Stroke Volume Explained: How Much Blood the Heart Pumps Per Beat

Stroke volume (SV) is the volume of blood ejected by the left ventricle per contraction. In a healthy adult at rest, SV averages 70 mL (range 50–100 mL).

SV is influenced by preload (ventricular filling), afterload (arterial resistance), and contractility. It increases with exercise (up to 100–150 mL in trained athletes) and decreases with heart failure, hemorrhage, or reduced venous return.

Visualizing 70 mL

• ≈ 2.4 US tablespoons (1 tbsp = 14.8 mL)
• ≈ A standard 1.5 oz (44 mL) shot glass filled 1.6 times
• ≈ A small medicine cup

Cardiac output (CO) = SV × Heart Rate. At rest: 70 mL × 70 bpm ≈ 4.9 L/min.