The term "carat" refers to the size or weight of a diamond. It's synonym, "karat" refers to the quality of gold. These two words are completely different words and are often confused when talking about jewelry. Carat weight was standardized in the early twentieth century. If you had purchased a 'one-carat' diamond in 1895, it might have weighed anywhere from 0.95 to 1.07 metric carats, depending on where you bought it. But between 1908 and 1930, the standard metric carat was adopted throughout most of Europe and in Japan, Mexico, South Africa, Thailand, the USA, and the USSR. The more carats that are in a diamond, the more valuable it is because larger stones are more rare. The rarity of a diamond is greatly affected by its size. The rarity of a 1.00 carat diamond is much greater than twice that of a .50 carat. Although it only weighs twice as much, the 1.00 carat is statistically much more difficult (rare) to mine than the .50 carat. That is also why a 2-carat diamond might cost 4 times as much as a 1-carat diamond of similar quality. Also, using a rare metal in your wedding ring, such as a platinum engagement ring, makes it more valuable and unique.

How to Measure a Diamond

When you tell people one diamond weighs more than another, they usually understand what you mean-but few consumers realize how precisely diamonds are weighed. Like most gems, diamonds are weighed in metric carats; one carat equals 0.2 gram-a little more than 0.007 (seven thousandths) ounce. In other words, it takes almost 142 carats to equal 1 ounce. But even this is not precise enough for something so precious. Even with relatively inexpensive diamonds, fractions of a carat can represent hundreds of dollars (thousands, with top-quality stones). For this reason, in the diamond industry, weight is measured to a thousandth of a carat and rounded to the nearest hundredth (or point). Some people refer to "points" as a measurement of weight as well. 1 carat = 100 points, so 1/2 carat = 50 points, and 1/4 carat = 25 points. Points can allow for a more precise weight when a fraction of a carat is involved. Below is a carat chart to give you an example of the different sizes of diamonds.