Diamond Carat

The carat is a unit of weight, not size. One carat (ct) weights 0.2g. A carat is divided into units called points. 100 points equals 1 carat (0.5ct or 50 points describes a half carat). If a diamond is ideally round brilliant cut it is possible to gauge weight by the diameter. Conversely if you know the diameter and weight it is possible to determine if it is ideally cut. All things being equal sapphires and Rubies are heavier than diamond whilst Emerald is lighter. Therefore, a 1ct diamond is larger than a 1ct Ruby and smaller than a 1ct Emerald.