Goal
Estimate cardiac index from cardiac output and body surface area, or derive cardiac output from heart rate and stroke volume before indexing it.
Cardiac Index Calculator
Estimate cardiac index from cardiac output and body surface area, or derive cardiac output from heart rate and stroke volume before indexing it.
Key facts
- What it does
- Estimate cardiac index from cardiac output and body surface area, or derive cardiac output from heart rate and stroke volume before indexing it.
- Formula
Cardiac index = cardiac output ÷ body surface area. When cardiac output is derived, cardiac output (L/min) = heart rate (beats/min) × stroke volume (mL/beat) ÷ 1000.- You enter
- How should cardiac output be supplied? · Cardiac output · Heart rate · Stroke volume · Body surface area
- Worked example
- Cardiac index = 5 ÷ 1.9 = 2.6316 L/min/m².
A clearer path to an answer
From your question to a useful result
This page keeps the calculation transparent: define the goal, enter the matching values, inspect the method, and decide what the result means in your situation.
Inputs
How should cardiac output be supplied? · Cardiac output · Heart rate · Stroke volume · Body surface area
Method
Cardiac index = cardiac output ÷ body surface area. When cardiac output is derived, cardiac output (L/min) = heart rate (beats/min) × stroke volume (mL/beat) ÷ 1000.
Next step
Calculate, review the assumptions below, then compare a related tool when the decision needs more context.
Cardiac Index Calculator
Estimate cardiac index from cardiac output and body surface area, or derive cardiac output from heart rate and stroke volume before indexing it.
Open the Cardiac Index Calculator pageMore health tools
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Result
Enter your values above and choose Calculate to see the result here.
Calculation map
Follow the path from input to answer
01
Inputs (5)
- How should cardiac output be supplied? Ready
- Cardiac output Ready
- Heart rate Ready
- Stroke volume Ready
- +1 more input
02
Formula
Cardiac index = cardiac output ÷ body surface area. When cardiac output is derived, cardiac output (L/min) = heart rate (beats/min) × stroke volume (mL/beat) ÷ 1000.
Bounded, transparent calculation
03
Result
- Calculate to preview the result.
Recent runs
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Formula, assumptions, and example
Formula: Cardiac index = cardiac output ÷ body surface area. When cardiac output is derived, cardiac output (L/min) = heart rate (beats/min) × stroke volume (mL/beat) ÷ 1000.
Cardiac index expresses cardiac output relative to body surface area so a flow value can be compared with the person’s size. The page keeps the direct-output and heart-rate/stroke-volume paths visible and shows the units at each step.
- Cardiac output is entered in L/min or derived from beats per minute and millilitres per beat.
- Body surface area is supplied by the user from an accepted measurement or BSA method.
- The unit conversion divides millilitres per minute by 1000 to obtain litres per minute.
- A measurement method such as echocardiography or catheterization has its own uncertainty and is not validated by this page.
- The output is an index for arithmetic comparison, not a diagnosis or a perfusion assessment.
- The calculator does not choose a clinical threshold, normalize to another body-size convention, or infer a patient’s condition.
- Symptoms, blood pressure, rhythm, oxygenation, lactate, examination, and the original report remain essential to interpretation.
- Urgent symptoms or suspected shock require immediate local medical evaluation rather than an online result.
Worked example: Cardiac index = 5 ÷ 1.9 = 2.6316 L/min/m².
Displayed input contract
- How should cardiac output be supplied? · 2 choices
- Cardiac output · minimum 0.01 · maximum 50
- Heart rate · minimum 20 · maximum 300
- Stroke volume · minimum 1 · maximum 500
- Body surface area · minimum 0.2 · maximum 5
The displayed limits are checked before the handler runs. Model-specific domain checks may also reject impossible or non-finite inputs.
Methodology: This calculator follows the WorldCalculate input, formula, precision, and boundary policy. Read the official methodology.
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Answer-first guide
How to use the Cardiac Index Calculator for a real question
Estimate cardiac index from cardiac output and body surface area, or derive cardiac output from heart rate and stroke volume before indexing it. Start with one clearly defined goal, enter values in the units shown, and keep the result attached to the assumptions below.
What this answers
This tool is useful when your question includes cardiac index calculator, cardiac output indexed to body surface area, cardiac index formula. It returns the outputs declared in the calculator contract rather than a live quote, approval, diagnosis, or professional sign-off.
What you enter
How should cardiac output be supplied? · Cardiac output · Heart rate · Stroke volume · Body surface area. Keep the same time period, unit system, and currency wherever the form requires comparable values.
How to check it
Run the worked example first, compare its output with the page's example, then change one input at a time. This makes an unexpected result easier to trace to a unit, boundary, or assumption.
Three checks before you rely on the answer
- Match the question. Confirm that the result means the quantity you need, not a similar-sounding percentage, balance, rate, or estimate.
- Match the inputs. Use the requested units and period, and read each hint before replacing the example values with your own.
- Read the boundary. Review the assumptions and limits. Cardiac output is entered in L/min or derived from beats per minute and millilitres per beat.
Need a wider view? Browse Health Calculators or compare the related tools below. The WorldCalculate methodology explains how formulas, examples, limits, and revisions are reviewed.
How to use the Cardiac Index Calculator
- Enter How should cardiac output be supplied?
- Enter Cardiac output (L/min).
- Enter Heart rate (beats/min).
- Enter Stroke volume (mL/beat).
- Enter Body surface area (m²).
- Choose Calculate and read the result panel.
- Use Download PDF or Download Word to save a result sheet.
Formula
Cardiac index = cardiac output ÷ body surface area. When cardiac output is derived, cardiac output (L/min) = heart rate (beats/min) × stroke volume (mL/beat) ÷ 1000.
Cardiac index expresses cardiac output relative to body surface area so a flow value can be compared with the person’s size. The page keeps the direct-output and heart-rate/stroke-volume paths visible and shows the units at each step.
Worked example
Cardiac index = 5 ÷ 1.9 = 2.6316 L/min/m².
Assumptions and limits
- Cardiac output is entered in L/min or derived from beats per minute and millilitres per beat.
- Body surface area is supplied by the user from an accepted measurement or BSA method.
- The unit conversion divides millilitres per minute by 1000 to obtain litres per minute.
- A measurement method such as echocardiography or catheterization has its own uncertainty and is not validated by this page.
- The output is an index for arithmetic comparison, not a diagnosis or a perfusion assessment.
- The calculator does not choose a clinical threshold, normalize to another body-size convention, or infer a patient’s condition.
- Symptoms, blood pressure, rhythm, oxygenation, lactate, examination, and the original report remain essential to interpretation.
- Urgent symptoms or suspected shock require immediate local medical evaluation rather than an online result.
Who uses this calculator?
- Students learning how cardiac output is indexed
- Clinicians or trainees checking transparent unit arithmetic
- Readers comparing a reported cardiac output with body surface area
When is it useful?
- Convert a reported cardiac output into L/min/m².
- Check the heart-rate times stroke-volume pathway before indexing output.
- Show the difference between flow and body-size-indexed flow in a teaching note.
Context and background
How health estimates should be read
Health calculators use measurements and population-level relationships to produce screening or planning estimates. They describe the supplied model; they do not diagnose, prescribe, or replace clinical judgment.
Many familiar health formulas began as practical ways to summarize measurements. Their limits matter as much as their output because individual bodies, medications, conditions, and professional standards vary.
Research and review
How this guide was researched
Researched by Hassan ALRowaie, Founder and editorial researcher at WorldCalculate.
This guide follows the live calculator's declared inputs, formula, worked example, assumptions, validation boundaries, and source-backed methodology. The review date describes editorial review of the calculator explanation; it is not a promise that external facts or rates remain current.
Cardiac index is a compact way to express cardiac output in relation to body surface area. WorldCalculate makes the unit conversion visible so a learner can follow how a reported flow becomes an indexed value without mistaking the arithmetic for a complete hemodynamic assessment.
What cardiac index means
Cardiac output describes the volume of blood pumped per minute. Cardiac index divides that flow by body surface area, giving a size-indexed value in litres per minute per square metre.
Indexing can make comparisons more meaningful, but it does not remove uncertainty from the original measurement or replace the patient’s clinical picture.
Cardiac index formula
The core relationship is cardiac index = cardiac output ÷ body surface area. If the page first derives output, heart rate in beats per minute is multiplied by stroke volume in millilitres per beat and divided by 1000.
Keeping litres, millilitres, minutes, and square metres explicit prevents a common factor-of-1000 error.
How to use the calculator
Choose direct cardiac output when a report already gives output in L/min. Choose the second path when you are checking a heart-rate and stroke-volume calculation.
Enter the body surface area in square metres and read both the output and the indexed result. The intermediate values are displayed for auditing.
Worked example
With an output of 5 L/min and a body surface area of 1.9 m², the index is 5 ÷ 1.9, or about 2.63 L/min/m².
That number describes the entered data; it does not identify why the flow is high or low.
Where the numbers come from
Cardiac output can be measured or estimated by several methods, including imaging and invasive hemodynamic techniques. Stroke volume may itself be derived from ventricular volumes or another measurement model.
Do not mix values from different time points or methods without understanding the original report.
Reading the result responsibly
A cardiac index should be considered alongside perfusion, blood pressure, rhythm, oxygenation, filling pressures where available, symptoms, and the reason the measurement was obtained.
A single number is not a universal diagnosis threshold. Protocols and clinical settings can use different reference frameworks.
Common input mistakes
Entering a stroke volume in litres instead of millilitres makes the derived output one thousand times too small. Entering BSA in square centimetres creates a similar unit problem.
If the direct-output mode is selected, the direct output field is the source value; if the stroke-volume mode is selected, the page derives output from the two component inputs.
Safety and limitations
This page is an educational arithmetic tool. It cannot detect shock, heart failure, valve disease, arrhythmia, or measurement error.
Seek urgent local care for severe breathlessness, chest pain, fainting, confusion, cold or mottled skin, or other emergency symptoms rather than waiting for a calculator result.
FAQs
Is cardiac index the same as cardiac output? No: index is output divided by body surface area. Does it diagnose heart failure? No. Can a normal-looking value rule out illness? No; interpretation depends on the measurement and the person.
Frequently asked questions
What is the Cardiac Index Calculator?
Estimate cardiac index from cardiac output and body surface area, or derive cardiac output from heart rate and stroke volume before indexing it.
What is the formula for the Cardiac Index Calculator?
Cardiac index = cardiac output ÷ body surface area. When cardiac output is derived, cardiac output (L/min) = heart rate (beats/min) × stroke volume (mL/beat) ÷ 1000. Cardiac index expresses cardiac output relative to body surface area so a flow value can be compared with the person’s size. The page keeps the direct-output and heart-rate/stroke-volume paths visible and shows the units at each step.
What do I need to use this calculator?
Enter How should cardiac output be supplied?, Cardiac output, Heart rate, Stroke volume, Body surface area, then choose Calculate.
What are the limits of this calculator?
Cardiac output is entered in L/min or derived from beats per minute and millilitres per beat. Body surface area is supplied by the user from an accepted measurement or BSA method. The unit conversion divides millilitres per minute by 1000 to obtain litres per minute. A measurement method such as echocardiography or catheterization has its own uncertainty and is not validated by this page. The output is an index for arithmetic comparison, not a diagnosis or a perfusion assessment. The calculator does not choose a clinical threshold, normalize to another body-size convention, or infer a patient’s condition. Symptoms, blood pressure, rhythm, oxygenation, lactate, examination, and the original report remain essential to interpretation. Urgent symptoms or suspected shock require immediate local medical evaluation rather than an online result.
Methodology
This calculator is part of the WorldCalculate library. Its formula, example, assumptions, input bounds, and output formatting follow the official methodology.
Use this calculator as part of a bigger plan
These WorldCalculate collections connect this tool with related questions while keeping each calculation separate and transparent.