Contrary to popular understanding, a diamonds carat measurement refers to its weight as opposed to its physical size. Carat weight is just one of the 4C’s that are considered when grading the quality of a diamond, the others being its clarity, colour and cut. Different diamond shapes and cuts have different carat weight. At Harper Tait we select a stone for its overall quality prioritising beauty and fire over its physical size.
Although there are a number of other contributing factors that affect the appearance of a diamond, such as cut and shape, you can generally expect the stone to appear larger as the carat weight increases.
Download our carat size chart here as an indication of diamond carat size.
A metric carat is equal to 0.2 grams or 0.007 of an ounce. One carat is divided into 100 points. Diamonds are weighed to one-thousandth of a carat and then rounded up to the nearest point, expressed as carats and decimals (e.g. 1.05 carats) or points (e.g. 75 points). A fraction of a carat can affect the price of a diamond by hundreds or thousands of pounds, however, it should be remembered that this is a measure of rarity as opposed to just quantity. Large diamonds are rarer than small diamonds; that is why they are more valuable, not just because they are bigger. That is why a two-carat diamond will be worth more than twice as much as a one-carat stone.
There are also ‘magic numbers’ where the price shoots up dramatically. A one-carat diamond will cost significantly more than a 99 point one, even though they are almost indistinguishable regarding size and appearance. 50 points (half a carat) and 75 points (three-quarters of a carat) are similar symbolic thresholds.
While the four C’s are the universal measures of a diamond’s objective value, we encourage our clients to look beyond these and to choose a diamond that is right for them. However, understanding this grading system is the only way to know how the value of a diamond is arrived at, and as such is an essential part of the buying process.
