# Lower Third Proportion

Harmony · Front view · Jaw · https://www.faceiqlabs.com/support/harmony/lower-third-proportion

The upper portion of the lower third, from nose bottom to mouth seam, relative to the whole lower third.

## What is measured

Calculation: Nose-bottom-to-mouth-seam height ÷ nose-bottom-to-chin height × 100

## Why it matters

This explains where the mouth sits within the lower face. It includes the upper lip and the space above it; it is not simply chin height as a percentage of the lower third.

- Lower: the mouth seam sits closer to the nose bottom.
- Higher: the mouth seam sits farther down the lower third.

## Where the idea comes from

Evidence: Classical proportion. The classical lower-face subdivision compares the portion above the mouth with the portion below. FaceIQ makes that relationship explicit using its nose-bottom, mouth-seam and chin landmarks.

## A worked example

A nose-to-seam span of 21 units in a 64-unit lower third gives 32.8%.

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

## How to read your result

Do not substitute the upper-lip border for the mouth seam. A parted mouth changes the reference.

## 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/lower-third-proportion · FaceIQ Labs overview for AI assistants: https://www.faceiqlabs.com/llms.txt