Carat weight is a measurement used to describe the size of gemstones, particularly diamonds. One carat is equivalent to 200 milligrams, or 0.2 grams. The weight of a gemstone can influence its value, with larger stones generally being more valuable due to their rarity. When purchasing a gemstone, it's important to consider carat weight alongside other factors like cut, color, and clarity. These elements together determine the overall quality and price of the stone. For example, two diamonds of the same carat weight can have very different values based on their cut, color, and clarity.