Harmony & facial ratios
Mouth & lips: the six measurements
6 min read · Updated November 1, 2026
Six measurements cover the mouth and lips: width against the nose and the eyes, the balance between upper and lower lip, the depth of the cupid's bow, the tilt of the mouth corners, and the chin-to-philtrum balance.
How these fit together
Two of these are in millimetres rather than ratios: cupid's bow depth and mouth corner position. A photo has no absolute scale, so the distance between the pupils, taken as 63 mm, converts pixels to millimetres. For a face far from that average the absolute figures are a little off, but they stay consistent between your own photos. Expression matters most in this group: a smile, a pout or parted lips change nearly every row.
A worked example
Suppose the pupils are 180 px apart in the photo. At 63 mm that makes one pixel 0.35 mm. If the dip of the cupid's bow sits 9 px below the line through its two peaks, the depth is 9 × 0.35 = 3.2 mm.
| Quantity | Value |
|---|---|
| Pupil distance | 180 px = 63 mm |
| Scale | 0.35 mm per px |
| Bow depth, 9 px | 3.2 mm |
Illustrative numbers, not a real person.
Mouth Width to Nose Width
The width of the mouth divided by the width of the base of the nose.
What it is
Mouth width to nose width is a classic proportion: the mouth is traditionally about one and a half times as wide as the nose. It describes how the lower features relate to each other.
How it's measured
Mouth width runs between the two mouth corners; nose width is across the outer nostril wings. The value is mouth divided by nose.
Definition: mouth width from corner to corner, divided by the width across the outer nostril wings.
How it's read
A mouth clearly wider than the nose reads balanced, with ranges set separately for men and women. A mouth barely wider than the nose can look small, and a very wide mouth can dominate the lower face.
What affects it
Even a slight smile widens the mouth and changes this ratio, so a neutral closed mouth is essential. Nostril flare affects the nose half of the ratio.
Interpupillary-Mouth Width Ratio
The width of the mouth compared with the distance between your pupils.
What it is
This relates the lower face to the eyes. It divides the width of the mouth by the distance between the pupils, so it shows whether the mouth is narrow or wide relative to the eye line.
How it's measured
Mouth width between the two corners is divided by pupil distance, both taken in a levelled frame.
Definition: mouth width from corner to corner, divided by the distance between the pupils.
How it's read
On most faces the mouth is somewhat narrower than the pupil gap, at about four fifths of it. A noticeably higher figure means a wide mouth for the eye spacing, and a lower one a small mouth.
What affects it
As with every mouth ratio, expression is the main distortion. A relaxed, closed mouth gives a repeatable result, and shooting from a normal distance avoids wide-angle stretching.
Lower Lip to Upper Lip Ratio
The height of the lower lip compared with the height of the upper lip.
What it is
This compares the vertical fullness of the two lips. The lower lip is usually fuller than the upper, and a common reference is a lower lip around one and a half times the height of the upper.
How it's measured
Upper lip height runs from the peaks of the cupid's bow down to the lip line, and lower lip height from the lip line to the lower lip's edge. The value is lower divided by upper.
Definition: the height of the lower lip divided by the height of the upper lip, both measured vertically from the lip seam, the upper lip from the peaks of its bow.
How it's read
A lower lip somewhat fuller than the upper reads naturally balanced, and the female range allows a fuller lower lip. A ratio near 1 means evenly full lips; much higher means a thin upper lip.
What affects it
Lip colour, lip balm shine, pursing or pressing your lips together all change where the edges fall. A relaxed mouth in even light measures best.
Cupid's Bow Depth
How far the dip in the middle of the upper lip sits below the two peaks of the bow.
What it is
The cupid's bow is the double curve on the upper lip, with a dip in the middle between two peaks. Its depth is how deep that dip is, in millimetres.
How it's measured
The depth is the vertical distance from the line joining the two peaks down to the midline dip. It is converted to millimetres by assuming an average pupil distance, so the value is a scale estimate rather than a caliper measurement.
Definition: the vertical distance, in millimetres, from the two peaks of the bow down to the dip at the midline. Pixels become millimetres using the pupil distance as the scale.
How it's read
A moderate, defined bow reads as a clear upper lip shape. A very flat bow looks soft and a very deep one pronounced. It is a fine detail, so it carries limited weight.
What affects it
Because the depth is only a few millimetres, small landmark errors matter. Sharp focus, even light and a closed relaxed mouth make a real difference; lip shine and shadows blur the bow.
Mouth Corner Position
Whether the corners of your mouth sit above or below the centre of your lip line.
What it is
Mouth corner position describes the natural tilt of the mouth: corners slightly above the centre give a gentle upturn, level corners are neutral and corners below the centre give a downturned, sad or tired look.
How it's measured
The height of the two mouth corners is compared with the midpoint of the lip line, in millimetres using the average pupil-distance scale. Positive means the corners sit above the centre.
Definition: the vertical offset, in millimetres, between the centre of the lip seam and the mouth corners. Positive when the corners sit above the centre.
How it's read
A neutral to slightly upturned mouth reads as pleasant and approachable. A strongly downturned mouth can read as stern or tired, though it is partly a resting-expression effect.
What affects it
This is the most expression-driven ratio of all: a tense jaw, a held smile or a frown change it immediately. Relax your face, let your mouth rest closed and retake if you were smiling.
Chin to Philtrum Ratio
The height of the lip-to-chin area compared with the height of the philtrum above the lip.
What it is
The philtrum is the groove between the nose and the upper lip. This ratio compares the distance from the lower lip to the chin with the distance from the nose to the upper lip. The classic reference is about 2:1.
How it's measured
The lower lip to chin distance is divided by the nose-base to upper-lip distance, both measured vertically from landmarks.
Definition: the distance from the lower lip to the bottom of the chin, divided by the distance from the base of the nose to the upper lip.
How it's read
A chin region about twice the philtrum reads as balanced. A taller philtrum or a short chin lowers the ratio and a short philtrum raises it, and a shorter philtrum is generally the more feminine look, so the female range sits a little higher.
What affects it
Tilting your head up or down changes the apparent lip-to-chin distance, so keep level. Smiling stretches the philtrum, so use a closed neutral mouth.
See it on a full report
Open the sample report to see every measurement, score and highlight on a real example.