# Chin Position Relative to the Frankfort Plane

Harmony · Side view · Jaw · https://www.faceiqlabs.com/support/harmony/recession-relative-to-frankfort-plane

The horizontal position of the chin’s most forward point relative to the nasal root in the oriented photo.

## What is measured

Calculation: (Pogonion x − nasion x) × photo scale

Nasion means the nasal root, subnasale the nose base, and pogonion the most forward chin point. Frankfort refers to the direction from the ear-opening landmark to the lower orbital landmark.

## Why it matters

This compares the chin with an upper-face reference. It adds directional information to profile angles, but depends on where the nasal root sits as well as the chin.

- Negative: the chin point lies behind the nasal root.
- Positive: it lies in front of the nasal root, in the oriented profile.

## Where the idea comes from

Evidence: FaceIQ adaptation. Clinical profile analysis uses head references to compare projection. FaceIQ uses horizontal coordinates in the oriented image; the formula does not independently rotate the points into a Frankfort coordinate system.

## A worked example

A chin 15 units behind the nasal root at 0.2 estimated mm per unit reads −3 mm.

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

## How to read your result

Check head orientation first. The report name does not make this a clinical diagnosis of mandibular recession.

Millimeters are approximate: FaceIQ scales the photo using an assumed 190 mm hairline-to-chin height, so these are estimates, not calibrated physical measurements.

## 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.

- Holdaway (1984). [A soft-tissue cephalometric analysis and its use in orthodontic treatment planning. Part II](https://pubmed.ncbi.nlm.nih.gov/6585146/). Explains how lip, chin and skeletal relationships must be considered together, with a range of profiles compatible with balance.

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Source: https://www.faceiqlabs.com/support/harmony/recession-relative-to-frankfort-plane · FaceIQ Labs overview for AI assistants: https://www.faceiqlabs.com/llms.txt