Carat weight is the weight of the diamond measured in carats. One carat is divided into 100 "points," so that a diamond of 75 points weighs 0.75 carats. Carat weight is the most obvious factor in determining the value of a diamond. But two diamonds of equal carat weights may have very different prices, depending on their quality.

Since diamonds are measured by carat weight, and not size, two diamonds of the same weight could have different sizes. Why? If a diamond is cut too shallow (or flat) it will have a larger diameter, but shallow depth and appear larger. Likewise, if a diamond is cut too deep (or pointed) it will have a smaller diameter and deep depth and appear smaller. This is why cut is so important. You want to make sure the diamond is cut to proper proportions. Not only does it make a large difference in the diamond's ability to reflect light, but a poorly cut diamond will not be proportionate in size to a diamond cut to proper specifications. For example, let's say you're interested in a 1.00ct diamond solitaire with a table of only 49%, the diamond will be cut way too steep and will look like a 0.80ct diamond instead.