# Chin-to-Philtrum Ratio

Harmony · Front view · Mouth · https://www.faceiqlabs.com/support/harmony/chin-to-philtrum-ratio

The span below the lower lip compared with the span between the nose base and upper lip.

## What is measured

Calculation: Lower-lip-to-chin height ÷ nasal-base-to-Cupid’s-bow height

## Why it matters

This compares two vertical spaces around the lips. A tall chin region and a short philtrum can both increase the number; neither follows from the ratio alone.

- Lower: less chin-region height relative to philtrum height.
- Higher: more chin-region height relative to philtrum height.

## Where the idea comes from

Evidence: FaceIQ adaptation. Subdividing the lower face develops the classical proportion approach. FaceIQ uses the lower-lip edge and Cupid’s bow as the inner endpoints, which should be checked before comparing with another measurement method.

## A worked example

A 32-unit lower-lip-to-chin span and 14-unit philtrum give 2.29. A 16-unit philtrum lowers the ratio to 2.0.

Example values explain the calculation. They are not a target range.

## How to read your result

This uses chin height, not forward chin projection. Lip position affects both nearby endpoints.

## Research & further reading

These sources explain the history or related evidence. FaceIQ’s score weights and reference ranges are model settings; the papers do not collectively validate the scoring system.

- Farkas et al. (1985). [Vertical and horizontal proportions of the face: revision of neoclassical canons](https://pubmed.ncbi.nlm.nih.gov/3883374/). Tested nine traditional proportion rules against measured faces. Useful history for facial thirds and width comparisons; classical rules are not universal targets.

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Source: https://www.faceiqlabs.com/support/harmony/chin-to-philtrum-ratio · FaceIQ Labs overview for AI assistants: https://www.faceiqlabs.com/llms.txt