• The golden rule of success - an alloy of money.
    Mykhaylovskyy Logo


What is a carat?

Diamonds are sold by weight in carats (ct). Do not confuse this acronym of unit of weight of diamonds with abbreviation (kt), adopted in the U.S. to indicate the purity of gold. Since 1913, most countries have agreed to consider carat weight of 200 mg, or 1/5 of a gram.

Until 1913 carat’s weight varied depending on the country of origin - Indian carat differed in weight from the English; and French carat - from Indian, as well as English. It is important to know if you have, or you are going to get very old jewelry; old carat weighed more new metric carats, which emerged after 1913. Therefore, the old three carat stone weighs more than new standard three carats. Today the term "carat" means metric carat, i.e. a carat with 200 mg weight. One gram has 5 carats.

When jewelers talk about the weight of diamonds, then often they call it in points, especially if the weight of the stone is less than one carat. One carat has100 points, so if a jeweler says that the stone weighs 75 points, it means that it weighs 75/100, or ¾ carat. A stone having 25 points weights ¼ carat, and 10 points - 1/10 ct.

Carat is a unit of weight, not size. We would like to emphasize this statement, as many people think that a one-carat stone has a specific size, and that, for example, a one-carat diamond and a one-carat emerald should look the same in size or external parameters; but it is not true.

If you compare one carat diamond and one carat emerald and ruby, you can easily see that. First, emerald is easier than diamond and diamond is easier than ruby. This means that a one-carat emerald will look larger than a one-carat diamond, and ruby will look smaller than diamond. Emerald, having a lower density, has a larger volume per one carat and ruby being heavier, has a smaller volume per one carat.

However, the same amount of material with the same density must have approximately the same weight, so in the case of diamond carat weight reflects a certain size. This size is based on a cut diamond with ideal proportions. Therefore, properly cut diamonds, based on their weight, should be of approximately the same dimensions as shown in the table. But at the same time, remember that these measures can not be applied to other gems.

Weight ratio of the diamond to its diameter:
Weight 0.03 ct = 2.0 mm diameter;
Weight 0.10 ct = 3.0 mm diameter;
Weight 0.30 ct = 4.3 mm diameter;
Weight 1.00 ct = 6.5 mm diameter;
Weight 1.50 ct = 7.5 mm diameter;
Weight 2.00 ct = 8.2 mm diameter;
Weight 3.00 ct = 9.4 mm diameter.