Gonial Angle (Jaw Angle)
The gonial angle is the angle at the corner of the jaw, where the vertical ramus meets the horizontal mandibular body — measured in degrees.
Definition
The gonial angle (also called the angle of the mandible) is formed at the gonion — the bony corner where the vertical ramus of the mandible meets the horizontal body. Measured cephalometrically, the angle is typically reported in degrees, with 90° representing a perfect right angle and higher values representing a more obtuse, rounded jaw. Adult averages run 120°-130° in young men, 125°-135° in young women, with modest widening (more obtuse) over the lifespan. A sharper gonial angle (closer to 120°) reads as defined, masculine, and angular. A wider angle (above 145°) reads as soft, round, or older. The gonial angle is one of the single most studied jaw metrics in orthodontics and facial aesthetics.
Why it matters
The gonial angle is the main driver of how defined a jaw looks in profile. The bone changes only with surgery, but the angle a photo shows is partly modifiable: body fat reduction along the jawline and head posture can both produce a sharper-looking angle even when the bone itself is unchanged. Gum chewing is weaker evidence than it sounds: in a six-month randomised trial, masseter thickness and jaw shape did not change.
How AI measures it
On a side-profile photo or a cephalometric X-ray, the gonial angle is the angle between the ramus line (gonion to ear) and the mandibular body line (gonion to chin), reported in degrees. A front-facing photo cannot show the ramus, so the angle is not measured from a front photo. From the front, the RealSmile scan reads jaw shape through jaw taper (jaw width against cheekbone width) and chin proportion instead.
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Frequently asked questions
What is an ideal gonial angle?
For men, 120-130° is the elite range. For women, 125-135° is more typical and considered ideal. Above 145° reads as soft or rounded. Below 115° is rare and starts looking surgically sharp.
Does gonial angle change with age?
Yes. The angle tends to widen with age, due to bone remodeling and dental changes. Tooth loss accelerates the change significantly.
Can mastic gum sharpen the gonial angle?
It works the masseter, but in a six-month randomised trial of daily gum chewing, masseter thickness and jaw shape did not change. The bone itself doesn't change either; body fat and head posture move how the angle reads far more.