Cardiac Output & Cardiovascular Calculator
Calculate cardiac output, stroke volume, and cardiac index. Key measurements used in exercise physiology, cardiovascular health assessment, and sports science.
Cardiac Output Guide
Cardiac Output Formula
Cardiac output (CO) = Heart rate (HR) × Stroke volume (SV). Normal resting values: HR = 60-100 bpm, SV = 60-100 mL, CO = 4.0-8.0 L/min. An average resting adult pumps approximately 5 L/min — the entire blood volume circulates once per minute. Cardiac index (CI) = CO / body surface area (BSA). Normal CI = 2.5-4.0 L/min/m². CI adjusts for body size — useful for comparing across individuals. The Fick principle: CO = O₂ consumption / (arterial O₂ content − venous O₂ content) — the gold standard for
Stroke Volume and Its Determinants
Stroke volume (volume ejected per beat) is determined by three factors: preload (end-diastolic volume — the 'fill'), afterload (resistance against which the heart pumps — affected by blood pressure and peripheral resistance), and contractility (intrinsic strength of the cardiac muscle). Frank-Starling law: within limits, increased preload increases stroke volume (the more the ventricle fills, the harder it contracts). Exercise dramatically increases SV — elite athletes can reach SV of 150-200 mL
Mean Arterial Pressure
MAP = (systolic + 2 × diastolic) / 3. This approximation accounts for the fact that diastole (heart relaxation) occupies approximately two-thirds of the cardiac cycle. MAP represents the average pressure driving blood through the systemic circulation. Normal MAP = 70-100 mmHg. MAP < 60 mmHg is associated with inadequate organ perfusion (critical in trauma and septic shock). MAP is more clinically relevant than either systolic or diastolic pressure alone for assessing perfusion pressure to vital
Cardiac Output During Exercise
At rest: CO ≈ 5 L/min. Moderate exercise: CO doubles to 10-12 L/min. Maximal exercise (trained individual): CO reaches 20-25 L/min. Elite endurance athletes: CO up to 35-40 L/min during maximal exercise. Most of the increase comes from increased HR (up to 200 bpm) but SV also increases (from 70 mL at rest to 150+ mL during intense exercise). VO₂ max (maximal oxygen consumption) = CO max × maximal arteriovenous O₂ difference. Training increases CO by increasing both maximal SV (via cardiac hypert
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