A carat is the unit of weight used to measure diamonds and other precious gemstones, also known as the carat size or the diamond carat size. The term carat is derived from the Greek word keration, meaning carob beans. In the Mediterranean, carob beans were used for centuries to measure the weight of various goods. This is because carob seeds were thought to be uniform in size and weight. In contrast, Asian markets used grains of rice to measure their goods and you may still hear some jewelers refer to a single carat diamond as a "four grainer" since one carat was once considered to be equal to the weight of four grains of rice. By the early 1900s, the carat size was standardized against the metric system and adopted internationally: 1 carat (1ct) is equal to .2 grams or .007 ounces. Smaller diamonds can also be measured in carat weight points. One carat is equal to 100 points; therefore a 0.25 carat diamond can also be referred to as a 25 point diamond.
Does Carat Weight Determine Size?
Contrary to popular belief, carat weight is not an accurate reflection of a diamond's size, the carat size. A diamond increases in weight much faster than it increases in diameter. While small round diamonds that have the same carat weight are almost indistinguishable in size, the heavier a diamond gets, the less predictable its size is.
In order to determine a diamond's size, the carat weight of the stone should be weighed in conjunction with the diamond's diameter in millimeters and the diamond's cut grade. The diamond's diameter measured in millimeters reflects the appearance of the diamond as seen from above once the stone is mounted. It is measured across the girdle of the stone, and does not incorporate the height of the pavilion.
Some low carat diamonds with high grade cuts look larger than high carat diamonds with low grade cuts. Diamonds with higher cut grades reflect the maximum amount of light and generate the greatest fire and brilliance. This bright sparkle and intense luminescence can frequently cause the diamond to appear larger than it is, to create the impression of a large diamond carat size. Moreover, diamonds with lower cut grades can have long and deep pavilions that cause light to "leak out", dulling and muting the stone's radiance. These long pavilions may add weight to a diamond, but this weight is covered beneath the setting once the stone is mounted, making the diamond carat size appear much smaller. Viewers of diamonds such as these may be surprised by how small the stones appear in comparison to their carat weight.Carat Weight and Price
Diamond prices rise drastically with increase in carat weight. This is because only one in approximately one million diamonds mined produces a full cut and polished one carat diamond. During the cutting process, a great deal of rough diamond material is lost; up to 40-60 percent of rough diamond is shed. The larger diamond, the rarer the diamond, the more expensive.
What Carat Weight Should I Choose?
Every diamond wearer has different criteria regarding their diamond, popular carat sizes vary greatly. Some value diamond carat size over clarity, others value color over carat weight. At Zoara we believe that the most important things to consider are personal taste, budget, and for a diamond ring, the setting and size of the finger or hand of the wearer.
Personal Taste: Decide which of the Four Cs is the most important to you. Some are sensitive to brilliance and sparkle more than size. Others prefer large vintage-style diamonds which are typically less radiant, but greater in carat size.
Budget: If you are looking for a larger stone but you’re on a budget, you can try to maximize the appearance of the stone by investing in the stone's cut and choosing a brilliant shape. You may instead prefer to invest in a stone of high carat weight but with lower clarity, color and cut grades. Choosing a large diamond carat size over a large carat weight
Setting: Diamonds that are longer in shape such as a marquis, pear, or rectangular emerald, can create the illusion of a larger diamond. Also, if a diamond is mounted into a high-pronged setting such as the tiffany setting or the tall prong setting, it can make a stone look larger. Finally, adding side accent stones of low carat and lower quality can be an affordable way to enlarge the ring and total carat weight.
Finger Size: Small diamonds appear larger on small hands and vice-versa. Large diamonds can look clumsy on small or slender fingers. For a woman with small and thin fingers, you may want to consider a diamond of lower carat weight and a lower carat size.
Total carat weight (ctw) refers to the total weight of all diamonds set in the jewelry item. For example, in order to calculate the TCW of a three stone ring, one would take into consideration the center diamond as well as the two side stones.