The carat is the standard unit of measure used when weighing precious gemstones. Five carats equals one gram. So, one carat is equal to 1/5 of a gram (or .2 grams). There are 100 "points" to a carat. So, a carat weight of .50 is the same as a carat weight of 1/2 carat. A carat weight of .75 means 3/4 of a carat, and so on.