Cardiac Index Calculator

Cardiac Index Calculator for Cardiology. Read the output and index together. Neither a low number nor a reference-range number independently establishes the presence or absence of shock. The component deliberately does not assign a diagnosis.

For shared guidance on choosing a tool and documenting results, read the clinical calculator workflow.

How this calculator works

Cardiac index = cardiac output / body surface area. This is arithmetic indexing of an existing measurement, not a new measurement of flow. The NCI definition is available at https://ncbi.nlm.nih.gov/medgen/606706.

When to use this calculator

Check a hemodynamic report or compare output with a recorded body size. First confirm that the monitor has not already reported an indexed value. Preserve the method and time of the original output measurement.

Inputs used

  • Measured cardiac output in L/min
  • Body surface area in m² from the same assessment

Clinical interpretation

Read the output and index together. Neither a low number nor a reference-range number independently establishes the presence or absence of shock. The component deliberately does not assign a diagnosis.

Worked example

Output 5.4 L/min and BSA 1.8 m² give 5.4 / 1.8 = 3.00 L/min/m². With the same output and BSA 2.4 m², the index is 2.25. The lower index here comes entirely from the denominator, not a fall in measured flow.

Limitations and safety notes

BSA indexing can be misleading at body-size extremes. Measurement error in cardiac output is carried into the result. A mathematical zero is not a reassuring finding. This page does not select fluids, inotropes or invasive monitoring.

Frequently asked questions

Should I enter 5400 for output reported as 5400 mL/min?

No. Convert to 5.4 L/min first. A unit error makes the index 1000-fold too large.

References

  • NCI definition via NLM MedGen. https://ncbi.nlm.nih.gov/medgen/606706
  • Hoffman, 2018. Pediatric indexing limitations, original analysis. https://pubmed.ncbi.nlm.nih.gov/29387918/

Editorial review and citation methodology

Maintained by the Quick Medical Calculator Editorial Team. Content record date: September 9, 2026. A content date is not evidence of independent clinical review. Individual clinical sign-off is not recorded on this page.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

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