Mouth-to-nose width ratio explained

What mouth-to-nose width ratio is

The mouth-to-nose width ratio compares the width of your mouth, from corner to corner, with the width of the base of your nose. A mouth clearly wider than the nose reads balanced. A mouth about as wide as the nose reads compact, and a very wide mouth reads broad and expressive.

The measure matters mostly as a way to understand the lower half of your face in context. It is also one of the measures most affected by expression, since a smile stretches the mouth sideways.

In the LookFlex app this measurement appears as Mouth-to-nose width.

How LookFlex measures it

LookFlex measures the distance between the two corners of the mouth, and divides it by the distance between the outer edges of the nostril base. Both are horizontal widths, so the ratio is unaffected by image size.

Because the mouth corners move so easily, the number comes with a lower baseline confidence than structural measures such as eye spacing. A neutral, closed mouth gives the most repeatable result.

The calculation: ratio = mouth width ÷ width of the nose base.

Landmarks used

LookFlex reads these points from the 478-landmark face mesh. The numbers are each point's index in that mesh.

• Mouth corners: 61, 291
• Outer edges of the nostril base: 129, 358

The full pipeline, including how pose and mirror-averaging reduce noise, is on how LookFlex measures your face.

Typical and scoring ranges

LookFlex shows two ranges. The typical range is the middle half of its reference set, from the 25th to the 75th percentile: half of the faces fell inside it. The scoring range is where a reading earns a closeness score of 100; outside it the score falls smoothly, with no cliff at the edge. Both differ for men and women, and LookFlex blends the two if you choose Other or prefer not to say. Unit: unitless ratio.

How to read your result

"The range" here means the scoring range. The impressions below are common styling descriptions, not research findings. What research does show is in the next section.

• Below the range: The mouth is compact relative to the nose. A defined lip line keeps it balanced.
• Inside the range: Mouth and nose widths sit inside the scoring range.
• Above the range: The mouth is wide relative to the nose: an expressive, broad smile.

What the research says

Limited evidence We found no study of this ratio, so it rests on styling convention.

• Real faces vary widely in their proportions (Farkas et al., 1985).
• Close-up photos distort the nose, which is the denominator of this ratio (Ward et al., 2018).
• LookFlex's range is calibrated on its own reference set and is not drawn from a published norm.

No study we cite tests LookFlex's own ranges. They come from the calibration described on the methodology page, and every source is listed under References below.

What influences it

Mostly fixed

• The width of the mouth opening and the width of the nose, both anatomical.
• Age, which can change the mouth corners.

Things that move the reading

• Expression. A smile widens the mouth immediately, and pursed lips narrow it.
• Lip colour and liner, which change where the lips appear to end.
• Facial hair around the mouth, which changes the visual width.
• Camera distance, which exaggerates the nose and narrows the ratio.

How to improve how it reads

These suggestions change how the measurement reads or how well the photo captures it. Styling tips are common practice rather than tested in research, and none of them promises a change in bone structure.

• Scan with a relaxed, closed mouth. Do not smile and do not purse your lips.
• Use lip liner or a colour that follows your natural lip line to define a compact mouth.
• A moustache shape or beard line can widen or narrow the look of the mouth.
• Hold the camera at arm's length to avoid enlarging the nose.

Common myths

Myth: A wider mouth is always better.

A wider mouth reads expressive and a narrower one reads refined. The range of 1.28–1.46 for men and 1.36–1.55 for women marks a balance and not a goal.

Myth: Fillers or DIY injections are a safe way to change lip or mouth proportions.

DIY fillers and self-injection are unsafe and LookFlex never recommends them. If you are curious about a procedure, consult a board-certified professional first.

How it feeds your score

This measurement is one input to one sub-score, which then combine into your Glow Score:

• Harmony: 10% of the sub-score. Harmony carries 22% of the Glow Score.

Precision. Every reading of this measurement comes with a 95% margin, estimated by measuring your photo three times. Across the reference set the median margin was ±0.034: a retake in similar conditions usually lands within that much of the first reading. A change between two scans counts as real only when it is bigger than both scans' margins combined.

Confidence. LookFlex starts this measurement at a confidence of 75% and lowers it when your head angle, the lighting or image quality weakens the reading. The weight of each input in a sub-score scales with its confidence. Details are on the methodology page.