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About this tool
Calculate cardiac output and cardiac index from heart rate and stroke volume with clinical reference ranges.
The Cardiac Output Calculator computes cardiac output as CO = heart rate x stroke volume / 1000, giving litres per minute from a bpm value and a stroke volume in millilitres. Add height and weight and it also returns body surface area by the Mosteller formula, BSA = the square root of (height in cm x weight in kg / 3600), and divides CO by BSA to give cardiac index in L/min/m2. Results are placed against reference bands and can be copied or downloaded as a plain-text report. It is an educational aid for students and clinicians, not a substitute for clinical judgement.
Open Cardiac Output Calculator on AltFTool — it loads instantly in your browser.
Enter Heart Rate (bpm) and Stroke Volume (mL); switch Calculation Method to 'CO + CI (with BSA)' to add Height (cm) and Weight (kg).
Press 'Calculate CO' — the gauge shows CO = HR × SV / 1000 in L/min, with minute volume in mL/min and, in CI mode, cardiac index from Mosteller BSA.
Compare the figure against Cardiac Output Ranges (4.0 – 8.0 L/min normal) and Cardiac Index Ranges (2.5 – 4.0 L/min/m² normal), then use 'Copy Report' or Download to save a CO_Report_<value>Lmin.txt file.
Mosteller BSA is calculated from height and weight and applied automatically, so a 5 L/min output is judged against the patient's size.
Both CO and CI are classified low, normal or high with a short note on what each band commonly reflects.
The report lists the inputs, CO, minute blood volume in mL/min, CI and the formulas used, so the arithmetic can be checked by someone else.
Cardiac output equals heart rate multiplied by stroke volume: CO = HR x SV. With HR in beats per minute and SV in millilitres, the product is divided by 1,000 to express the answer in litres per minute — 70 bpm x 70 mL gives 4.9 L/min.
This tool uses 4.0 to 8.0 L/min as the adult normal band, flagging below 4.0 as low and above 8.0 as high. High readings are not automatically abnormal — exercise, fever, anaemia and sepsis all raise output — so the figure needs clinical context.
Cardiac index is cardiac output divided by body surface area, reported in L/min/m2, so it corrects for how big the patient is. The tool treats 2.5 to 4.0 L/min/m2 as normal and values under 2.2 as low, a range associated with cardiogenic shock and severe heart failure.
Mosteller: BSA in m2 is the square root of (height in cm x weight in kg divided by 3600). It is the most widely used bedside formula; other formulas such as Du Bois can give slightly different values, so state which one you used when recording a result. This calculator is informational and clinical decisions should rest with a qualified clinician.
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