Enter the diamond’s length and width into the calculator to determine its length-to-width ratio (L/W).
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Diamond Length-to-Width Ratio Formula
The following equation is used to calculate a diamond’s length-to-width ratio (L/W).
LWR = L/W
- Where LWR is the diamond length-to-width ratio (a dimensionless value).
- L is the face-up length of the diamond (typically the longest dimension).
- W is the face-up width of the diamond.
To calculate the length-to-width ratio, divide the face-up length of the diamond by the face-up width of the diamond.
What is a Diamond Length-to-Width Ratio?
Definition:
A diamond’s length-to-width ratio (L/W) is a simple proportion used to describe how elongated a diamond’s outline looks when viewed face-up. It’s commonly referenced for fancy shapes (such as oval, pear, marquise, emerald, radiant, and cushion cuts). For round diamonds, the ratio is typically close to 1.00.
The length-to-width ratio is not the same thing as a laboratory “cut grade.” Cut quality depends on many factors (for example: table %, depth %, crown/pavilion angles, and facet alignment), and major labs evaluate cut using comprehensive criteria rather than just the L/W ratio.
For example, the GIA (Gemological Institute of America) introduced its cut grading system for standard round brilliant diamonds in 2005. In the GIA system, cut grade categories are:
Excellent: The highest GIA cut grade for round brilliants; indicates strong overall light performance and well-executed proportions/finish within GIA’s criteria.
Very Good: Minor proportion or finish variations that typically have little visible impact on appearance compared with Excellent.
Good: Noticeable deviations from top proportion ranges; can still appear attractive, but light performance may be reduced compared with higher grades.
Fair: Proportions and/or finish that commonly reduce brightness and fire; appearance may be visibly affected.
Poor: Significant proportion and/or finish issues that generally result in low light performance.
