What does carat size mean?
You may have noticed that when we talk about the stone size, we typically refer to the millimeter size instead of the carat size. We do this because carat size is referring to the weight of the gemstone, not the dimensions of the stone. So it makes sense to us to refer to the part that you can see. When you look down at your hand with a solitaire engagement ring on, what you see is the dimensions of the stone, not the weight of it. And a round 1ct stone can be larger or smaller in its diameter depending on how deep or shallow the cut is. Because of that, you can have two stones that weigh the same but will look differently on your hand.
Additionally, different types of stones have different weights to them, and since we commonly work with moissanite and sapphires as well as diamonds, using the dimensions of the stone is more relevant as to what will fit in a particular setting. The chart below compares the typical carat weight of the stone sizes to their millimeter size. You can print out a .pdf of this chart to see the actual size of these different stone sizes, and how they might look on your hand (be sure to print at 100%).
Something else to consider when choosing a stone size is the proportions. In the illustration above, the rings are pictured in a US ring size 7 and have a 1.5x1.5mm band. But the dimensions of the different components of a ring will affect how big or small a stone will appear, as you can see below in the illustration of a round 5mm stone size.
