Diamond Carat Weight

It is a given that most people would prefer a large diamond. However, there are a few factors that play into how large it appears against how heavy the stones carat weight might be. As one of the basic 4C's of assessing a diamond, it is important to understand exactly what carat weight entails in order to select the perfect stone.


 Two Blue Diamond Heart shapes

Two beautiful heart shaped fancy blue diamonds


The weight significantly affects the cost of the stone since the cost is increased considerably per carat. For example, a 1.00 carat diamond is not exactly half the price of a 2.00 carat diamond. If the weight drops, even if it is only by a few points down to the lower carat weight, the price of the stone will be significantly lowered.

*HINT * When looking to purchase a new diamond, try to find one that is as close to the next carat weight as possible. For example, a stone that weighs in at 1.91ct will cost significantly less than another diamond that weighs in at 2.00 and higher even though it is only a difference of 9 points. The difference in size can be extremely difficult to see and the cost will be quite noticeable. Only, locating diamonds in these sizes are quite difficult since cutters will often do whatever possible not to drop to a lower carat weight.


The Definition of Carat Weight and its History

A carat refers to the unit measurement used to describe the weight of the diamond. Many years ago, because of their size, the seeds of the Carob were used on precision scales as units of weight for small quantities of precious stones. This tradition continued through time, hence we refer to the unit measurement as carat.


Read more about the definition of carat weight and its history.


Carat Measurement

Diamonds that come with a grading report will indicate the exact weight to the nearest hundredth of a carat weight. Each carat is divided into 100 points, so if a diamond weighs 3/4 of a carat, meaning 75 points, its weight would be recorded as 0.75 ct. In the industry, the price of a diamond is often referred to by the price per carat (price per unit of 1.00) and is written as P/C (per carat) as opposed to the overall cost of the stone.


A GIA diamond certificate


Read more about how to read and understand the GIA Certification of Colored Diamonds.


Fancy color diamonds are already such a rare find. Needless to say, finding a large stone, especially in rarer colors such as Red, Blue, or perhaps even an Argyle Pink diamond is therefore much harder to come by and will be significantly more valuable.

Carat Weight vs. the Size of the Stone

The carat weight and the size of the stone definitely have a lot to do with one another. However there are a number of factors that are different between the two.

Regardless of how heavy the diamond weighs, when someone looks at a diamond they often concentrate on the size of the table. Since the table is what everyone other than the jeweler assessing the stone will see, this is the most important aspect of the diamonds appearance.


Relative to the diamond boxes shown in the image below, the face value size of each of the stones are quite similar between one another. However, as seen in the image, the carat weight is significantly different between each of the diamonds as a result of the depth of the stones.


 The impression diamond depth has on the size

The image above displays specifically what affect diamond depth has on the appearance of the diamonds shown. From left to right: a 0.45ct stone with a 28% depth, a 1.24ct stone with a 46% depth, 0.56ct stone with a 58% depth, and a 1.14ct stone with a  70% depth.


The 0.45-carat, pear-shape diamond in the image above has an extremely shallow 28% depth. As a result, it possesses a very large face value size, although it contains a large window in the middle of the stone. The 1.24-carat, pear-shaped diamond has a 46% depth. This is also quite a shallow stone and it includes a small window in the face of the stone. The 0.56-carat, pear-shaped diamond has a 58% depth, which is closest to the most common norm of 60%. The 1.14-carat, pear-shaped diamond has a 70% depth. With such a deep depth, even though it is 1.14-carats it appears somewhat smaller in size although the color of the stone is a little more intensified as a result of the light being trapped within the stone for a longer period of time.


Learn more about carat weight vs. the size of the stone.


Carat Weight vs. Clarity, Color and Overall Diamond Quality

There are times when if a stone includes an external blemish that can likely be removed, or through advanced polishing techniques the color can be maximized, the choice might be made that it is worth taking the risk of putting it back on the polishing wheel. Doing so will most often reduce the size of the diamond, but can result in a higher quality stone.


For example, Leibish & Co. was lucky enough to have won six diamonds in the 2011 Argyle Pink Diamond Tender. One of the stones, a 1.71 Fancy Intense Purplish Pink Diamond, was truly a magnificent piece. However, when Shmulik Polnauer, Leibish & Co.’s GIA Graduated Gemologist, bid for this stone it was because he saw something no one else could.


Shmulik spoke of the time he spent assessing that stone. Even though it already passed the hands of some of the most experienced diamond polishers in the field, he was convinced that if we won that diamond he could maximize its true potential even further. Upon receiving word that the stone was won, Leibish & Co. took the risk of placing that diamond back on the polishing wheel. The Leibish Prosperity Pink Diamond was repolished into a breathtaking 1.68ct Fancy Vivid Purplish Pink Diamond.

 The Leibish Prosperity Pink Diamond, 1.68-carat, Fancy Vivid Purplish Pink, Radiant-shaped diamond

Leibish & Co.'s 1.68ct, Fancy Vivid Purplish Pink Prosperity Pink Diamond

The example given above is specifically why some experienced diamantaires may take the chance of re-cutting a polished diamond. Only three points were lost on that diamond, but the overall diamond quality was significantly improved.

Learn more about carat weight vs. quality of the diamond.


The Size vs. the Shape

The piece of jewelry you choose and the setting in which you place the stone will have a significant effect to the appearance of the size of the diamond. Also, certain shapes always look larger than other shapes even though they might be a lower carat weight. For example, an Oval shape will look longer then a Round shape and will appear to be bigger. A Marquise shape, due to the longish look, also reflects a big appearance in comparison to the other shapes.

The two stones below look quite different in size as a result of their shapes, but there really is only 28 points between the two!

 3.11-carat, Fancy Deep Grayish Blue Cushion and a 2.83-carat, Fancy Grayish Blue Emerald

3.11-carat, Fancy Deep Grayish Blue, Cushion and a 2.83-carat, Fancy Grayish Blue, Emerald


Also, the many variations of the same shape will appear different from one another with regards to the size. For example, the stones below present a different face up value between a Square-cut Radiant, a longer Square-cut Radiant, a Regular style Radiant, and a Rectangular-cut Radiant.


 0.34-carat, Fancy Intense Blue,Rectangular Emerald, VVS10.22carat, Fancy Pure Red, Emerald, SI10.50-carat, Fancy Vivid Puplish Pink0.25-carat, Fancy Dark Yellow Orange

0.34ct-Fancy Intense Blue, 0.22ct-Fancy Purplish Red, 0.50ct-Fancy Vivid Purplish Pink, 0.25ct-Fancy Deep Yellowish Orange


Many characteristics affect the appearance of the stone. For example, a colorless diamond that is cut very well, in a way that light can quickly pass through, will actually appear slightly bigger from the sparkle. Fancy colored diamonds work the same way, only the cut should cause the light to remain within the stone for as long as possible to help accentuate the color.


The four attributes (AKA the 4Cs) define the scientific guidelines of assessing the diamond quality, and therefore define the overall value. However, especially with regards to color diamonds, beauty is always in the eye of the beholder.


Contributor: Benji Margolese

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