Measurement guide
Canthal tilt
The angle of the line from the inner corner of the eye to the outer corner. Positive when the outer corner sits higher, negative when it sits lower.
How it's measured
Each eye gets two points: the inner corner (endocanthion) and the outer corner (exocanthion), where the upper and lower lids meet. The tilt is the angle of the line through them against a horizontal reference.
The reference matters. Measured against the edges of the photo, a head rolled a few degrees to one side adds those degrees to one eye and takes them from the other. Measuring against the line through both inner corners cancels that roll, so the number describes the eye rather than how the phone was held. Each eye is measured on its own, because left and right are rarely identical.
Typical values
Most adults have a small upward tilt. In a photo study of 300 adults aged 18 to 26, the average was about 5° in men and 7° in women (Vasanthakumar et al., 2012). Averages differ between populations, and tilt changes with age: a study comparing younger and older adults found a clear difference in the slant of the eye opening between the groups (Liu et al., 2023).
Values near zero, and slightly negative ones, also occur in healthy adults. An average is a centre, not a cut-off.
How Harmony measures it
Eye corner tilt canthal tilt
For each eye: the angle between the line from the inner corner (endocanthion) to the outer corner (exocanthion) and the line through both inner corners. Positive when the outer corner sits higher. The value is the mean of both eyes; each eye is also listed on its own.
- Male reference
- 5–8.5°
- Female reference
- 6–9.5°
Range: Community facial analysis formula (public spreadsheet), top range: men 5-8.5°, women 6-9.5°. Counts toward the score with weight 30 (Community formula point table: canthal tilt, 30 points).
What changes the number in a photo
- Chin up or down. Tipping the head forward makes the outer corners look higher in a flat photo; tipping it back does the opposite. Keep the head level with the camera at eye height.
- Smiling or squinting. The cheeks push the lower lids up and move the corners. Use a relaxed, neutral face.
- Small or blurry photos. An eye corner is only a few pixels wide. On a small image, moving a point by one or two pixels can change the angle by a degree, so zoom in and check both corners.
One number, one feature
Canthal tilt is a single angle on a single feature, and it moves with expression and age. It describes the geometry of the eye opening in one photo, nothing more.