Stroke Volume: Normal Range, Formula & What Controls It

Stroke volume is the blood ejected with a single heartbeat — and understanding its three levers is the key to understanding the whole circulation.

What is stroke volume?

Stroke volume is the amount of blood the left ventricle ejects with each beat — normally 60–100 mL. It equals the end-diastolic volume (the filled ventricle) minus the end-systolic volume (what remains after contraction).

Stroke volume formula

Two equivalent ways to express it:

• SV = end-diastolic volume − end-systolic volume
• SV = cardiac output ÷ heart rate (rearranged from CO = HR × SV)

Indexed to body size it becomes the stroke volume index. Compute it with our stroke volume calculator.

Normal stroke volume values

Measure	Normal range
Stroke volume	60–100 mL
Stroke volume index	33–47 mL/m²
Ejection fraction	50–70%

The three determinants of stroke volume

• Preload — the degree of ventricular filling before contraction. By the Frank-Starling mechanism, more stretch produces a stronger contraction and a larger stroke volume.
• Afterload — the resistance the ventricle ejects against (chiefly systemic vascular resistance). Higher afterload reduces stroke volume.
• Contractility — the intrinsic strength of contraction, increased by sympathetic stimulation and inotropic drugs.

Stroke volume variation & fluid responsiveness

In ventilated patients, stroke volume variation (SVV) — the beat-to-beat change in stroke volume across the respiratory cycle — is used to predict whether giving fluid will actually raise cardiac output. A high SVV (roughly > 13%) suggests the patient is preload-responsive. It's a modern, dynamic alternative to static pressures like CVP.

Key takeaways

• Stroke volume is the blood ejected per beat, normally 60–100 mL.
• SV = end-diastolic − end-systolic volume, or cardiac output ÷ heart rate.
• Its three levers are preload, afterload, and contractility.
• Stroke volume variation helps predict fluid responsiveness.

Frequently asked questions

What is a normal stroke volume?

About 60–100 mL per beat; the stroke volume index (per m² of body surface area) is roughly 33–47 mL/m².

What is the stroke volume formula?

Stroke volume = end-diastolic volume − end-systolic volume, or equivalently cardiac output ÷ heart rate.

What are the determinants of stroke volume?

Preload, afterload, and contractility.

How does afterload affect stroke volume?

Higher afterload — for example a raised systemic vascular resistance — reduces stroke volume, because the ventricle must work harder to eject.

What is stroke volume variation?

The beat-to-beat change in stroke volume during the respiratory cycle in ventilated patients; a high value predicts that fluid will increase cardiac output.

What is the difference between stroke volume and ejection fraction?

Stroke volume is the absolute blood ejected per beat; ejection fraction is that volume as a percentage of the filled ventricle.