The term “carat” is the standard unit of weight for diamonds and other gemstones. The name originates from the carob seed, which was the original unit of measure for diamond traders. In 1913 the United States implemented the modern metric carat, which is equal to 0.2 grams, and other countries soon followed. Today, a carat means the same thing everywhere in the world.
A carat can be further divided into 100 points, allowing for very precise measurements. This is critical for jewelers as even a very small weight difference can have an impact on the overall diamond value and pricing structure.
Diamond Carat Size ComparisonJust as two people, one who is tall and thin and the other who is short and stout, might weigh the same on the bathroom scale, two diamonds that appear to be different sizes might actually have the same carat weight. That’s because variations in shape and cut make diamonds of similar weights look different. Since carat weight is distributed over the entire diamond, other measurements are needed to describe the overall size:
Crown Area – this is the total surface area of the top of the diamond (measured in mm2). It shows the size of the diamond as it appears face up, similar to how we view a diamond when set in a ring.
Cut Proportions – if two diamonds are the same carat weight and shape, but one carries a larger percentage of its weight in its depth, then the table percentage (flat section at the top of the diamond) and overall crown area will be smaller, giving the impression that the diamond is smaller from the top. The photo (right) shows two 1 ct. round diamonds, but the diamond on the left is cut deeper and therefore has a smaller table percentage across the top.
Shape – diamond shapes such as oval or marquise have elongated lengths, resulting in the appearance of a larger size per carat weight. Sometimes this size difference can be real, however, it can also be just an illusion based on perception.
It is important to explain to your customers how these different factors affect the perception of diamond size. A diamond with a higher carat weight is likely to be more expensive, but may not look that much larger than a smaller carat weight diamond once set in jewelry. Help your customer find a diamond that gives the largest perception of size for the jewelry setting they like, while staying within their budget.
by Shoshi Grossman