Stroke Volume Calculator

Stroke volume (SV) is the volume of blood ejected by the left ventricle with each heartbeat. It equals the end-diastolic volume (EDV, volume when the ventricle is full) minus the end-systolic volume (ESV, volume remaining after contraction): SV = EDV - ESV. Normal resting stroke volume is 60 to 100 mL per beat.

End-diastolic volume (EDV) is the volume of blood in the left ventricle at the end of filling (diastole), typically 120 to 130 mL at rest. End-systolic volume (ESV) is the volume remaining after the ventricle contracts (systole), typically 50 to 60 mL. The difference between EDV and ESV is the stroke volume.

Ejection fraction (EF) is the fraction of blood ejected per beat expressed as a percentage: EF = (SV / EDV) x 100. A normal ejection fraction is 55% to 70%. Stroke volume determines how much blood is actually pumped, while ejection fraction shows the efficiency of the ventricle as a proportion of its total capacity.

Stroke volume is increased by: higher preload (more venous return stretching the ventricle, as described by the Frank-Starling mechanism), greater contractility (stronger heart muscle contraction, as from sympathetic stimulation), and lower afterload (less resistance the heart pumps against). Regular aerobic exercise chronically increases SV by enlarging the cardiac chambers.

A low stroke volume may indicate heart failure (reduced contractility), hypovolemia (low blood volume reducing preload), severe aortic stenosis (increased afterload), or cardiac tamponade (external compression). A very low SV combined with a high heart rate may still produce an adequate cardiac output, but at the cost of increased cardiac work and myocardial oxygen demand.