Mouth-to-nose width ratio

The mouth usually extends beyond the nasal wings, broadening the centre of the face below the nose. When the spans are closer in width, that expansion becomes less noticeable and the nose can look more prominent beside the mouth.

Changing either feature changes the comparison. A narrower nose can make an unchanged mouth look wider, while a broader mouth can create the same increase in the ratio.

A low ratio may reflect a broad nasal base above a mouth of ordinary width. If the mouth still occupies a substantial span beneath the pupils, the nose contributes more to the contrast. A modest nasal base above a narrow mouth creates a different arrangement: the oral span is small beside the feature above it.

At a high ratio, a wide mouth extends farther beyond the nose. A fine nasal base can also produce a high result without an unusually broad mouth. Comparing both features with the face helps distinguish a prominent mouth from a nose that is simply narrow.

Both spans can increase together while their ratio stays similar. The nose-mouth pair then occupies more of the centre, even though the local relationship between them is unchanged.

A narrow mouth can remain prominent when the lips show substantial height. A wider mouth with little visible lip height may look more understated, despite reaching farther across the face. Mouth width and lip fullness therefore contribute differently to the appearance beneath the nose.

The shape within the lips matters too. A tall lower lip adds visible area below the mouth seam, while a defined Cupid's bow makes the upper border more distinct.

The philtrum separates the upper lip from the nasal base. A short interval groups the nose and mouth closely together; a longer interval leaves more skin between them. The same width contrast can consequently appear within a compact central region or across a more extended one.

Mouth-to-pupil width helps assess whether the oral span is narrow beyond its comparison with the nose. If the mouth is narrow beneath the pupils as well, check whether pupil spacing is unusually broad. Widely spanning eyes can make an ordinary mouth look small beneath them.

Nose-to-face width adds the corresponding check for the nasal base. A high nasal fraction alongside a substantial mouth-to-pupil span points towards nasal breadth as the main contrast. A modest nasal fraction alongside a narrow oral span makes mouth width a more likely contributor.

The jaw and chin frame the mouth from below. A wide mouth above a broad chin continues the horizontal breadth, while the same mouth above a narrow chin creates more narrowing towards the bottom. This can change how expansive the mouth looks even when its relationship with the nose stays fixed.

The traditional 1.5 relationship is a neoclassical proportional canon. It describes a mouth half again as wide as the nasal base, rather than an optimum established by comparing every nearby value.

Torsello and colleagues found mouth widths exceeding 150% of nasal width in their selected Italian female models. The professional Black-model study cited below reported a different central tendency.

Population variation is especially relevant to nasal breadth. Fang, Clapham and Chung documented differences across reference groups, so a single local ratio may represent a common arrangement in one sample and a less common one in another.

Nasal and oral dimensions develop at different rates, allowing their width relationship to change as the face matures. In adulthood, mouth width and visible lip height can also change differently. Sforza and colleagues found reduced vermilion height relative to mouth width with age, so a wider-looking mouth may have less vertical fullness.

Changes in nasal width can offset changes in mouth width, leaving the ratio similar while the surrounding contours look different. Earlier photographs are most informative when the expression and camera distance are comparable.

Smiling can widen the mouth and nasal base together. Use relaxed lips when comparing results, and place the mouth points at the corners where the lips meet. The nasal points belong on the outer wings rather than the nostril openings.

A close camera can make the nose appear larger relative to the mouth. Keep the camera distance consistent and face it straight on so both widths are seen from the same angle. Inspect the sides separately too: an uneven mouth or nasal outline can preserve the same total span.