Cardiac Index Calculator
Calculate cardiac index — cardiac output normalised to body size. Enter cardiac output and BSA, or compute BSA first with our calculator.
Cardiac index formula
Cardiac index (CI) = cardiac output ÷ body surface area (L/min/m²). It adjusts cardiac output for patient size so values are comparable between people.
Normal cardiac index values
| Range | Interpretation |
|---|---|
| 2.5–4.0 L/min/m² | Normal |
| < 2.2 L/min/m² | Low — cardiogenic shock territory |
| > 4.0 L/min/m² | High — e.g. sepsis, hyperthyroidism |
Cardiac index vs cardiac output
Cardiac output is the total blood pumped per minute; cardiac index divides it by BSA so a small and a large person can be compared fairly. Learn more in the hemodynamics guide.
Frequently asked questions
What is a normal cardiac index?
A normal cardiac index is 2.5–4.0 L/min/m². Below 2.2 suggests cardiogenic shock; above 4.0 can occur in sepsis or hyperthyroidism.
How do you calculate cardiac index?
Divide cardiac output (L/min) by body surface area (m²): CI = CO ÷ BSA.
What is the difference between cardiac output and cardiac index?
Cardiac output is total blood pumped per minute; cardiac index is that output divided by body surface area, so it accounts for body size.
What does a low cardiac index mean?
A cardiac index under 2.2 L/min/m² indicates inadequate output for the body's size, seen in cardiogenic shock and severe heart failure.