Ejection Fraction Calculator: How It Works

This calculator estimates your ejection fraction (EF) — the percentage of blood your left ventricle pumps out with each heartbeat — based on the volumes you enter from an echocardiogram or cardiac MRI. You input the end-diastolic volume (EDV, the amount of blood in the ventricle just before it contracts) and the end-systolic volume (ESV, the amount left after contraction), and the calculator returns your EF as a percentage, along with stroke volume. It is a quick way to check where you fall on the normal range (55–70%) and to track changes over time.

Formula

The ejection fraction is calculated using the formula:

EF (%) = (EDV − ESV) / EDV × 100

• EDV = end-diastolic volume (mL) — the volume of blood in the left ventricle at the end of filling (diastole).
• ESV = end-systolic volume (mL) — the volume of blood remaining in the left ventricle after contraction (systole).
• EF = ejection fraction (%), the proportion of EDV that is pumped out.

The difference (EDV − ESV) is the stroke volume (SV), the amount of blood ejected per beat. EF is simply stroke volume divided by EDV, expressed as a percentage.

Worked Example

Using the default values from the calculator: EDV = 120 mL and ESV = 50 mL.

1. Stroke volume = EDV − ESV = 120 − 50 = 70 mL.
2. EF = (70 / 120) × 100 = 58.33%.
3. Rounded to one decimal place, the calculator shows 58.3%.

This is a normal ejection fraction, within the typical range of 55–70%.

When to Use This Calculator

You would use this calculator after you have had an imaging test that reports your EDV and ESV. These numbers come from an echocardiogram (ultrasound of the heart), a cardiac MRI, or a nuclear medicine scan (MUGA). The calculator is useful for:

• Understanding your EF when your report gives raw volumes but not the percentage.
• Tracking changes between tests — a drop of 5–10 percentage points can be significant.
• Seeing how stroke volume and EF relate to each other.

It is not a substitute for a doctor’s interpretation. EF is one of many measures of heart function, and a single number does not tell the whole story.

How to Read the Result

Ejection fraction is reported as a percentage. The normal range is generally considered 55–70%. Here is how doctors typically classify EF:

• Normal: 55–70%
• Mildly reduced (borderline): 50–54%
• Reduced (heart failure with reduced EF): below 40–50% (guidelines vary; many use 40% as the cutoff for heart failure with reduced EF)
• Very low: below 30% — associated with severe systolic dysfunction

An EF above 70% can occur in some conditions, such as hypertrophic cardiomyopathy, and may also be a concern. Always interpret your EF in the context of your symptoms and other tests.

Common Mistakes and Misconceptions

A frequent mistake is entering the wrong volumes — for example, using the right ventricular volumes instead of left ventricular volumes. Another is confusing EDV and ESV: if you swap them, the calculator will give a negative EF (which is impossible). Also, be careful with units: volumes are in milliliters (mL), not liters. If your report lists volumes in liters, multiply by 1000 first.

A common misconception is that EF is the same as cardiac output. It is not. Cardiac output = stroke volume × heart rate. A person with a low EF can sometimes have normal cardiac output if the heart rate is high. EF is a measure of pump efficiency, not total flow.

Limitations of the Formula

The EF formula is simple, but its accuracy depends entirely on the quality of the imaging measurements. Echocardiographic EF estimates can vary by ±5% between operators and even between consecutive readings. The formula assumes the ventricle is a simple shape, but real ventricles are irregular, especially after a heart attack. Advanced methods like 3D echocardiography or MRI give more precise volumes, but the same formula applies. Also, EF does not measure diastolic function (how well the ventricle fills) — a person can have heart failure with a normal EF (HFpEF).

Frequently Asked Questions

What is a normal ejection fraction?

A normal ejection fraction is generally between 55% and 70%. This means the left ventricle pumps out more than half of its blood with each beat. Values below 50% indicate reduced pumping function, and below 40% is often considered heart failure with reduced ejection fraction.

Can ejection fraction improve?

Yes, EF can improve with treatment. Medications such as beta-blockers, ACE inhibitors, and SGLT2 inhibitors, along with lifestyle changes and sometimes procedures, can help the heart remodel and pump more effectively. Some people see their EF return to normal over time.

What does a low ejection fraction mean?

A low EF (below 40–50%) means the heart is not pumping blood efficiently. This can cause symptoms like shortness of breath, fatigue, and fluid retention. It is a hallmark of heart failure with reduced ejection fraction, but it does not mean the heart is about to stop — many people live well with a low EF under medical care.

Is ejection fraction the same as heart function?

No. EF measures only the left ventricle’s pumping ability. It does not assess the right ventricle, the heart’s valves, the heart rhythm, or diastolic function. A person can have heart failure symptoms with a normal EF. Doctors use EF along with other tests like EKG, blood tests, and stress tests to get a full picture.

How is ejection fraction measured?

Ejection fraction is measured by imaging tests. The most common is an echocardiogram, which uses ultrasound. A cardiac MRI gives the most precise measurements. A MUGA scan uses a small amount of radioactive tracer. All of these methods calculate EDV and ESV, then apply the same formula.

What is the difference between stroke volume and ejection fraction?

Stroke volume is the amount of blood ejected per beat in milliliters (e.g., 70 mL). Ejection fraction is stroke volume divided by end-diastolic volume, expressed as a percentage. Stroke volume depends on body size and heart rate, while EF is a relative measure of efficiency. A small heart can have a low stroke volume but a normal EF.

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in edv | End-diastolic volume (EDV) | mL | 120 | 0
in esv | End-systolic volume (ESV) | mL | 50 | 0
out ef | Ejection fraction | % | (edv - esv) / edv * 100 | 1
out sv | Stroke volume | mL | edv - esv | 0