The weight of a diamond is discussed in terms of carat weight. A one carat round diamond ring, or one of any other cut, would feature a diamond which weighs exactly one carat, or 200 milligrams. Carat vs Carrot “Carrot” is a vegetable, and also a frequent misspelling of “carat”. In case you come across advertisements or pop up ads on the internet peddling a “one carrot diamond ring” available for a cheap price, you should know this says nothing about how much the stone weighs, or even whether it is authentic. Have you ever wondered why carat is expressed as a measure of a diamond’s weight? This particular term comes from an ancient period where every gemstone was weighed against a carob bean. With no weighing scale to get measurements, this was all they had for measuring the weight of something as valuable as a diamond. Carat Weight and Size People also confuse carat weight and size; they are not one and the same, although people commonly use the terms interchangeably. Two diamonds of equal carat weights can differ in terms of dimensions, depending on how diamond cutters have proportioned it. By proportioning the gemstones for maximum yield of the carat, many diamonds are cut more thickly and deeply at the portion called the girdle.