---
title: "Symmetry (light performance): meaning in gemology"
description: "In our light-performance scores, symmetry measures how evenly the pavilion facets of each angle family are cut. It reads 100 when every facet in a family…"
url: https://digitalgemology.com/learn/glossary/symmetry-light-performance
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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[Glossary](https://digitalgemology.com/learn/glossary) · Light performance

# Symmetry (light performance)

Also called pavilion symmetry score

In our light-performance scores, symmetry measures how evenly the pavilion facets of each angle family are cut. It reads 100 when every facet in a family has the same angle and distance from the center.

## In more detail

It is not the symmetry grade on a grading report. A report grade judges how exactly a real stone's facets are shaped, placed and aligned. Our score reads the cut's geometry only: a multi-angle pavilion counts as design, not as asymmetry. The Hearts & Arrows Scope gives a third, separate symmetry figure.

## How we measure it

We group the pavilion facets into families. A new family starts where consecutive angles differ by more than 0.45°. For each family, we take the standard deviation of its angles, in degrees. We add 57.3 × the relative standard deviation of the facets' distances from the center. σ is the size-weighted mean of that sum, and Y = max(0, 100 − 6σ). It is the same in every gemstone.

## Related terms

- [Symmetry](https://digitalgemology.com/learn/glossary/symmetry): Symmetry is the report grade, from Excellent to Poor, for the exactness of a stone's outline. It also covers the shape, placement and alignment of the facets.
- [Hearts and arrows symmetry](https://digitalgemology.com/learn/glossary/hearts-and-arrows-symmetry): Hearts and arrows symmetry is the share of a hearts and arrows pattern where all sixteen halves match. Our Hearts & Arrows Scope gives it as a whole percent for each view.
- [Overall score](https://digitalgemology.com/learn/glossary/overall-score): The overall score is one figure out of 100 that combines our light-performance scores for one cut in one gemstone. The Cut Performance Wheel calls it Global.
- [Cut Performance Wheel](https://digitalgemology.com/learn/glossary/cut-performance-wheel): The Cut Performance Wheel is a free Digital Gemology tool. It draws eight light-performance scores of one cut, in one gemstone, on a wheel.
- [Mirror-image symmetry (design)](https://digitalgemology.com/learn/glossary/mirror-image-symmetry): Mirror-image symmetry in a faceting design is the number of identical mirrored sections around the stone. An 8-fold mirror-image design repeats the same pair of mirrored halves eight times.

## Learn more

- [Cut Performance Wheel and cut-page scores](https://digitalgemology.com/about/how-we-measure/performance-wheel)
- [Digital Gemology Cut Performance Index](https://digitalgemology.com/learn/cut-performance-index)

[All 328 terms](https://digitalgemology.com/learn/glossary)