When it comes to the appearance and light performance of a diamond, depth and table size are particularly influential. Here’s a breakdown of exactly how these factors affect the overall cut quality of a diamond, as well as some tips on what to look for when it comes to understanding diamond depth and table.
What’s Diamond Depth?
In short, the depth of a diamond is the distance from the culet to the table and is given in millimeters. However, there are actually two numbers associated with depth. The first is the actual distance in millimeters, but that’s often accompanied by a measurement of depth percentage, which is a proportion of how the depth of a diamond relates to its width. A high depth percentage indicates a diamond that is too tall, while a low percentage indicates that it’s too wide.
The depth of a diamond is particularly important when it comes to how light is reflected, which means that the depth plays a large role in how a diamond looks. Better looking diamonds, with optimal sparkle and light return, often have very specific depths and depth percentages.
What’s Wrong With Extreme Depth Proportions?
In diamonds, the depth percentage correlates to brilliance and value. If the pavilion facets are cut properly, light rays will bounce ideally within the diamond and create the most attractive appearance possible to the viewer.
However, if they’re cut poorly and end up not being in proportion to the rest of the diamond, then you can end up with dark nailheads and ugly fish-eye effects. Too much or too little depth can both lead to unintended and unattractive appearances.
However, there isn’t a single size that fits every diamond. Perfect depth percentage varies from diamond to diamond, with the shape determining what would look best. A perfect depth percentage for one diamond might be quite unappealing in another.
For example, consider a princess cut, where you’d want around 63% to 69% for the best appearance. If you then looked at rough cut diamonds with those same depth proportions, you’d be looking at diamonds that are not only not excellent, but not even good.
What’s the Table of a Diamond?
The table of a diamond is quite simple the large flat facet of a diamond that points straight up. Aside from being the most obvious face of a diamond, it also plays a critical role when it comes to just how brilliant a diamond is.
Table percentage is used to show how the size of the table compares to the average girdle diameter of the rest of the diamond. In other words, if you were looking straight down at a diamond that had a 60% table percentage, you would see that the table was 60% as wide as the entire diamond.
For round cut diamonds, the value is pretty easy to compute. All you have to do is divide the diameter of the table by the average girdle diameter, with all measurements being in millimeters. Sellers often include such basic measurements with every diamond, so if you really wanted to, you could compute the table percentage on your own.
For other shapes, it can be tougher, but is still accomplished by dividing the diameter of the table by the widest part of the entire stone.
Why Does Table Size Matter?
As the most exposed and obvious part of a diamond, the table plays an integral role in refracting light rays and redirecting light pack into the eye of the viewer.
Some people think that a bigger table percentage is ideal, but that couldn’t be further from the truth. There are many different factors interacting with one another, so a smaller table percentage could easily lead to a far more brilliant appearance.
One of the main effects of the table size is how it affects fire dispersion. This is mainly because fire is seen at the bezel facets. A bigger table means smaller bezel facets and less fire dispersion. To contrast, a smaller table means bigger bezel facets and thus more fire dispersion.
However, you don’t necessarily want to have a tiny table either. Just like the size of the bezel facets increases fire dispersion, so too does the size of the table correspond to increased brilliance. Therefore, it’s necessary to strike a delicate balance between the two if you want to get the best of both worlds.
Are There Ideal Depth and Table Percentages?
With diamonds, there are ideal ranges of values for both depth and table, but there is a major caveat: the range depends on exactly what sort of shape your diamond is.
- For example, a round diamond wants to have a table percentage of 54% to 57%, as well as a depth percentage of 61% to 62.5%. As you will see shortly, these are extremely narrow ranges in comparison to the competition.
- An oval diamond wants anywhere from 52% to 60% for the table percentage, then 60% to 68% for the depth percentage.
- A princess diamond wants 63% to 69% for table percentage and 69% to 76% for depth percentage.
- A cushion diamond wants 58% to 63% for table percentage and 58% to 66% for depth percentage.
How Should One Use Depth and Table Percentages?
The short and simple version is that depth and table percentages can help you quickly identify which diamonds are worth your time and which are not. However, it’s important to note that the above values are largely for listing absolute ideal conditions, so you can still find diamonds that are just outside those ranges and still quite beautiful, especially if your budget might not allow for the best of the best.
In many cases, a diamond may appear brilliant to the eye, but it’s difficult for the average consumer to tell just how brilliant. However, over a lifetime with that diamond, they may come to appreciate the subtleties or lack thereof. Therefore, it’s important to make that critical purchasing decision with as much information as possible. Just because you don’t notice the flaws now doesn’t mean that will always be true.
When it comes to understanding diamond depth and other precise calculations, you may also need more than a simple chart of acceptable ranges. More detailed measurements like ASET imagery may be needed to determine just how good a diamond is.