# Cardiac Index Calculator

URL: https://speedycalculator.com/calculators/health/cardiac-index/
Last updated: 2026-10-30

> The cardiac index calculator divides cardiac output by body surface area (Mosteller) to give a size-adjusted measure of heart pumping, and grades it as low, normal or high. It also shows the stroke volume index.

## Inputs

- Cardiac output (L/min)
- Heart rate (bpm)
- Height (cm, in, m, ft, mm)
- Weight (kg, lb, st, g)

## Results

- Body surface area
- Cardiac index
- Stroke volume index

## Formula

```
BSA = √(height cm × weight kg ÷ 3600)
CI = CO ÷ BSA
SVI = CI ÷ HR × 1000
```

## Explanation

A big person needs more blood flow than a small one, so cardiac output is often indexed to body surface area. A cardiac index below about 2.2 L/min/m² with signs of poor perfusion suggests cardiogenic shock.

### How to use the Cardiac Index Calculator

- **Cardiac output**
- **Heart rate**
- **Height**
- **Weight**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter cardiac output (from echo, thermodilution or the cardiac output calculator), heart rate, height and weight.

### Inputs explained

FieldWhat to enterCardiac outputIn L/minHeart rateIn bpmHeightUnits: cm, in, m, ft, mmWeightUnits: kg, lb, st, g

### What each result means

- **Body surface area** = sqrt([Height]×[Weight]÷3600)
- **Cardiac index** = [Cardiac output]÷[Body surface area]
- **Stroke volume index** = [Cardiac index]÷[Heart rate]×1000

### Example values

How the main result changes when **Cardiac output** changes and everything else stays at the example values above:

Cardiac output (L/min)Cardiac index (L/min/m²)2.751.444.132.165.52.886.883.68.254.32115.76
*Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.*

## Worked example

Inputs — Cardiac output: 5.5 L/min; Heart rate: 75 bpm; Height: 175 cm; Weight: 75 kg.

Results — Body surface area = 1.91 m²; **Cardiac index = 2.88 L/min/m²**; Stroke volume index = 38 mL/m².

## Key terms

- **CI**: Cardiac index.
- **SVI**: Stroke volume index.

## FAQ

**What is a normal cardiac index?**
About 2.5–4.0 L/min/m².

**What does a low cardiac index mean?**
The heart is not pumping enough blood for the body's size; it is a feature of cardiogenic shock.

**What is a normal stroke volume index?**
About 33–47 mL/m².


## Sources

- [Klabunde RE. Cardiovascular Physiology Concepts](https://cvphysiology.com/)