Carats refers to the weight of the diamond. However, carat weight does not accurately convey size. Sometimes a diamond may appear larger when viewed from the top compared to a diamond of the same carat weight.
To accommodate the stretch, the larger looking diamond was most likely cut too shallow and will not reflect light properly. This is where having an excellent cut pays off because it ensures that the weight is distributed appropriately.
Diamonds are more expensive per carat if the weight is a whole carat or half carat value. For this reason, we advise consumers to avoid getting a 1.0 carat diamond if they are trying to stretch their budget.
A diamond that is slightly below or half carat, such as a 0.98 carat diamond or 1.46 carat diamond is a better value and a wise choice.
A carat is exactly 0.20 grams, or 200 milligrams and 100 points per carat.
Not all the diamonds have the same price for the same weigh, because every individual diamond has a different cut, color and clarity, you will never find two identical diamonds.
Every diamond is unique.
Even though the price of a diamond increases exponentially with the carat weight, the actual size does not. The table below illustrates the typical size relationship between diamonds of increasing carat weights.
Note that when carat weight triples (from 1 to 3 carats), perceived size (represented in the images below) roughly triples as well, however the diameter increases only 45% (from 6.50 to 9.40), and crown area (the surface area visible when the diamond is set) slightly more than doubles.
Crown (mm2 )
This is important to keep in mind when reviewing diamonds of any shape; a given increase in diameter will yield a larger increase in surface (crown) area and overall perceived size.
While the third diamond above has a roughly 50% greater diameter than the first, it certainly appears more than 50% larger.