Measurement guide
Eye separation ratio (ESR)
The distance between the centres of the pupils divided by the width of the face. It describes how far apart the eyes sit relative to the face around them.
How it's measured
Mark the centre of each pupil and the widest points of the face at the cheekbones (zygion, the outermost point of each cheekbone arch). Divide the pupil distance by the cheekbone width. Both lengths come from the same photo, so the photo's scale cancels out and no ruler is needed.
Not every source uses the same face width. Some measure between the ears or at the jaw instead of the cheekbones, which gives a different number for the same face. Check the definition before comparing your ESR with a value from somewhere else.
Typical values
In adults the pupils sit about 63 mm apart on average, roughly 65 mm in men and 62 mm in women (Dodgson, 2004).
In a study of attractiveness judgements, photos of women's faces were rated highest when the pupil distance was about 46% of face width, which was also close to the average of the faces the researchers measured (Pallett, Link & Lee, 2010). That study took face width between the inner edges of the ears rather than at the cheekbones, so its 46% isn't directly comparable with an ESR measured at the cheekbones.
How Harmony measures it
Eye spacing ESR
Distance between the pupil centres divided by the width across the cheekbones (zygion to zygion), as a percentage.
- Male reference
- 44.3–47.7%
- Female reference
- 45–47.9%
Range: Community facial analysis formula (public spreadsheet), top range: men 44.3-47.7%, women 45-47.9%. North American norms give about 46% for men (North American young-adult norms: Farkas LG, Katic MJ, Forrest CR. Ann Plast Surg 2007;59:692-698, as tabulated by Virdi SS, Wertheim D, Naini FB. Maxillofac Plast Reconstr Surg 2019;41:9). Counts toward the score with weight 35 (Community formula point table: eye separation ratio, 35 points).
How Harmony measures it
Pupil distance IPD
Distance between the pupil centres in millimetres. The scale comes from the iris, which is close to 11.7 mm across in adults, so the value only appears when the detector measured the irises.
- Male reference
- 61–68 mm
- Female reference
- 59–66 mm
Range: About one standard deviation around the adult means of 64.7 mm (men) and 62.3 mm (women) in Dodgson NA. Variation and extrema of human interpupillary distance. Proc SPIE 2004;5291:36-46. Shown for information. It isn't part of the score.
What changes the number in a photo
- Camera distance. At arm's length, perspective makes the middle of the face look bigger next to its outer edges; a modelling study found the nose reads about 30% larger relative to cheekbone width at 30 cm than from far away (Ward et al., 2018). Stand about 1.5 m away and zoom in.
- Head turn. Turning even slightly narrows one side of the face and shifts the pupils. Face the camera squarely.
- Gaze. Looking off to the side moves the pupils. Look into the lens.
- Hair. Hair over the sides of the face hides the cheekbone outline. Tuck it back.
One number, one feature
ESR compares two widths. Eye shape, lids and brows change how spacing looks, and none of them is in the ratio.