Measurement reference · FaceFluent editorial · September 13, 2026
Mouth width to nose width
The width of the mouth divided by the width of the nose. The canon sets it at roughly one and a half.
Also called naso-oral ratio, mouth width to nose width.
Reference range
None.
Historical drawing canons provide context for this proportion. We do not display a numerical target band or treat those canons as population norms.
How we calculate it
Distance between the two mouth-corner landmarks over the distance between the two nostril-edge landmarks.
What moves the number
Expression, more than anything. A closed neutral mouth and a slight smile give different answers on the same face in the same minute.
What it cannot tell you
Again a convention rather than a norm. The same 1985 survey found the horizontal canons matched a minority of real faces. A difference from that convention does not establish that a mouth is too wide or too narrow.
References
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