What Is a Diamond Carat?

To put it simply, diamond carat weight measures how much a diamond weighs. A misperception is that a larger carat weight is always better than a smaller carat weigh. A metric “carat” is defined as 200 milligrams. Each carat is subdivided into 100 ‘points.’ This allows very precise measurements to the hundredth decimal place. A jeweler may describe the weight of a diamond below one carat by its ‘points’ alone. For example a 1.08 carat stone would be ‘one point oh eight carats.’

Diamond Carat Price
Diamonds with higher carat weights are cut from larger rough crystals that are harder to source than small crystals. So, the relationship between carat weight and price depends on the rarity or availability of a rough crystal. Carat price is also a function of finding rough crystals with desirable color, and internal and external characteristics that will positively influence clarity when the diamond is cut.

HOW DID THE CARAT SYSTEM START?
In order to understand what a diamond carat measures, it would help to know the origins of the modern carat system. Carat weight started with the carob seed, when early gem traders used the small, uniform seeds as counterweights in their balance scales. Today, the carat is the same milligram weight in every corner of the world.

WHAT ARE “MAGIC SIZES”?
Some weights are considered “magic sizes” – half carat, three-quarter carat, and carat. Visually, there’s little difference between a 0.99 carat diamond and one that weighs a full carat. But the price differences between the two can be significant.