Carat is the term that refers to the weight of a diamond. Before the twentieth century, diamonds were weighed on balance scales using the carob seed (hence the word carat used today) because they are extremely uniform in weight=1/5 of a gm.
When rough diamonds are cut and polished into finished diamonds, as much as 6o percent of the total carat weight can be lost. The value and price of diamonds rises exponentially with each increase in carat weight due to its rarity.
Diamonds are weighed in metric carats. Five carats is equal to one gram, thus one carat is equal to 0.2 grams. Today, a carat weighs exactly the same in every corner of the world. Carat is divided into 100 points. For example, a 75-point diamond weighs 0.75 carats.