Mouth corner tilt
Oral commissure tilt
Whether the corners of the mouth point up or down: the angle of the line between them against the line joining the pupils, plus how high the corners sit relative to the middle of the lips.
Also searched as oral commissure tilt, downturned mouth corners and upturned mouth.
How to read it
the corners of the mouth sit below the lip midline at rest (downturned commissures). This is strongly age- and expression-dependent.
the mouth corners sit approximately level with the lip midline.
the corners of the mouth sit above the lip midline at rest.
A residual smile of even a few percent (see blendshape values in capture quality) shifts this by several degrees.
Reference values by population
| Reference population | Female (mean ± SD) | Male (mean ± SD) | n | Source |
|---|---|---|---|---|
| North American White | +0° ± 3.5 | +0° ± 3.5 | — | Neutral-expression convention: level commissures ≈ 0°; no population table available prov. |
| East Asian | +0° ± 3.5 | +0° ± 3.5 | — | Neutral-expression convention: level commissures ≈ 0°; no population table available prov. |
| South Asian | +0° ± 3.5 | +0° ± 3.5 | — | Neutral-expression convention: level commissures ≈ 0°; no population table available prov. |
| African / African diaspora | +0° ± 3.5 | +0° ± 3.5 | — | Neutral-expression convention: level commissures ≈ 0°; no population table available prov. |
| Middle Eastern | +0° ± 3.5 | +0° ± 3.5 | — | Neutral-expression convention: level commissures ≈ 0°; no population table available prov. |
| Hispanic / Latino | +0° ± 3.5 | +0° ± 3.5 | — | Neutral-expression convention: level commissures ≈ 0°; no population table available prov. |
| Not specified — show pooled | +0° ± 3.5 | +0° ± 3.5 | — | Neutral-expression convention: level commissures ≈ 0°; no population table available prov. |
Where these numbers come from
Transcribed from the cited anthropometric literature; SDs of ratios are propagated conservatively (independence assumed). Entries marked prov. await line-by-line audit against the primary tables. See the norm provenance note.
Why every value has an error bar
Every value Canthion reports carries a 1σ uncertainty propagated from MediaPipe Face Mesh's published accuracy (3.96% of inter-ocular distance mean absolute error per landmark, Kartynnik 2019). On a typical photo with 300 px between the pupils, that is about 12 px of wander on every point. Small ratios and angles inherit it, so their intervals are wide. A number without an interval is a number pretending to be more precise than it is.
References
- Kartynnik, Ablavatski, Grishchenko & Grundmann (2019). Real-time Facial Surface Geometry from Monocular Video on Mobile GPUs. arXiv:1907.06724. arxiv.org/abs/1907.06724
Common questions
What is mouth corner tilt?
Whether the corners of the mouth point up or down: the angle of the line between them against the line joining the pupils, plus how high the corners sit relative to the middle of the lips. Positive = corners higher than the midline.
How is mouth corner tilt measured from a photo?
It is computed from the face-mesh landmarks (ch_R, ch_L, sto): atan2(mean(ch.y) − sto.y, mouthWidth/2) relative to IPD line. Every value carries a 1σ error bar propagated from the landmark detector's published accuracy, with a floor of ± 1.5°, so a small difference inside the interval is not a difference.
What is a normal mouth corner tilt?
Across the reference populations the anatomical norm is the same: +0° ± 3.5 for women, +0° ± 3.5 for men. This value is provisional and awaits line-by-line audit against the primary tables. Your own value is placed on the distribution you choose, as a percentile with its error bar.
What does a low or high mouth corner tilt mean?
Below the mean: the corners of the mouth sit below the lip midline at rest (downturned commissures). This is strongly age- and expression-dependent. Above the mean: the corners of the mouth sit above the lip midline at rest.
How reliable is mouth corner tilt from a photograph?
A residual smile of even a few percent (see blendshape values in capture quality) shifts this by several degrees.
Related measurements
The rest of the lips set, then the nearest measurements elsewhere on the face. Every one is computed on the same photograph, in the same run, with its own error bar.
Also: how bone-level measurements are taken from a photo · methodology · glossary · all 35 insight pages