What does ‘carat’ mean? Where did the term originate?

Carat, abbreviated in English as "ct", originated in Greek - Kerátion. The word was adapted from “Carob”, the name for long horned beans. In the early days, gem traders used small bean seeds of the same weight as weights for the scale, so “carat” became the representative word for the weight of the diamond. Many people misunderstand the term “carat” as referring to a diamond’s size, but in fact refers to its weight. Today, carat is the world's most common gem weight unit.

1 carat equals 200 milligrams, or 0.2 grams. 1 carat is divided into 100 points, so 0.50 carat is 50 points. Note that even a minor variation in carat weight would mean a considerable difference in cost, so accurate diamond weight is important. In general, weight is often measured into one of thousands of carats and rounded to 0.01 carats (e.g. 1.01cts).

 

Carat and price

The carat of a diamond directly affects its price, but not in a simple positive ratio. Because high-quality large carat diamonds are extremely rare, the price of diamonds of the same grade in terms of color, clarity, and cut multiplies exponentially with an increase in carat weight. A one-carat diamond is far more expensive than two 0.50cts diamonds of the same quality. The price of a diamond will jump at a specific weight (0.30cts, 0.50cts, 0.70cts, 1.00cts, 1.50cts, 2.00cts ...). Therefore, if their budgets are a little tight, customers may consider buying a diamond that is slightly lower than a specific weight, for example 0.60cts, 0.90cts and so on, so that the visual size of the diamond can be close to the weight of the diamond selected in the heart, while maintaining a certain quality in the other three indicators of color, clarity and cut.

 

The size of a diamond is usually determined by measuring the diameter face-up as this would be the appearance once the diamond is mounted. Please use below tool for comparison of general diamond sizes of different carats.

 

 

 

The following diagram shows general diamond sizes with full cut from range of 0.25 to 3.0 carats.

  

 

However, the size of the same weight of diamonds may be slightly different to the average, due primarily to the cut. For example, a standard one-carat diamond is 6.4mm in diameter; but if the diamond is cut into a thicker shape, the top view will give the impression that the diamond is of a smaller size than the original diameter of 6.4mm. Therefore, in order to accurately calculate the size of the diamond, we recommend considering both the carat and the cut grade at the same time.