The princess cut is quite popular, partly because its square profile makes the visible surface of the diamond bigger, but also because it has a lot of brilliance. Before you buy a princess-cut diamond, it is important that you know how this type of cut is measured and what its measurements mean.
Why Measure a Princess-Cut Diamond?
Princess-cut stones are usually measured to determine how close their dimensions are to those of a well-proportioned diamond.
Although there are no strict standards for the proportions of the ideal princess cut, there are some rough guidelines.
Knowing the measurements of a princess-cut diamond allows you to calculate some important ratios and compare them with the benchmarks for this cut.
Let’s first see what dimensions you need to measure.
The Most Important Measurements of Princess Cut
The most important measurements for a princess-cut diamond are the thickness of its girdle, its length and width, the width of its table, and the stone’s depth.
Let’s see how each of these characteristics is defined:
The girdle is the outer edge of a diamond – i.e., the stone’s widest part – and is evaluated on whether it is too thin or too thick.
The thickness of a princess-cut diamond’s girdle is measured vertically, so you will simply need to determine its height.
Length and Width
The length and width of a princess-cut stone are important because they indicate whether the diamond has a square profile or a more oblong one.
These dimensions are measured along the stone’s girdle.
The table of a princess cut is the rectangular flat facet on the top of the stone. (The width of the table is less than the width of the entire diamond.)
To determine the table’s width, you should measure one of the sides parallel to the width of the diamond.
The depth of a princess-cut diamond is the distance from its table to the bottom of the stone.
There are a variety of ways to measure a diamond’s depth – one of the most precise options is to take this measurement with a leveridge gauge (a tool that jewelers use to measure gemstones).
How to Use the Measurements of a Princess-Cut Diamond
The measurements described above can be used to evaluate the quality of a princess cut.
Here are the most often used quality characteristics for this type of cut, along with explanations on how to calculate and interpret them:
- Depth percentage: To calculate this characteristic, divide the stone’s depth by its width. A value between 60% and 80% is considered good.
- Table percentage: This is calculated by dividing the width of the table by the width of the stone. Well-cut princess diamonds have a table percentage in the 56-80% range.
- Length-to-width ratio: Simply divide the stone’s length by its width – both measured along the girdle.Princess cuts for which this ratio is close to 1 are preferred (i.e., as close to a square shape as possible). Values in the range 1-1.1 are in most demand.
- Girdle thickness: This characteristic is usually assigned a grade in the diamond’s grading report. Girdles rated from Very Thin to Thick are acceptable, while those graded Extremely Thin or Extremely Thick are less desirable.