Bigonial : bizygomatic width
Width of the lower face at the jaw angles divided by the widest facial width.
How to read it
the lower face tapers markedly relative to the cheekbones for the reference group.
jaw width relative to cheek width sits close to the reference mean (~0.70–0.75).
the lower face is comparatively wide relative to the cheekbones for the reference group.
Both landmarks are on the soft-tissue silhouette, not bone. Bigonial breadth from a 2D photo differs from direct measurement by 9.3 mm on average (Lim 2022) despite high repeatability. What is measured is the masseter + fat envelope, and it shifts with yaw. This is why the gonial angle itself is given as its photographic equivalent (jaw taper & definition) rather than in degrees.
Reference values by population
| Reference population | Female (mean ± SD) | Male (mean ± SD) | n | Source |
|---|---|---|---|---|
| North American White | 0.698 ± 0.053 | 0.698 ± 0.049 | 2326 | Farkas 1994/2005 (NA White young adults) prov. |
| East Asian | 0.728 ± 0.053 | 0.731 ± 0.05 | 618 | Farkas 2005 (Chinese/Japanese/Vietnamese/Thai pooled); Jayaratne 2012 (Southern Chinese, n=103) prov. |
| South Asian | 0.711 ± 0.054 | 0.721 ± 0.053 | 210 | Farkas 2005 (Indian); Metgudmath 2022 prov. |
| African / African diaspora | 0.705 ± 0.053 | 0.707 ± 0.051 | 300 | Farkas 2005 (African-American, Zulu, Angolan) prov. |
| Middle Eastern | 0.707 ± 0.053 | 0.71 ± 0.051 | 348 | Farkas 2005 (Turkish, Iranian, Egyptian); Al-Sebaei 2015 (Saudi, n=168) prov. |
| Hispanic / Latino | 0.71 ± 0.053 | 0.714 ± 0.051 | 120 | Farkas 2005 (Mexican-American) prov. |
| Not specified — show pooled | 0.71 ± 0.059 | 0.714 ± 0.057 | 3922 | Unweighted pool of the six groups above 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). For a typical 300 px inter-pupil photo that is ≈12 px per landmark, which is why small ratios and angles get wide intervals. A number without an interval is a number pretending to be more precise than it is.
References
- Farkas, Katic & Forrest (2005). International Anthropometric Study of Facial Morphology in Various Ethnic Groups/Races. J Craniofac Surg 16(4):615–646. doi.org/10.1097/01.SCS.0000171847.58031.9E
- Lim, Abdul Shakor & Shaharudin (2022). Reliability and Accuracy of 2D Photogrammetry: A Comparison With Direct Measurement. Front Public Health 9:813058. doi.org/10.3389/fpubh.2021.813058
Related: how bone-level measurements are taken from a photo · methodology · all insights