Hemodynamics Calculators

The hemodynamics calculators compute the three core measures that describe how effectively the heart delivers blood: cardiac output (CO), cardiac index (CI), and stroke volume (SV). Each calculator solves for any variable in the equation, shows the substituted arithmetic step by step, and links to the underlying physiology.

Use these together to interpret bedside data: cardiac output tells you total flow per minute, cardiac index normalizes that flow to body size for comparison across patients, and stroke volume isolates the per-beat ejection that drives ventricular performance.

When to use these calculators

Cardiac output, cardiac index, and stroke volume are the foundation of hemodynamic monitoring in the ICU, cath lab, and operating room. They come up in fluid resuscitation, shock classification, vasoactive titration, and pre-/post-operative cardiac assessment.

Use cardiac output to track total minute flow during resuscitation or weaning. Use cardiac index when comparing patients of different body sizes or evaluating whether a measured CO is adequate for a given person. Use stroke volume to assess ventricular performance independently of heart rate — particularly when chronotropic support or tachycardia is masking the contractility picture.

Each calculator can also be inverted: solve for heart rate to find the pacing target that achieves a desired CO, or solve for stroke volume when CO and HR are known from monitoring.

Frequently Asked Questions

What's the difference between cardiac output and cardiac index?

Cardiac output is total minute flow in L/min. Cardiac index divides that flow by body surface area (BSA), giving a size-normalized value in L/min/m². A 4 L/min cardiac output may be adequate for a small adult and inadequate for a large one — the index makes that explicit. Normal cardiac index is roughly 2.5 to 4.0 L/min/m². [REVIEW: confirm normal CI range against your reference].

What is a normal cardiac output at rest?

Most healthy adults at rest have a cardiac output between 4 and 8 L/min. Athletes, pregnant patients, and septic patients can fall outside that range — context matters when interpreting a single number. [REVIEW: confirm 4-8 L/min range against your reference].

When is stroke volume more useful than cardiac output?

Stroke volume isolates per-beat ejection from heart rate, which helps when tachycardia is propping up cardiac output despite poor ventricular performance. It also guides titration of preload, afterload, and contractility interventions whose effect appears in the SV column before CO catches up.

Can cardiac output be normal even when tissue perfusion is poor?

Yes. A normal global cardiac output does not guarantee adequate microcirculatory flow or oxygen delivery to every tissue bed. Sepsis, severe vasoconstriction, and regional ischemia can produce poor perfusion despite an acceptable output.

How are these values measured clinically?

Thermodilution via a pulmonary artery catheter remains the reference standard for cardiac output. Less invasive options include echocardiography (Doppler-based), arterial pulse-contour analysis, and bioimpedance or bioreactance techniques. Each has trade-offs in accuracy, invasiveness, and continuous-monitoring capability.