Cardiac Output Calculator — CO & Cardiac Index
Cardiac output (CO) is the volume of blood your heart pumps each minute. Enter your heart rate and stroke volume to calculate CO, and add your height and weight to get the cardiac index (CI), which normalises output for body size.
bpm
mL/beat
cm
kg
Normal resting cardiac output is 4–8 L/min
- 1
HR × stroke volume
72 × 70 = 5,040 mL/minHeart rate (bpm) multiplied by stroke volume (mL/beat) gives output in mL/min. - 2
Cardiac output (mL/min → L/min)
5,040 ÷ 1000 = 5.04
How does this calculator work?
Cardiac output = Heart Rate × Stroke Volume ÷ 1000, expressed in litres per minute. Normal resting CO is 4–8 L/min. Dividing by body surface area (estimated from height and weight) gives the cardiac index (CI), with a normal range of 2.5–4.0 L/min/m².
Formula
How this is calculated
Cardiac output is the product of two factors: how many times the heart beats per minute (heart rate, HR) and how much blood is ejected with each beat (stroke volume, SV). Multiplying them — CO = HR × SV — gives the total volume per minute in millilitres; dividing by 1000 converts to litres. At rest, a healthy adult has a CO of roughly 4–8 L/min, rising to 20–25 L/min during intense exercise.
Because people differ in body size, clinicians normalise CO by dividing it by body surface area (BSA) to get the cardiac index (CI). This calculator estimates BSA using the DuBois formula (0.007184 × height_cm^0.725 × weight_kg^0.425), which gives results within a few percent of measured values for typical adults. The normal resting CI is 2.5–4.0 L/min/m².
This tool assumes a steady-state, resting measurement and uses population-average relationships. It does not replace echocardiography or thermodilution measurements used in clinical settings. Stroke volume must be measured or estimated separately — echocardiography is the standard non-invasive method.
Frequently asked questions
At rest, 4–8 L/min is the typical range for healthy adults. Cardiac output rises significantly during exercise — up to 20–25 L/min in trained athletes — and decreases in heart failure.
Stroke volume is the amount of blood ejected from the left ventricle with each heartbeat, typically 60–100 mL at rest. It depends on ventricular filling (preload), the force of contraction (contractility), and resistance to outflow (afterload).
Cardiac index (CI) divides cardiac output by body surface area, making it comparable across people of different sizes. A CI of 2.5–4.0 L/min/m² is normal; values below 2.2 suggest cardiogenic shock in the right clinical context.
Also known as
TG we-Calculate Editorial Team. (2026). Cardiac Output Calculator — CO & Cardiac Index [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/cardiac-output-calculator
TG we-Calculate Editorial Team. "Cardiac Output Calculator — CO & Cardiac Index." TG we-Calculate. 2026. https://we-calculate.com/calculator/cardiac-output-calculator.
TG we-Calculate Editorial Team, "Cardiac Output Calculator — CO & Cardiac Index," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/cardiac-output-calculator
@misc{wecalculate_cardiac_output_calculator, title = {Cardiac Output Calculator — CO & Cardiac Index}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/cardiac-output-calculator}}, year = {2026}, note = {TG we-Calculate} }
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