Diamond weight is calculated in carats. One full carat or 1.00 ct weighs 200 milligrams, which is one fifth of a gram. A carat can also be divided into one hundred points. A quarter of a carat diamond can be described as .25 ct , which can also be called  a twenty-five pointer. A one and a half carat diamond is also described as 1.50 ct. Diamond professionals use very accurate and sensitive scales to weigh the diamonds these scales differentiate as close to a thousandth of a carat and round them up to the nearest point.

The word carat originates from the faultlessly even carob seeds that were used in early times to balance scales by merchants. These little carob seeds are so identical and proportioned in shape and weight that even today's refined and complex measuring tools cannot identify more than three one-thousandths of a difference among them.

The reality in diamond shopping is that size is sought after, naturally; but overall quality is a far more important aspect. There is a unique balance in size and quality that makes up the work of a diamond cutter or a gemologist. It is the gemologists job to cut and shape gorgeous diamonds, while giving the customer a diamond with the highest Carat Weight and balance of brilliance for their money.

Most people shopping for diamonds want them as big as they can get within their outlined budget. And the easy way to perceive carat weight is with the logic that the more a stone weighs, the bigger it must be. This is not true because a diamond's cut can cause a lot of the weight to be in places that are not seen at all for example a diamond with a big culet or girdle weighs as much as a diferant diamond that has all that weight in its table. And shape also has a lot to do with how big the diamond appears. Try thinking about how you see a diamond when it's set inside a ring. From the top you only view the diamond's table or top facet. Two diamonds which have the same carat weight can have totaly different measurements. Also diamonds with too high depth percentage have excess weight in places that can never be seen if the diamond is set in a ring. When you are shopping for a diamond in a certain weight range, pay a lot of attention to the average diameters and depth and table percentages of other diamonds in the same range. This will help you determine if you are really paying for optically wasted weight. And on the other side, look outfor diamonds with too much spread, these can often take away the entire brilliance of a diamond.

Lastly, there's a special plus for people who would rather prefer a flat shaped diamond such as ovals, pears, hearts, marquise' and princess, etc. Because when these diamonds are viewed face up, these shapes often look much larger than round diamonds of the same weight.

Only one fifth of all rough diamonds that are mined are fitting for gem quality. Rough diamond is the unrefined material that cutters work with. The cutter must follow the very precise set of formulas to cut each and every stone. A diamond shape such as round or princess doesn't really affect a stone's value. The cutter's expertise is the most determining factor in creating the immeasurable beauty of a diamond. When a certificate is included, the professional appraisal will give you the diamond's exact measurement and weight, as well as the details of all the other factors, cut, clarity and color. For exact dependability, this analysis must always be done in a non affiliated and accredited diamond appraisal laboratory.