Harmony · Side view · Facial Profile
Z Angle
The angle between a chin-to-upper-lip line and the Frankfort reference direction.
What is measured
The calculation
Angle between pogonion–upper-lip and porion–orbitale directions
Side view / Measurement guide
Follow the measurement
Select a label to focus on its line. Select again to show all measurements.
In these guides, nasion means the nasal root, subnasale the nose base, and pogonion the most forward chin point. Frankfort refers to the direction from the ear-opening landmark to the lower orbital landmark.
Why it matters
It connects lip projection with chin position relative to a head reference. Moving either the upper lip or chin changes the line, so the result represents their relationship.
- A smaller angle means the two measured directions are closer together.
- A larger angle means they diverge more; inspect the lip and chin together.
Where the idea comes from
FaceIQ adaptation
Merrifield introduced the profile-line approach in 1966. The clinical Z-angle uses a line tangent to the chin and the most protrusive lip; FaceIQ specifically uses the upper-lip landmark. [1]
A worked example
A lip–chin line inclined 80° to the Frankfort direction produces an 80° result. A head-reference error can change the comparison.
Example values explain the calculation. They are not a target range and are not measurements of the schematic above.
Research & further reading
The sources below explain the history or related evidence. FaceIQ’s score weights and reference ranges are model settings; these papers do not collectively validate the scoring system.
[1] Merrifield · 1966
The profile line as an aid in critically evaluating facial estheticsHistorical source for the profile line and Z-angle. FaceIQ uses an upper-lip landmark for its photographic version.