What is the cardiac index formula?

Cardiac index is calculated as CI = cardiac output (CO) / body surface area (BSA).

How is BSA calculated?

BSA is calculated with the Mosteller formula: √(height in cm × weight in kg / 3600).

What inputs are required?

Enter cardiac output in L/min, height in cm, and weight in kg. Decimal places are optional.

What is the normal cardiac index range?

The stated normal range is 2.5–4.0 L/min/m².

What does the calculator return?

It returns a JSON result containing BSA, cardiac index, a category, the method, and model information.

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Cardiac Index Calculator (CI)

Compute CI = CO / BSA with BSA from the Mosteller formula √(height × weight / 3600). Normal 2.5–4.0 L/min/m². Derived from Mosteller NEJM 1987, Du Bois 1916, StatPearls, LITFL. Not medical advice.

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Normal adult male: CO=5, Height=175, Weight=75 → BSA=1.91, CI=2.62 L/min/m²

BSA = √(175×75/3600) = √3.6458 = 1.909 m². CI = 5 / 1.909 = 2.62 L/min/m² — within the normal range (2.5–4.0). For a 70 kg adult this is an appropriate resting cardiac index.

{"result":"Cardiac index CI = 5 / 1.91 = 2.62 L/min/m² (Normal cardiac index).","metadata":{"input":{"co":5,"height":175,"weight":75},"result":{"bsa":1.91,"cardiacIndex":2.62,"category":"Normal cardiac index","method":"CI = CO / BSA; BSA = √(height(cm) × weight(kg) / 3600)","model":"Mosteller NEJM 1987; Du Bois 1916; StatPearls; LITFL. Not medical advice."}}}

Cardiogenic shock: CO=2.8, Height=170, Weight=70 → BSA=1.81, CI=1.55 L/min/m² (low)

BSA = √(170×70/3600) = √3.3056 = 1.818 m². CI = 2.8 / 1.818 = 1.54 L/min/m² — well below the 2.2 cutoff for low cardiac output. Consistent with cardiogenic shock, where CI < 2.2 combined with elevated PCWP (>18) and hypotension defines the Forrester subset IV (high filling pressure, low output).

{"result":"Cardiac index CI = 2.8 / 1.82 = 1.54 L/min/m² (Low cardiac index).","metadata":{"input":{"co":2.8,"height":170,"weight":70},"result":{"bsa":1.82,"cardiacIndex":1.54,"category":"Low cardiac index","method":"CI = CO / BSA; BSA = √(height(cm) × weight(kg) / 3600)","model":"Mosteller NEJM 1987; Du Bois 1916; StatPearls; LITFL. Not medical advice."}}}

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4 options

SettingsAdjust formats, ranges, numbers, and modes.4

Cardiac Output CO (L/min)numberRequiredCardiac output in L/min (from thermodilution, Fick, or echo).Height (cm)numberRequiredPatient height in centimeters, used to compute BSA via Mosteller.Weight (kg)numberRequiredPatient weight in kilograms, used to compute BSA via Mosteller.Decimal PlacesnumberOptional

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Cardiac Index Calculator (CI)

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1. Normal adult cardiac index calculation

2. Low cardiac index example

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