Cardiac Index Calculator
Calculate cardiac index (CI) — cardiac output adjusted for body size. Enter cardiac output and body surface area, and this calculator divides one by the other to give CI in L/min/m², along with where it sits relative to the normal range.
Rates and fees change frequently. Always confirm the current figures
with the official authority before relying on this result.
- Educational estimate. Clinical interpretation requires professional assessment.
Formula
Cardiac Index = Cardiac Output ÷ Body Surface Area
- Cardiac index normalises cardiac output to body size so values are comparable between people.
- CI = cardiac output (L/min) ÷ body surface area (m²).
- The normal resting range is about 2.5–4.0 L/min/m².
- Low CI can reflect reduced pump function; high CI points to a high-output state (e.g. sepsis, anaemia).
- Find body surface area with a BSA calculator (e.g. the Mosteller formula) from height and weight.
- This is an educational estimate; clinical interpretation needs a professional.
CO 5 L/min, BSA 1.8 m²
Inputs
- Cardiac output: 5 L/min
- Body surface area: 1.8 m²
Cardiac index = 5 ÷ 1.8 ≈ 2.78 L/min/m², which sits within the normal 2.5–4.0 range.
Frequently asked questions
What is cardiac index?
It's cardiac output divided by body surface area, giving heart output per square metre of body. This lets clinicians compare heart performance across people of different sizes.
What is a normal cardiac index?
At rest, roughly 2.5–4.0 L/min/m². Below this may indicate reduced heart function; above it suggests a high-output state.
How do I get body surface area?
Use a BSA calculator with your height and weight. The Mosteller and Du Bois formulas are common; the result feeds directly into this calculation.
Why use cardiac index instead of cardiac output?
A 5 L/min output means very different things for a small versus a large person. Indexing to body surface area makes the value meaningful across body sizes.
Related calculators
Cardiac Output Calculator Calculate cardiac output — the volume of blood your heart pumps each minute. Enter heart rate and stroke volume, and this calculator multiplies them (and converts to litres) to give cardiac output in L/min, with how it compares to the normal resting range. Body Surface Area (BSA) Calculator Calculate your body surface area (BSA) with the Mosteller and Du Bois formulas. Enter your height and weight to get your BSA in m², widely used for drug dosing and clinical measurements. Stroke Volume Calculator Stroke Volume Calculator is a health and wellness calculator that helps you calculate the volume of a three-dimensional shape or container. The formula used is: SV = Cardiac Output ÷ Heart Rate (or) SV = EDV − ESV. Enter values using the units shown next to each input field (e.g. kg, cm, years).