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Printed on 7/20/2026
For informational purposes only. This is not medical advice.
Ejection fraction (EF) is the percentage of blood the left ventricle ejects with each contraction, and it's the single most-used metric for classifying heart failure type and guiding therapy selection. This calculator uses the volumetric formula (EDV − ESV) ÷ EDV, matching what echocardiography, cardiac MRI, and nuclear imaging report. Combine with the ACC/AHA Heart Failure Staging to place a patient's overall HF trajectory, and with Cardiac Output to distinguish a pure pump-function problem from a volume/rate problem. Assess cardiovascular risk more broadly with ASCVD Risk and NYHA Functional Class for symptom staging.
Formula: EF (%) = (EDV − ESV) ÷ EDV × 100
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Ejection fraction requires two volume measurements of the left ventricle: end-diastolic volume (EDV), the LV volume at maximum filling just before contraction, and end-systolic volume (ESV), the LV volume remaining just after contraction. These are most commonly obtained from echocardiography using the biplane Simpson's method (tracing the endocardial border in two apical views), though cardiac MRI is considered the gold-standard reference method due to its superior accuracy and reproducibility, and nuclear imaging (MUGA scan, gated SPECT) and left ventriculography during cardiac catheterization are also used in specific clinical scenarios. The stroke volume (the amount of blood ejected per beat) is simply EDV minus ESV — this is the same stroke volume value used in cardiac output calculations, connecting ejection fraction to overall hemodynamic assessment.
Ejection Fraction (%) = (EDV − ESV) ÷ EDV × 100. For example, an EDV of 120 mL and ESV of 50 mL gives a stroke volume of 70 mL and an ejection fraction of 58.3% — within the normal range. This formula expresses ejection fraction as the fraction of the ventricle's total diastolic volume that gets ejected with each beat, which is why it's a percentage rather than an absolute volume — a dilated ventricle with a large stroke volume can still have a reduced ejection fraction if its end-diastolic volume is proportionally even larger.
The 2022 ACC/AHA/HFSA Heart Failure Guideline defines four EF-based categories that directly drive treatment decisions: HFrEF (heart failure with reduced ejection fraction, EF ≤40%) — the category with the strongest evidence base for GDMT (ACE-I/ARB/ARNI, beta-blocker, MRA, SGLT2 inhibitor — the 'four pillars'); HFmrEF (mildly reduced, EF 41-49%) — increasingly treated with similar GDMT to HFrEF based on more recent trial evidence; HFpEF (preserved, EF ≥50%) — where SGLT2 inhibitors are now the primary evidence-based therapy, with management otherwise focused on comorbidities (hypertension, obesity, atrial fibrillation); and HFimpEF (improved, previously reduced EF that has recovered to >40% with a ≥10-point increase) — a category recognizing that these patients still need to continue GDMT despite the improved number, since stopping therapy commonly causes relapse. A normal EF (≥55%) in a patient without heart failure symptoms doesn't require any specific heart-failure-directed therapy, though the underlying cause of any structural changes (hypertension, valve disease) should still be addressed.
Cardiologists and hospitalists diagnosing HF
Calculate or confirm EF from the echo report to correctly classify a newly diagnosed heart failure patient into HFrEF, HFmrEF, or HFpEF — the single most important branch point for selecting guideline-directed medical therapy.
Cardiologists and primary care managing chronic HF
EF classification directly determines which of the four GDMT pillars have strong trial evidence for a given patient, and tracking EF over serial echocardiograms shows whether therapy is achieving reverse remodeling.
Electrophysiologists evaluating device candidacy
EF ≤35% despite optimized GDMT for at least 3 months is a key threshold for primary prevention implantable cardioverter-defibrillator (ICD) eligibility, and EF ≤35% with wide QRS is central to cardiac resynchronization therapy (CRT) candidacy.
Anesthesiologists and surgeons evaluating surgical candidates
A reduced EF is an independent risk factor for perioperative cardiac complications and informs decisions about preoperative optimization, monitoring intensity, and anesthetic approach for major surgery.
Cardio-oncology teams monitoring chemotherapy patients
Serial EF monitoring during and after cardiotoxic chemotherapy (anthracyclines, trastuzumab) detects early cardiotoxicity — a drop of ≥10 percentage points to a value below 53% is a common threshold triggering cardioprotective intervention or chemotherapy modification.
A reduced EF can result from ischemic cardiomyopathy, non-ischemic dilated cardiomyopathy, valvular disease, tachycardia-induced cardiomyopathy, or peripartum cardiomyopathy, among others — the number alone doesn't tell you the etiology, which is essential for both prognosis and treatment beyond standard GDMT.
Subgroup analyses of major HF trials (and more targeted contemporary trials) show that patients in the 41-49% range generally benefit from the same four-pillar GDMT approach as HFrEF, which is why the 2022 guidelines grouped their treatment recommendations more closely than earlier classifications did.
The TRED-HF trial and subsequent evidence show that patients whose EF recovers with treatment (HFimpEF) commonly relapse if GDMT is withdrawn — improved EF reflects successful treatment, not cure, and therapy should generally continue indefinitely absent a strong reason to stop.
Cardiac MRI is generally considered more accurate and reproducible than 2D echo (which relies on geometric assumptions), and can report an EF several percentage points different from a same-day echo. When EF is borderline near a treatment-changing threshold (e.g., 34% vs 36% for ICD eligibility), consider confirming with a second modality.
Poor acoustic windows (obesity, COPD), irregular rhythms (atrial fibrillation causing beat-to-beat volume variability), and foreshortened apical views all reduce measurement reliability on 2D echo — 3D echo or cardiac MRI can be considered when accuracy is critical and initial imaging quality is suboptimal.
A substantial proportion of heart failure patients, particularly older adults, women, and those with hypertension, diabetes, or obesity, have heart failure with preserved ejection fraction — normal EF does not exclude heart failure when symptoms and other objective evidence (elevated natriuretic peptides, diastolic dysfunction, structural changes) are present.
EF ≥55% is normal, 50-54% is borderline, 41-49% is HFmrEF, and ≤40% is HFrEF per 2022 ACC/AHA/HFSA criteria. Classification directly determines which guideline-directed medical therapies have the strongest evidence base for a given patient.
Use whenever LV end-diastolic and end-systolic volumes are available from echocardiography, cardiac MRI, or nuclear imaging, to calculate or confirm ejection fraction and classify heart failure type for treatment planning.
Accuracy depends on imaging quality and modality — 2D echo relies on geometric assumptions and can be affected by poor acoustic windows or irregular rhythms. A normal EF does not exclude heart failure (HFpEF), and EF alone does not indicate the underlying etiology of cardiomyopathy.
Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.
April 21, 2026 · trust-baseline
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