Carat Weight in Grading Diamonds

The fourth and final C in evaluating a diamond for purchase is the carat weight. The term carat is a reference to biblical times when diamonds were compared against a carob bean because carob beans tend to have a uniform size and weight. One carob bean became the equivalent of one carat. The carat is still the primary unit of diamond weight used today. However, a carat is further broken down into 100 sub units called points. One point equals 1/100 of a carat.

When you buy diamonds it is often mentally economical to break the price of the stone down to a per carat basis. A rather crude example would be if you were buying drugs you would break the price of a kilo down into a gram weight to establish what you are actually paying per unit. The same is true in diamonds. You should divide the weight of the diamond into the price to get the carat weight.

The next thing to realize is that carat weights do not follow a linear progression in terms of price. There are certain man-made break points in diamond pricing. The first break is at .50 (1/2) of a carat. The second break is at 1 carat and then succeeding breaks occur at each carat thereafter.

These breaks, although arbitrary, are valid and a diamond that is .52 of a carat will cost considerably more than a diamond that is .44 of a carat. A diamond that is over 1 carat, say 1.03 carats, will cost considerably more per point or per carat than would a diamond that is .94. Because this break is so critical, one should always see a diamond weighed in front of one on a scale that has been verified by using an accurate unit of measure. In other words, put a one gram weight on the scale and see if it actually reads one gram.

Because of the price involved, these break points are quite important and one does not want to pay the price differential for over a 1 carat diamond for one that's actually a couple points under. When it comes time for resale, the next buyer will not be so generous in his consideration of the weight.

These price breaks are very substantial and are one of the few things in diamond selling that is not subjective. As such they are quite evident in all diamond sales. The difference per carat weight in a diamond that weighs from 1 to 2 carats may be as much as $1,000 per carat or more, on a 2 to 3 carat diamond. This holds true on a 3 to 4 carat diamond also. One could expect to pay not $1,000 more but $1,000 per carat more. This tends to increase as one gets into the heavier weights and good grades of stones because the stones become much rarer. It is much easier to find small good stones than it is to find large stones of the same quality.