In Depth: Carat Weight

If you’re looking at engagement rings, you’ve probably become somewhat familiar with the famous “4Cs” of diamonds: color, cut, clarity, and carat weight. Of the four diamond-grading factors commonly used by the Gemological Institute of America, carat weight is the least subjective and the easiest to understand.

In Depth: Carat Weight

However, it’s not all as straightforward as it might seem. There are a few things you’ll want to consider about carat weight before you buy a diamond engagement ring.

The Basics

What is carat weight in diamonds? The term “carat weight” refers to the physical weight of a diamond. To know how to tell carat weight of diamonds, jewelry professionals use a measurement device called a carat scale.

The weight of diamond carats in grams is 1 carat = 0.2 grams, or 200 milligrams. Five carats are equivalent to one gram. Each carat is subdivided into 100 points, much like a dollar contains 100 pennies. This allows for an incredibly precise measurement to be placed on each stone.

Generally, the heavier the carat weight of the diamond, the larger it is and the rarer and more valuable it becomes. However, other factors, including the three other remaining Cs (cut, color, and clarity), also impact the rarity and value of a diamond.

Carat Weight Vs. Appearance

There is an important difference between a diamond’s carat weight and its visual size appearance. It’s not always the case that the more a diamond weighs, the larger it looks.


Two diamonds of the same carat weight can seem like they are different sizes because of their shape. Elongated shapes such as ovals and emerald-cut diamonds tend to appear larger than round or square shapes, even if their weight is the same.

Whether a diamond of a specific size looks its weight also depends on how well it is cut. If a rough stone is not cut well, it will have too much depth. This means the diamond carries more weight in its height, where it will not add to the visual perception of its size.

Size Categories

Diamonds are priced per carat by size brackets in ranges of 0.0-0.49 carats, 0.50-0.99 carats, 1.00-1.49 carats, 1.50-1.99 carats, 2.0-2.49 carats, and so forth. A diamond just below a breakpoint can look quite similar in appearance to one just above the breakpoint but will cost substantially less. These diamonds are known within the diamond industry as “magic sizes.”

Because of their value and the exacting nature of diamond cutting, most rough diamonds are designed to weigh in above the breakpoint threshold (not below it) once the process is complete and the diamond has been polished. As a result, diamonds just below the breakpoints are much harder to find.