Biplane EF Calculator: Ejection Fraction by Echo

This calculator estimates left ventricular ejection fraction (LVEF) using the biplane method of disks (modified Simpson’s rule) from apical four-chamber and two-chamber end-diastolic and end-systolic volumes. You enter four volumes (in mL) and get the ejection fraction as a percentage, plus stroke volume and cardiac output if you add heart rate.

Formula

The biplane ejection fraction is calculated as:

EF (%) = (EDV − ESV) / EDV × 100

where the volumes are the average of the two apical views:

• EDV = (EDV_4ch + EDV_2ch) / 2 (mL) — end-diastolic volume
• ESV = (ESV_4ch + ESV_2ch) / 2 (mL) — end-systolic volume

Stroke volume (mL) = EDV − ESV. Cardiac output (L/min) = (Stroke volume × Heart rate) / 1000.

Worked Example

Using the default values from the calculator:

1. EDV_4ch = 112 mL, ESV_4ch = 45 mL
2. EDV_2ch = 108 mL, ESV_2ch = 42 mL
3. Average EDV = (112 + 108) / 2 = 110 mL
4. Average ESV = (45 + 42) / 2 = 43.5 mL
5. EF = (110 − 43.5) / 110 × 100 = 60.5%
6. Stroke volume = 110 − 43.5 = 66.5 mL
7. Cardiac output = (66.5 × 70) / 1000 = 4.66 L/min

The calculator shows EF as 60.5%, stroke volume 66.5 mL, and cardiac output 4.66 L/min.

What Is the Biplane Method?

The biplane method of disks (also called modified Simpson’s rule) is the echocardiographic standard for measuring left ventricular volumes and ejection fraction. It works by dividing the left ventricle into a stack of elliptical disks of equal thickness. The volume of each disk is calculated from the diameters measured in two orthogonal planes: the apical four-chamber view and the apical two-chamber view. Summing the disk volumes gives the total chamber volume. This is done twice — once at end-diastole (the largest volume, just before contraction) and once at end-systole (the smallest volume, at peak contraction).

Why two planes? A single plane assumes the ventricle is a perfect ellipse, which is rarely true in disease. The biplane approach captures asymmetry, making it more accurate than monoplane (single-view) estimation. It is the method recommended by the American Society of Echocardiography and the European Association of Cardiovascular Imaging for routine LVEF assessment.

How the Calculator Works

You enter four volumes that you (or your sonographer) have already obtained from the echo machine’s software. The calculator simply averages the two end-diastolic volumes and the two end-systolic volumes, then applies the EF formula. It also gives stroke volume (the amount of blood pumped per beat) and cardiac output (the amount pumped per minute) if you provide heart rate.

The calculator assumes both views were acquired correctly and that the volumes are in milliliters. Most echo software reports volumes in mL, but double-check the unit — some older machines may report in cubic centimeters, which are numerically identical (1 mL = 1 cm³), so no conversion is needed. If your volumes are in liters, multiply by 1000 before entering.

How to Read the Result

Ejection fraction is a percentage of the end-diastolic volume that is ejected with each beat. A normal LVEF is typically 52–72% in men and 54–74% in women, though exact ranges vary slightly by guideline. Values below 40% are considered severely reduced and are associated with heart failure with reduced ejection fraction (HFrEF). The range 40–49% is often called mildly reduced (or mid-range) ejection fraction.

Stroke volume and cardiac output give additional context. A low EF with a normal stroke volume can occur in a small ventricle, while a high EF with low stroke volume can occur in a dilated ventricle. Cardiac output depends on heart rate, so it is not a pure measure of contractility.

Common Mistakes and Pitfalls

• Mixing up end-diastolic and end-systolic values — EDV is always larger than ESV. If your EF comes out negative or over 100%, you have swapped them.
• Using monoplane volumes — If you only have one view, the biplane formula is not appropriate. Use the monoplane EF formula instead (EF = (EDV − ESV)/EDV × 100 with just one set of volumes).
• Entering volumes in different units — All four volumes must be in the same unit (mL). Mixing mL and L will give a nonsensical result.
• Rounding too early — If you round each volume to the nearest mL before calculating, the EF can shift by a point or two. Keep full precision until the final step.
• Ignoring tracing quality — The calculator is only as good as the volumes you feed it. Poor endocardial border definition, foreshortened apical views, or heavy trabeculation can make the volumes inaccurate regardless of the math.

Biplane vs. Other EF Methods

Besides biplane Simpson’s, there are several other ways to measure ejection fraction:

• Monoplane Simpson’s — Uses only one apical view. Faster but less accurate, especially when the ventricle is asymmetrical.
• Teichholz (M-mode) — Derives EF from a single linear dimension. Quick but assumes a normal shape; fails in regional wall motion abnormalities.
• Visual estimation (“eyeballingâ€�) — Experienced readers can be accurate, but it is subjective and varies between observers.
• 3D echocardiography — Uses a full 3D volume, avoiding geometric assumptions entirely. More accurate than biplane but requires special equipment and good image quality.
• Cardiac MRI — The gold standard for volumes and EF, but expensive, time-consuming, and not portable.

Biplane Simpson’s is the best compromise for routine clinical use: it is more accurate than monoplane or M-mode, but faster and cheaper than 3D or MRI.

Limitations of the Biplane Formula

The biplane method assumes the left ventricle can be represented as a stack of elliptical disks. This is a good approximation for most ventricles, but it fails in cases of severe aneurysm, extreme hypertrophy, or asymmetric remodeling. In those situations, 3D echo or MRI is preferred. The method also relies on accurate endocardial tracing, which can be difficult in patients with poor acoustic windows (e.g., obesity, COPD, chest wall deformities).

Finally, the volumes themselves are derived from a geometric model — they are not direct measurements. The true volume of a beating heart changes continuously, and the timing of “end-diastole� and “end-systole� is defined by the ECG or by visual inspection of the largest and smallest frames. Small timing errors can shift the EF by several percentage points.

Frequently Asked Questions

What is a normal ejection fraction?

A normal LVEF is generally 52–72% in men and 54–74% in women, depending on the guideline (ASE, ESC, etc.). Values below 40% are considered severely reduced. Your doctor will interpret your EF in the context of symptoms, other imaging, and blood tests.

Can I use this calculator for a single apical view?

No — this calculator is specifically for the biplane method, which requires both the four-chamber and two-chamber volumes. If you only have one view, use the monoplane formula: EF = (EDV − ESV)/EDV × 100 with the volumes from that single view. The result will be less accurate, but it is still a reasonable estimate.

Why did my echo report show a different EF than this calculator?

Echo software often applies automated border detection and may use a slightly different algorithm (e.g., monoplane, or a different disk count). Also, the sonographer may have traced the endocardium differently. Small differences of 1–3% are normal. If the difference is large, ask your doctor to review the raw images.

Does this calculator work for the right ventricle?

No — the biplane method of disks is designed for the left ventricle. Right ventricular EF is usually measured by 3D echo or MRI, as the right ventricle has a more complex shape that does not fit the elliptical disk model.

What if my volumes are in liters, not milliliters?

Convert liters to milliliters by multiplying by 1000 before entering them. For example, 0.11 L = 110 mL. If you enter liters directly, the EF will still be correct (because the units cancel), but stroke volume and cardiac output will be wrong by a factor of 1000.

Is ejection fraction the same as cardiac output?

No. Ejection fraction is the percentage of blood pumped out of the ventricle per beat. Cardiac output is the total volume pumped per minute (stroke volume × heart rate). A person can have a normal EF but low cardiac output if the heart rate is very low, or a low EF but normal cardiac output if the ventricle is dilated and the heart rate is high.

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in edv4 | EDV 4-chamber | mL | 112 | 0
in esv4 | ESV 4-chamber | mL | 45 | 0
in edv2 | EDV 2-chamber | mL | 108 | 0
in esv2 | ESV 2-chamber | mL | 42 | 0
in hr | Heart rate | bpm | 70 | 0
out ef | Ejection fraction | % | ((edv4+edv2)-(esv4+esv2))/(edv4+edv2)*100 | 1
out sv | Stroke volume | mL | ((edv4+edv2)-(esv4+esv2))/2 | 1
out co | Cardiac output | L/min | (((edv4+edv2)-(esv4+esv2))/2*hr)/1000 | 2