Diamond Carat Weight

Diamond Size: How much does carat weight influence the price of a diamond?

The first factor of the 4 Cs that most people learn is carat weight, which is the best indication of a diamond's size. Let's take a minute to cover carat weights in detail to understand how it effects the price.

Carats
Diamond weights are measured in "carats." One carat equals 1/142nd of an ounce, or 1/5th of a gram. In other words... there are 142 carats in 1 ounce and 5 carats in 1 gram.

The word "carat" comes from the ancient practice in India (where diamonds were first discovered and traded) of measuring diamond weights with the one thing in nature that is both small and the most consistent in weight -- the carob seed. Thus the name "carat" evolved in the English language, which is still equivalent to approximately the weight of one carob bean.

A carat is a unit of weight for diamonds and other gems. The metric carat of .200 grams, or 200 milligrams was adopted in the United States in 1913 and now standardized in the principle countries of the world

Points
You also may have heard jewelers talking about "points" when discussing diamond sizes. This does not refer to the number facets on a diamond, but rather to its weight. Just like one pound is divided into 16 ounces, one carat is divided into 100 points -- so each point is 1/100th of a carat. A "10-point" diamond weighs 1/10th of a carat, and a 50-point stone weighs one-half carat.

Price
Carat weight has a great deal of influence on the price of a diamond -- more so than one might imagine at first. Since larger stones are more rare in nature, they are more expensive as well. For instance, one diamond weighing 2 carats will always cost much more than two diamonds of the same quality weighing 1 carat each.

Below is an approximate comparison of the major diamond weights to act as a starting point in your consideration.

Diamond Sizes

IMPORTANT: Monitors vary widely.
Hold an actual dime over the picture of one below. If the dime below is actual size, then the diamond sizes in this chart are accurate for your monitor.

In jewelry pieces with more than one diamond, the carats may be described in terms of total carat weight (TW). This is the combined total weight of all the stones in the piece.

Diamonds can range in size from a fraction of a carat to several carats. Given the rarity of large stones, however, the price increases rapidly with size; therefore, a single 2-carat diamond will cost much more than two 1-carat diamonds. Very large diamonds with good color and clarity are very rare.

Expect to pay a premium for stones that are above a full carat weight. For example, a .95 carat diamond will cost a bit more than a .90 carat stone.

Because round brilliant cuts follow exact standards, you can make a good estimate of the carat weight of the stone based on the stone's diameter. The following chart compares the relative sizes of stones and describes how much a round brilliant diamond of a certain size is likely to weigh. This chart is for educational purposes and represents a guideline for diameter and carat weights. It is not representative of other cuts or shapes. It is also not applicable to colored gemstones which have a different density from diamonds.

DIAMOND CARAT WEIGHT

.03 carat	.05 carat	.07 carat	.10 carat
2.0mm diameter	2.5mm diameter	2.7mm diameter	3.0mm diameter

.15 carat	.20 carat	.25 carat	.33 carat
3.4mm diameter	3.8mm diameter	4.1mm diameter	4.4mm diameter

.40 carat	.50 carat	.65 carat	.75 carat
4.8mm diameter	5.2mm diameter	5.6mm diameter	5.9mm diameter

.85 carat	1.00 carat	1.25 carats	1.50 carats
6.2mm diameter	6.5mm diameter	7.0mm diameter	7.4mm diameter

1.75 carats	2.00 carats	2.25 carats	2.50 carats
7.8mm diameter	8.2mm diameter	8.6mm diameter	9.0mm diameter