Interpupillary ratio
The distance between your pupils relative to your face width.
Why it matters
Pupil spacing is a core "averageness" cue; large deviations are quickly noticed.
What interpupillary ratio measures
Interpupillary ratio is the distance between the centres of your two pupils, measured from the iris centres, expressed as a fraction of your face width. The raw pupil-to-pupil distance is the same quantity an optician records as your PD when fitting glasses; here it is divided by the cheekbone width so it describes proportion rather than an absolute span in millimetres.
It is closely related to eye spacing but not identical: eye spacing measures the gap between the inner corners, whereas this metric measures from pupil to pupil, so it folds in both the gap and the position of the eyes within their openings.
Why pupil spacing matters
Pupil spacing is a core averageness cue: it sits at the very centre of the face, and large departures from the typical proportion are noticed quickly even by an untrained eye. Because it anchors the horizontal balance of the whole face, it features in the classical proportion canons. Farkas 1994 is the anthropometric reference used here.
Averageness in this sense means closeness to the population typical, which research has linked to perceived harmony; it is not a statement that an average face is the only attractive one, and it carries no judgement of worth. The practical upshot is that pupil spacing rarely stands out on its own unless it is well away from the norm, and even then it is read in the context of the surrounding features rather than in isolation.
Typical range and its caveats
The commonly cited balance point is around 0.46 of face width, and the scored band runs from about 0.44 to 0.49, with a mesh average near 0.455. One honest limitation is that the measurement relies on the refined iris landmarks, which are less precise than the broader face-oval points, so the figure should be read as approximate rather than exact.
Pupil spacing also varies normally between people and across populations, and like the other proportion canons it is a convention rather than a law. A value a little outside the band is common and unremarkable.
Interpreting your number and what can change it
Use a front-on, level photo so that head rotation does not distort the apparent distance between the pupils. Because the landmarks are approximate, put more weight on clear, large deviations than on small ones near the band edge.
This is among the most fixed of all the metrics. Pupil spacing is set by the position of the eyes in the bony orbits and is not something grooming, makeup or cosmetic surgery meaningfully changes; the realistic lever is only how the surrounding face is framed. If you need the figure for a practical purpose such as ordering glasses, your optician's measured PD is the right source.
Typical range
~0.46 of face width
Distance between the pupils (iris centers) relative to face width. Near 0.46 is a commonly cited balance point.
What your reading means
- Typical
- Your pupil spacing is well proportioned to your face.
- Less common
- Your pupil spacing is slightly off the typical proportion.
- Distinctive
- Your pupil spacing is relatively wide or narrow for your face.
How we measured it
We measure pupil-to-pupil distance (from the iris centres) and divide by your cheekbone width.
The evidence
Uses the refined iris landmarks, which are less precise than the face-oval points — treat as approximate.
References
- Farkas, L. G. (Ed.). (1994). Anthropometry of the Head and Face (2nd ed.). New York: Raven Press.