Interpupillary distance: the number behind eye separation ratio, and a scale reference in its own right.

Interpupillary distance (IPD) is the straight-line distance between the centers of the two pupils, reported as a single number in millimeters:

• Narrower IPD — discussed in forum tiers as reading closer to a hypotelorism label at the low end.
• Wider IPD — discussed in forum tiers as reading toward a hypertelorism label at the high end.

That's different from eye separation ratio, which divides this same interpupillary distance by bizygomatic width to produce a proportion. IPD on its own is an absolute length, not a ratio between two widths.

Looksmax.org poll threads commonly cite a tier ladder: roughly 57.5mm and under as hypotelorism, a 64-66mm band as male average, up to roughly 72.5mm and above as hypertelorism, with several bands in between.

Clinical sources define hypertelorism and hypotelorism using bony orbit spacing, and use telecanthus for a separate condition affecting the inner eye corners — not pupil centers. Forum tiers borrow the clinical vocabulary but apply it to a different landmark, so a self-measured IPD number and a clinical diagnosis are not the same claim.

Any absolute length in millimeters needs a real-world scale reference, since a single flat photo at an unknown distance can't resolve one on its own. Interpupillary distance has a specific wrinkle beyond that general problem:

• Photogrammetry and AR tools that convert pixels to millimeters often need exactly this kind of reference — and an assumed average adult IPD of roughly 63mm is one of the most common references used for that purpose, since it's stable across a face and doesn't require an external object in frame.
• A tool built on that assumption cannot also independently report a personal IPD as its output: the number handed back reflects the constant it assumed, not a measurement of that individual's actual eyes.

So a printed IPD figure from a photo tool is worth checking for whether IPD was the tool's scale input or its measured output — it's rarely honestly both.

Mogalytics does not compute or display an absolute interpupillary distance in millimeters. The closest existing pages are:

• Eye separation ratio — divides this same interpupillary distance by cheek width, which sidesteps the millimeter-scale problem entirely.
• Canthal tilt — the other eye-region measurement Mogalytics reads live, an angle rather than a length.

Mogalytics makes no claim that either measurement approximates a personal interpupillary distance in millimeters, or of parity with any other site's specific IPD calculation.

Interpupillary distance is the raw figure behind one of the six measurements Mogalytics tracks, and shares its scale problem with one other page on this site:

• Eye separation ratio — the same interpupillary distance, expressed as a ratio against cheek width instead of an absolute length.
• Canthal tilt — the other eye-region measurement Mogalytics reads live.
• Philtrum length — another absolute mm figure with the same monocular scale-ambiguity limitation.
• Hunter eyes vs prey eyes — a broader eye-region label this measurement is often folded into.
• How does Omoggle's scoring work? — the publicly described mechanics this term shows up alongside.