Facial index: the ratio of face height to face width
Quick facts
- Definition
- Ratio between the morphological height and the bizygomatic width of the face, usually expressed as a percentage.
- Formula
- Height (nasion to gnathion) divided by width (between the most lateral points of the zygoma), times 100.
- Classification
- Wider or longer faces, according to ranges defined in each reference table.
- Limit
- It is a proportion measure with no absolute normal value, and it varies with age and ethnicity.
The facial index is an anthropometric measurement that relates the height of the face to its width. It describes whether the face is wider, longer or intermediate. It is one of the classic indices of facial anthropometry.
How is it calculated?
Facial index = (morphological face height ÷ bizygomatic width) × 100.
The height runs from the nasion to the gnathion, the lowest point of the chin (near the pogonion). The width is measured between the most lateral points of the zygomatic arches.
Hypothetical example: a height of 120 mm and a width of 135 mm give 120 ÷ 135 × 100, about 89. A longer face would give a higher number; a wider face, a lower one. The classification ranges depend on the table adopted, so cite the reference you use.
How does the index help, and where does it fall short?
It helps describe the face objectively and relate to the face shape, such as oval, round or long. It falls short because it is a single ratio: it says nothing about profile, symmetry, projection or soft tissue. It also varies with age, population and head position during measurement.
| Information | Does the index show it? |
|---|---|
| Wide or long face | Yes |
| Projection of the cheekbone or chin | No |
| Symmetry | No |
| Proportion of the thirds | No |
Frequently asked questions
How is the facial index calculated?
Divide the face height (nasion to gnathion) by the width between the zygomatic arches and multiply by 100. The result shows whether the face is wider or longer.