Ejection Fraction (EF) Calculator
Calculate left ventricular ejection fraction from end-diastolic and end-systolic volume — with stroke volume and the heart-failure category.
How it works
Ejection fraction is the proportion of blood in the ventricle at the end of diastole that is actually ejected with the next beat: EF (%) = (EDV − ESV) ÷ EDV × 100. The numerator, EDV − ESV, is the stroke volume.
A normal left ventricular ejection fraction is 50–70%. Heart failure is graded by EF: HFrEF (reduced) at 40% or below, HFmrEF (mildly reduced) at 41–49%, and HFpEF (preserved) at 50% or above. An EF at or below 35% is the usual threshold at which an implantable defibrillator is considered. Read the full explanation in our ejection fraction guide.
Frequently asked questions
How do you calculate ejection fraction?
EF (%) = (EDV − ESV) ÷ EDV × 100, where EDV is end-diastolic volume and ESV is end-systolic volume. The difference between them is the stroke volume.
What is a normal ejection fraction?
A normal left ventricular ejection fraction is 50–70%. Below 50% is abnormal, and 40% or below is classed as heart failure with reduced ejection fraction (HFrEF).
What EF is considered dangerously low?
An EF at or below 35% marks significantly impaired systolic function and is the usual threshold at which an implantable cardioverter-defibrillator is considered for primary prevention.
Is ejection fraction the same as stroke volume?
No. Stroke volume is the absolute volume ejected per beat in millilitres (EDV − ESV); ejection fraction is that volume expressed as a percentage of the end-diastolic volume.