Start your free eye size symmetry measurement scan
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478 landmarks
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Left vs right palpebral aperture
Eye symmetry test: is one eye bigger than the other?
Almost everyone has one eye that reads as slightly larger or more open than the other, and this is normal. This free eye symmetry test uses an AI face scan to measure the visible opening of each eye from 3D landmarks and reports the difference so you can see whether it sits within the typical range.
Free basic reports require no credit card, no account, no password. Your image is never uploaded or stored. Analysis happens in your browser and your session data is cleared when you close or refresh the page.
In short
An eye size symmetry test compares the palpebral aperture, the visible eye opening, on the left and right side of your face. Facemap measures the area and vertical height of each eye from landmark data and reports the percentage difference between them.
- 3D landmarks
- 4783D landmarks
- Scan time
- ~20sScan time
- Uploads, runs in browser
- 0Uploads, runs in browser
- No account required
- FreeNo account required
Where it is measured
Eye size symmetry on the landmark mesh.
The overlay is drawn from the same 478 point MediaPipe landmark set Facemap uses on your own scan, so every caliper, axis and node sits on the exact anatomy the measurement is taken from.
Sample reading, Left vs right palpebral aperture
- Left aperture
- 268 mm²
- Right aperture
- 259 mm²
- Area delta
- 3.4%
- Height delta
- 0.6 mm
How the scan works
Capture
Guided front-on frame with even light, no upload.
Landmark
478 point mesh placed on your face in real time.
Report
Eye size symmetry measured, normalised and explained.
What is eye size symmetry?
Eye size symmetry describes how closely the left and right palpebral apertures, the open area between your upper and lower eyelid, match in area and height when the face is at rest.
How Facemap measures eye size symmetry
The mesh places landmarks around the upper and lower eyelid margin of each eye. Facemap calculates the enclosed area and the maximum vertical height for each eye, then reports the percentage difference between left and right, normalised to your eye width.
What the typical range looks like
A small difference between the two eyes is near universal and is rarely noticeable in daily life. The reading is most useful as a description of your own structure, not as a comparison against anyone else's face.
How to read your result
Facemap reports separate area and height figures for each eye so you can see whether the difference is driven by aperture height, which often relates to eyelid position, or by overall shape. Lighting and gaze direction can shift the reading, so repeat scans under consistent conditions are more reliable than a single result.
The eye size symmetry formula: how we calculate it
Difference in aperture openness between the two eyes. Landmark numbers are MediaPipe Face Landmarker indices, and every distance is normalised to your own face so camera distance and image size cancel out.
|EAR(left) - EAR(right)| / mean EAR, where EAR = eye height / eye width
- Landmarks used
- 33, 133, 145, 159 and 263, 362, 374, 386
- Reference target
- 0, identical openness
- Tolerance band
- 0.20
Your reading is compared with that published reference on a Gaussian match curve: score = round( 100 x exp( -0.5 x ( (reading - target) / tolerance )^2 ) ), clamped to 1 to 99. Basis for the reference value: openness is compared rather than raw area so a few degrees of head turn does not register as asymmetry. The headline Attractiveness Score works differently: all readings are corrected for head angle and expression, weighted by confidence and mapped onto a 1 to 100 scale by a model calibrated against a published research set of more than Facemap scans.
Read the full Facemap methodology, including how the 22 measurement categories combine into your Attractiveness Score.
Eye size symmetry reference table
Eye size difference bands and how each one reads.
- 0 to 5%Very close match
Difference below the visible threshold
- 5 to 10%Typical
Common and rarely noticeable
- 10 to 18%Noticeable
Visible on close inspection or in photos
- Above 18%Marked
Consistently visible difference in size
What causes one eye to look bigger than the other?
Uneven eye size usually reflects small, lifelong differences in bone and soft tissue rather than any single cause. A few common contributors:
- Natural asymmetry in eyelid position and crease height
- Slight difference in brow height on one side
- Minor skeletal asymmetry around the eye socket
- Fatigue or fluid retention, which can shift readings day to day
- Habitual expression or sleeping position over many years
How to get an accurate eye symmetry reading
Eye aperture is sensitive to gaze and lighting, so the following conditions keep repeat scans comparable.
- Look directly at the camera, not off to one side
- Keep both eyes open naturally, no squinting
- Use even light with no shadow across one side of the face
- Remove glasses so the eyelid margin stays visible
- Keep hair and fringe clear of both brows
Why minor eye asymmetry is not a concern
Population studies of facial landmarks consistently find small left to right differences in eye size across almost all faces. The difference is part of normal human variation and is not, on its own, a marker of anything else. Facemap reports the figure as a structural description and does not offer any medical interpretation.
The eye size symmetry formula, step by step
The underlying formula is simple arithmetic applied to landmark data from the AI face scan: the left eye's palpebral aperture area is divided by the right eye's palpebral aperture area, and the result is expressed as a percentage difference so a positive figure means the left eye is larger and a negative figure means the right eye is larger.
- Place landmarks around the eyelid margin of each eye
- Calculate the enclosed area of the left eye opening
- Calculate the enclosed area of the right eye opening
- Divide left area by right area to get a raw ratio
- Convert the ratio to a percentage difference, positive or negative
- Normalise the result to your own eye width for comparability
Your reading
Measure your eye size symmetry in about twenty seconds.
The scan runs in your browser. Nothing is uploaded, and free basic reports need no account.
Questions
Eye symmetry test: frequently asked questions
Is it normal for one eye to be bigger than the other?
Yes. Small differences in eye size between the left and right side are extremely common and are found across almost all faces when measured precisely.
How is eye size symmetry measured?
Facemap places landmarks around the eyelid margin of each eye using MediaPipe Face Mesh, then compares the enclosed area and vertical height between the left and right eye.
Can eye size symmetry change over time?
The underlying bone and eyelid structure is stable, but the reading can shift slightly with fatigue, fluid retention or gaze direction at the moment of capture.
Do I need to upload a photo for the eye symmetry test?
No. The free scan runs entirely on your device using your camera, and nothing is uploaded to a server.
What is considered a large eye size difference?
Differences above roughly 18% between left and right aperture area are consistently visible, while most measured faces fall below 10%.
What formula does the eye size symmetry calculator use?
The calculator divides the left eye's aperture area by the right eye's aperture area, then converts that ratio into a percentage difference. A positive figure means the left eye reads larger, a negative figure means the right eye reads larger.
How does the AI face scan actually work?
The AI face scan runs Google's MediaPipe Face Mesh, a machine learning model, entirely in your browser. It places 478 3D landmarks on your face and nothing is uploaded. The result is deterministic geometry calculated from those points, not an opinion or a guess.
Related tools
Measurements that read alongside eye size symmetry.
Eye-axis inclination angle
Canthal tilt face scan
The upward or downward angle of the eye's outer corner relative to its inner corner, measured from the same 3D landmark set.
Height, arch and left/right balance
Brow symmetry face scan
We measure brow height, the horizontal position of the arch peak, and compare both readings between your left and right brow to score overall brow balance.
Palpebral fissure width vs height
Eye aspect ratio face scan
We measure the width and height of the visible eye opening, the palpebral fissure, and use the relationship between them to describe eye shape as almond, round or narrow.
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