Eye separation ratio: two widths, measured at different depths.

Eye separation ratio compares interpupillary distance against bizygomatic width — the distance across the face at cheekbone level:

• Lower ratio — eyes read closer-set relative to the width of the face.
• Higher ratio — eyes read wider-set relative to the width of the face.

It's a proportion between two horizontal widths measured at different points on the face — one at the pupils, one at the cheekbones — not a size in absolute units and not a measurement of eye shape itself.

The two widths ESR divides sit at different depths on the face, which is exactly the kind of measurement a static photo struggles with:

• Pupil centers sit further back than the cheekbone plane, so turning the head even slightly off-axis foreshortens one width before the other and shifts the ratio.
• Camera distance and lens distortion compress or stretch both widths unevenly — a slider or typed-number calculator built from one photo has no way to correct for either.

That's the same underlying accuracy problem covered in the full breakdown of why face-rating scores swing between scans — pose, distance, and lens all move the number without moving the face.

Mogalytics does not compute or display a separate eye separation ratio number. Its six-measurement composite reads live from a front-facing camera feed, and the closest measurement sharing part of the same axis is:

• Cheekbone ratio — uses the same bizygomatic cheek-width measurement ESR divides by, but compares it against jaw width, not interpupillary distance.

Cheekbone ratio and ESR share one width axis but answer different questions — one compares cheek width to jaw width, the other compares eye spacing to cheek width. Mogalytics makes no claim of parity between the two, or with any other site's specific ESR calculation.

ESR shares its cheekbone-width axis with one of the six measurements Mogalytics tracks, and its eye-region focus with another. If you're auditing the rest:

• Cheekbone ratio — shares ESR's cheek-width measurement, compared against jaw width instead of eye spacing.
• Canthal tilt — the other eye-region measurement Mogalytics reads live, an angle rather than a width proportion.
• Facial width-to-height ratio (FWHR) — another widely searched proportion Mogalytics doesn't compute directly.
• How does Omoggle's scoring work? — the publicly described mechanics this term shows up in.