Diamond size and carat weight are often used interchangeably, but they actually refer to different characteristics. Let’s find out what the difference is between size and carat, and see if either of them is more important when choosing a diamond.
How Diamond Carat Weight Is Measured
The carat of a diamond is simply a measure of its weight. One carat (1 ct) is equal to 200 milligrams or 0.2 grams.
Dividing the price of a stone by its carats gives you its price per carat, which is a popular measure used to compare different diamonds to see which is relatively more expensive.
How Diamond Size Is Defined
Broadly speaking, diamond size refers to the height and width of a particular stone, as well as the measurements of some of its key parts.
The dimensions customers are usually most interested in are the size of the stone’s top and the key proportions that determine the quality of the diamond’s cut.
The reason the size of a diamond’s top is so important is simple: This part is the most visible when the stone is set in a piece of jewelry.
On the other hand, having more depth in a diamond won’t do much for how big it looks in a setting as that additional size will be hidden in the mounting.
The overall proportions of a diamond’s cut are also important because they determine how the stone will reflect light and how much brilliance the diamond will exhibit as a result.
Why Carat Weight Is Not the Same as Size
As you can see from the above definitions of carat and size, they are not exactly synonyms. Carat simply refers to how much a diamonds weighs, whereas size is about its dimensions.
Hence, two stones of the same carat can have different dimensions and thus be of different sizes.
Conversely, you can have stones with either the same diameter or the same depth, for example, and these diamonds can still have different carat weights.
What Affects Diamond Size
While it is true that carat weight puts a certain limit on a diamond’s dimensions, the factor that affects them the most is the stone’s cut. Some diamond shapes require the stone to be cut shallow, while other cuts are deeper.
For example, emerald-cut diamonds are rectangular and shallow by design, whereas round cuts and princess cuts have more depth.
Stones of the same cut and carat can also have different sizes depending on how the cutter decided to shape their proportions.
For example, two 1-carat round diamonds can have different widths or heights. And even if these two stones weigh the same, the deeper one will appear smaller when set in a ring, while the shallower diamond will seem larger.
How Diamond Size Affects Carat Weight
By varying the size of certain parts of a diamond, the jeweler cutting it can end up with a heavier or lighter stone.
For example, if there are two round diamonds with the same diameter, and one of them is cut deeper and with a thicker girdle, that stone will be heavier.
The deeper diamond could be more expensive just because it weighs more, although from the top, it won’t look bigger compared to the shallower stone.
Carat Weight, Size, and Diamond Prices
Carat weight is an important price determinant, and since bigger diamonds are rarer, their price per carat is higher. So it is understandable that a jeweler will try to cut a diamond in dimensions that increase its carat.
However, diamond cutters don’t have unlimited leeway when it comes to deciding on a stone’s size.
This is because tweaking diamond dimensions to increase carat after a certain point can result in a disproportional cut that gets a poor quality rating.
And since cut quality is also a major price factor, cutters try to balance carat weight and proportions by finding the right size that will yield the best price for the stone.
Should You Focus More on a Diamond’s Size or on its Carat Weight?
When choosing a diamond, a lot of people look for the biggest stone for the best price they can get.
Although it is understandable that you may want your diamond to be as visible as possible, you shouldn’t forget that it also needs to be the right size – i.e., the stone should have the right proportions.
The more proportional the cut of a stone, the more brilliance and sparkle it will have. Poorly cut stones let most of the light entering them leak out and end up looking dull and drab.
For example, a round diamond that is cut very shallow may look really big when set in a ring, but since the stone lacks depth and has a poor cut, the diamond will not have much brilliance.
So, when looking at the size of a diamond that you are about to buy, you should always check its cut grade.
Look for diamonds that will have a reasonably sized visible area when set in a mounting while also having a high-grade cut. Big but poorly cut stones are just not worth it.