π« Ejection Fraction Calculator
What share of blood the heart pumps out each beat.
For informational purposes only, not medical advice. Consult a healthcare professional.
Ejection fraction is the percentage of blood the left ventricle pumps out with each beat: (EDV minus ESV) divided by EDV. An EDV of 120 mL and ESV of 50 mL gives 58.3%, comfortably normal. Normal is 55% or higher; 40% or less is the reduced range that defines heart failure with reduced EF. Enter your echo volumes above.
How to Use This Calculator
EDV and ESV come from an echocardiogram, cardiac MRI, or nuclear scan report. They are the volumes of the left ventricle at its fullest and its emptiest.
Find the end-diastolic volume (EDV) on your report, in milliliters. Typical adult values run 90 to 150 mL.
Find the end-systolic volume (ESV), usually 30 to 70 mL. It must be smaller than the EDV; the calculator flags it otherwise.
Read the EF percent, the stroke volume (the mL actually ejected per beat), and the category. Compare against the bands below, not against a single "perfect" number.
The Formula
The ventricle fills to EDV, squeezes down to ESV, and the difference is the stroke volume ejected into the aorta. EF is that stroke volume as a share of the full ventricle. It is a ratio, not an absolute output: a small heart and a large heart can share an EF of 60% while moving very different stroke volumes, which is why cardiac output (stroke volume times heart rate) is the companion number. Measurement method matters too: echo EF by the biplane Simpson method can differ from MRI by several points, so trends should be compared within the same modality.
Worked Example
EDV 120 mL, ESV 50 mL: stroke volume 70 mL, EF = 70/120 = 58.3%, normal. Now EDV 180 mL, ESV 120 mL: stroke volume 60 mL, EF = 60/180 = 33.3%, reduced. Note the second heart ejects almost as much per beat (60 vs 70 mL) but at a far worse EF, because the ventricle is dilated and most of its volume sloshes back and forth rather than going forward. That dilated, inefficient pattern is the signature of systolic heart failure, and it shows why EF captures pump efficiency in a way stroke volume alone cannot.
EF Categories and What They Mean
| EF | Category | Clinical meaning |
|---|---|---|
| 55% or higher | Normal | Typical healthy pump function |
| 41 - 54% | Mildly reduced | Borderline; monitor, find the cause |
| 40% or less | Reduced (HFrEF) | Heart failure with reduced EF; guideline therapy indicated |
Guidelines split heart failure by EF: HFrEF at 40% or below, HFmrEF (mildly reduced) at 41 to 49%, and HFpEF (preserved) at 50% or above with heart failure symptoms. That last category surprises people: you can have heart failure with a "normal" EF when the ventricle is stiff and cannot fill, rather than weak and cannot squeeze. So EF rules out a weak pump but never rules out heart failure by itself. Symptoms, BNP levels, and diastolic measurements complete the picture. A single low reading also deserves confirmation: dehydration, a fast heart rate during the echo, or a poor acoustic window can all nudge the number. For the broader cardiac picture, our blood pressure checker and Framingham risk calculator cover the pressures and risk factors that damage the pump over decades, and our heart failure prognosis page explains how clinicians think about outlook by severity.
When EF Changes Management
Crossing below 40% changes treatment: guideline-directed therapy (ACE inhibitor or ARNI, beta-blocker, MRA, SGLT2 inhibitor) is indicated for HFrEF regardless of symptoms, because these drugs cut mortality. Below 35% with symptoms despite therapy, device therapy enters the conversation: ICDs for sudden-death prevention, cardiac resynchronization for wide QRS. EF also gates procedures: some chemotherapy regimens pause if EF falls, and valve surgery timing leans on it. Improvement matters as much as the absolute number; an EF that rises from 30% to 45% on therapy is a strong response even though 45% is still below normal. Track the trend on the same machine and method, and let the cardiologist interpret single readings in context.
Limits of the Number
EF has a dirty secret: it is load-dependent. Drop the blood pressure or the fluid volume and EF rises without the heart muscle changing at all. Severe mitral regurgitation inflates EF because blood ejects backward into the atrium and counts as "ejected." Athletes can have EFs in the low 50s with enormous stroke volumes and superb fitness. And echo EF carries a measurement error of roughly plus or minus 5%, so a change from 55% to 50% may be noise. Treat small moves as noise, large moves as signal, and always read EF alongside the clinical story.
EF After Heart Attack: Why It Gets Rechecked
After a myocardial infarction, EF is typically measured before discharge and again in 6 to 12 weeks, because stunned heart muscle can recover. An EF of 32% at discharge that rises to 46% at three months changes everything about device decisions, which is why ICD implantation for primary prevention waits at least 40 days post-MI and 90 days post-revascularization. Early low readings reflect stunning and swelling as much as dead muscle; the repeat echo shows what is permanent. Cardiac rehab during that window improves the odds of recovery.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is a normal ejection fraction?
55% to 70% by echocardiography. Values in this range mean the left ventricle ejects a normal share of its volume each beat. Athletic hearts and measurement variation mean the low 50s can still be normal in context.
What ejection fraction is considered heart failure?
40% or below defines heart failure with reduced ejection fraction (HFrEF). But heart failure can exist with normal EF too (HFpEF), when the ventricle is stiff rather than weak. EF alone never rules heart failure in or out.
Can ejection fraction improve?
Yes. Guideline-directed medications, treating the cause (like blocked arteries or alcohol), cardiac rehab, and devices can raise EF substantially. An EF climbing from 30% to 45% on therapy is a strong, meaningful response.
What is the difference between EF and stroke volume?
Stroke volume is the absolute mL ejected per beat; EF is that volume as a percentage of the full ventricle. A dilated failing heart can have a near-normal stroke volume with a terrible EF, which is why the ratio matters.
Is 45% ejection fraction bad?
It is below normal and falls in the mildly reduced (41-49%) range. It warrants a cardiology workup to find the cause and usually monitoring or treatment, but it is not the severe range. Context and trend matter more than the single number.
How is ejection fraction measured?
Most often by echocardiogram using the biplane Simpson method, which traces the ventricle in two views. Cardiac MRI is more precise; nuclear scans and CT can also measure it. Compare trends within the same method.
Can dehydration lower ejection fraction?
It can nudge the number because EF is load-dependent: less filling volume changes the ratio. A fast heart rate during the test has a similar effect. Repeat measurements under stable conditions before concluding anything changed.
What EF qualifies for a defibrillator (ICD)?
Generally 35% or below with symptomatic heart failure despite at least 3 months of optimal medical therapy, for primary prevention of sudden cardiac death. The exact criteria depend on the cause and QRS width; a cardiologist decides.
Does a normal EF mean my heart is healthy?
Not necessarily. Valve disease, diastolic dysfunction (HFpEF), coronary blockages, and arrhythmias can all exist with a normal EF. EF measures squeeze, not the whole heart. Symptoms always deserve evaluation regardless of the number.
How accurate is echo ejection fraction?
Within about plus or minus 5% in good hands, worse with poor image quality. That means small changes between studies may be noise. Cardiac MRI is the reference standard when precision matters.