How this instrument works
Ejection fraction measures how much of the blood filling the heart's left ventricle gets pumped out with each contraction, expressed as a percentage. It needs exactly two measurements: end-diastolic volume, the amount of blood in the ventricle right before it contracts, and end-systolic volume, what is left behind right after. The arithmetic is simple subtraction and division — end-diastolic volume minus end-systolic volume, divided by end-diastolic volume, times 100 — but the two volumes behind it come from an echocardiogram, MRI, or other cardiac imaging study, not from anything measured at home.
A reading of roughly 50 to 70 percent is generally considered the normal range for a healthy left ventricle, according to the American Heart Association and standard cardiology references. Below about 40 percent typically signals a heart pumping less effectively than expected, a hallmark of heart failure with reduced ejection fraction; figures in between are often described as borderline or mildly reduced, depending on the exact cutoffs a given clinician applies.
This instrument only performs the arithmetic — it has no way to judge whether an EDV or ESV entered is itself accurate, and a single ejection fraction is one measurement from one study, not a full cardiac assessment. A figure even a little above the usual range, like 80 percent from a small, vigorously contracting ventricle, can appear in a genuinely healthy heart, but very high or very low readings both deserve interpretation from a clinician who can see the full imaging study, not just the resulting percentage.
- Enter End-diastolic volume (EDV) in millilitres — the ventricle's fullest volume, just before contraction.
- Enter End-systolic volume (ESV) in millilitres — what remains right after the beat.
- Read Ejection fraction as a percentage, then compare it against the normal, reduced, and high ranges above.
- Bring the result to a clinician alongside the original imaging study, not as a stand-alone diagnosis.
Worked example — EDV 120 mL, ESV 50 mL
Subtract end-systolic from end-diastolic volume: 120 − 50 = 70 millilitres actually pumped out. Divide that by the end-diastolic volume: 70 ÷ 120 ≈ 0.5833, and multiply by 100 for an ejection fraction of about 58.33 percent — comfortably inside the roughly 50-to-70-percent range generally considered normal.
A larger, less efficient ventricle tells a different story: 150 mL down to 100 mL leaves only 50 mL pumped out, and 50 ÷ 150 × 100 gives 33.33 percent, well into the range considered reduced and a hallmark finding in heart failure with reduced ejection fraction. At the other extreme, 100 mL down to 20 mL leaves 80 mL pumped out — 80 ÷ 100 × 100 is exactly 80 percent, above the typical normal band, a figure sometimes seen in a strongly contracting, healthy heart but also one worth a clinician's own reading of the underlying study.
Questions
What counts as a normal ejection fraction?
Roughly 50 to 70 percent is generally treated as the normal range for the left ventricle, per the American Heart Association and standard cardiology references. Figures below that range suggest the ventricle is pumping less blood out per beat than expected, while figures somewhat above it are not automatically abnormal — context from the full imaging study matters more than the single percentage.
What does a low ejection fraction mean?
A reading meaningfully below the normal range, often cited around 40 percent or lower, is a hallmark of heart failure with reduced ejection fraction, meaning the ventricle is not pushing out as much of its blood as expected with each beat. It is a significant clinical finding that calls for evaluation and follow-up from a cardiologist, not something to self-manage from a single number.
Can ejection fraction be too high?
A reading noticeably above the usual 50-to-70-percent band, such as 80 percent, can occur in a healthy, vigorously contracting heart — smaller chamber volumes sometimes produce higher percentages without anything being wrong. It can also reflect certain conditions in the underlying imaging study, so an unusually high figure is generally worth discussing with the clinician who read the scan rather than treated as automatically good news.
What is the difference between EDV and ESV?
End-diastolic volume is how much blood sits in the left ventricle at its fullest, just before a contraction begins; end-systolic volume is what remains right after that contraction ends. The gap between the two, divided by the starting volume, is exactly what ejection fraction measures — how much of a full chamber actually gets pushed out with each beat.
Can I measure EDV and ESV myself at home?
No — both figures come from cardiac imaging, typically an echocardiogram, cardiac MRI, or a nuclear scan, read and reported by a trained technician or clinician. This calculator only performs the arithmetic on numbers already provided by that kind of study; it has no way to generate or verify EDV and ESV on its own.
Does one ejection fraction reading tell the whole story?
Not on its own. Ejection fraction is one measurement from one study at one point in time, and clinicians typically weigh it alongside symptoms, other imaging findings, and how the figure changes across repeat studies. A single percentage, however precisely calculated, is a starting point for a clinical picture, not the whole picture itself.
References
- American Heart Association — Ejection Fraction Measurement
- StatPearls — Ejection Fraction (NCBI Bookshelf)
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.