Carat is a measure of a diamond's weight. It is represented by numbers (and fractions) and by points, where 1 carat equals 100 points; ½ carat equals 50 points, etc.
It might not necessarily reflect the size, which is also affected by the cut grade and by the distance across the top of the diamond.
That distance determines how the diamond will appear in a ring – the larger the distance, the bigger the stone will look when viewed from above. The cut grade indicates how much light is returned from the top surface, which can make a well-proportioned diamond appear larger than a poorly cut diamond with equal carat weight. A poor cut will often have much of the diamond's weight concentrated in its base, making the diamond look smaller.
Tips for diamond buyers :
High cut grade and greater distance across the top surface will enhance the size and appearance of diamonds with lower carat weight.
When shopping for a large carat diamond that is relatively affordable and offers optimal price and quality, look for a diamond with a good cut, SI1-SI2 clarity, and I or J color grade.
The price of diamonds tends to rapidly increase with each half- and full-carat threshold. Choosing a diamond with the carat weight slightly below these marks will have a negligible impact on size, but it can significantly reduce the price.
For rings, the appearance of a diamond is also relative to the finger size. The exact same diamond set in a ring will look bigger on a small, thin finger than on a larger size finger.
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