Diamond Carat Weight

The weight or size of a diamond is measured in carats. Carats are a measure of weight, not size. A carat weighs 0.2 grams. There are 100 points (200 milligrams) per carat. Carat weight is measured to a highly precise accuracy of 1/100,000 carats. This weight will be specified on a Diamond Report to two decimal points.

Diamond pricing is determined based on carat weight, and broken down in half-carat increments. For that reason, assuming elements like cut and quality are equal, the price of a diamond rises as the carat weight increases. The rarity of larger, top notch diamonds has resulted in substantial cost escalations between sizes. For instance, a one-carat diamond can command four to 6 times more than a half-carat diamond.

While carat measurement shows the weight of a diamond, the stone's length and width measurements indicate the actual physical size, or how big the diamond will appear when seen from above. Diamonds of the same carat weight can differ in size. For instance, a one-carat round diamond might be 5.9 mm in diameter, while another one-carat round diamond could be 6.5 mm in diameter.

The shape of a diamond also influences how the stone appears. Diamonds cut at lower depths will have bigger lengths and widths. Shapes like oval or marquise will have lengthened lengths, resulting in the impression of a larger size per carat weight.

In addition, when selecting a carat weight, make certain to consider the ring size of the wearer.  A one-carat diamond will appear substantially larger on a Size 5 finger than it would on a Size 9 finger.