Calculate cardiac output from heart rate and stroke volume, with optional cardiac index via body surface area.
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Heart rate
70 bpm
Stroke volume
70 mL
Normal CO at rest: 4.0–8.0 L/min
CO = heart rate × stroke volume. BSA uses the Mosteller formula. These are reference estimates only — clinical context is essential for interpretation.
Also in Cardiovascular
Health — Cardiovascular
Cardiac output — the volume of blood the heart pumps each minute — is a fundamental measure of cardiovascular function used in clinical monitoring, exercise physiology, and critical care. This calculator derives cardiac output from heart rate and stroke volume, with optional cardiac index from body surface area.
Cardiac output (CO) equals heart rate multiplied by stroke volume. A normal resting cardiac output in adults is typically 4–8 L/min, though values outside this range may be normal depending on body size, fitness level, and physiological state.
CO (L/min) = HR (bpm) × SV (mL) ÷ 1000
Heart rate × stroke volume gives cardiac output. Divide mL by 1000 to convert to litres per minute.
Because cardiac output varies with body size, the cardiac index (CI) normalises it to body surface area: CI = CO ÷ BSA. Body surface area uses the Mosteller formula: BSA = √(height × weight ÷ 3600). A normal resting cardiac index is typically 2.5–4.0 L/min/m².
Low cardiac output may suggest heart failure, hypovolaemia, or severe bradycardia. Elevated output at rest can occur with fever, anaemia, thyrotoxicosis, or high physical fitness. During vigorous exercise, cardiac output can increase 4–5 times above resting values in trained athletes. Stroke volume is not routinely measured in clinical practice and is usually derived from echocardiography, thermodilution, or non-invasive cardiac monitoring.
Frequently asked questions
For most adults, a resting cardiac output of 4–8 L/min is considered normal. Trained endurance athletes often have higher stroke volumes and lower resting heart rates, keeping cardiac output in a similar range.
Cardiac output measures total blood pumped per minute. Cardiac index normalises this to body surface area, making it more comparable between people of different sizes. A CI of 2.5–4.0 L/min/m² is generally considered normal at rest.
Clinically, stroke volume is most commonly estimated from echocardiography or invasive monitoring. It is not typically measured directly in routine care and cannot be calculated without specialised equipment.
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