Videos related to the subject of Carat Weight

Here is GIA's quick 1 minute video on the subject of diamond carat weight then we'll delve into some more crucial data.

Carat Weight. The easiest of the 4C’s to grasp. Most people generally associate carat weight with size and to a degree this is true but there’s quite a bit more to learn about carat weight than simply size. Let’s address the obvious first.


Carat weight is merely the weight of the gemstone which is most accurately determined by weighing the diamond on a digital balance (properly calibrated of course) which weighs the gem material down to 1/1000th of a carat.

The term “carat” is an expression of weight used to specifically describe the weight of gemstones.

The metric carat is the equivalent of 1/5th of a gram or .200 gram. Carat Weight can also be expressed in units of “points” as well. To put it simply …

  • 1/2ct = 50 points or .50ct
  • 3/4ct = 75 points or .75ct
  • 1 carat = 100 points or 1.00ct
  • 1 ¼ ct = 125 points or 1.25ct
  • 1 ½ ct = 150 points or 1.50ct
  • 2 carat = 200 points or 2.00ct

Pretty self explanatory.

The best way to understand carat weight as it relates to “size” via the web is to view these various carat weights against a standard of measurement so first we'll take a look on a ladies hand, size 5 1/2 US standard. The diamonds are the relatives sizes ranging from a 1/2ct up to 2 1/2ct.

1/2 carat

1 /2ct

3/4 carat

3 /4ct




1 1 /4ct


1 1/2ct


1 3/4ct




2 1/2ct


Here are the same diamonds alongside of each other and with a dime in the picture to give you another perspective of their relative size. 


Now that you have a grasp on carat weight as it relates to size there are a couple of other important factors to learn about and consider when it comes to the subject of Carat Weight.


Yep. You can have two diamonds of the same weight yet look and be different in actual millimeter size.

In this first scenario you have here two 1ct round brilliant cuts. Note that the diamond on the left looks smaller than the diamond on the right yet they are both 1ct in size. In fact the diamond on the right weighs precisely 1.00ct and the diamond on the left weighs 1.01ct!


The reason for this is because of issues pertaining to the cut quality of the first diamond as it is cut too deep and looks smaller for its weight. We’ll get deeper into the subject of cut in that tutorial but the graphic above is 1 great demonstration of why it pays to get a superior cut over an inferior cut.


Another important factor to keep in mind with regards to Carat Weight is that once you reach certain magic numbers in the weight the prices of diamond can take a notable jump in value.

The numbers, at least with regards to engagement ring sizes are …

  • .30ct
  • .40ct
  • .50ct
  • .70ct
  • .90ct
  • 1.00ct
  • 1.50ct
  • 2.00ct
  • 3.00ct

What this means is if you have 2 diamonds that are both comparable in quality and one weighs .94ct and the other weighs 1.01ct … even though the difference in size is negligible the difference in value can result in hundreds or even thousands.

Understanding Pricing Reports

Each week pricing reports are released on diamonds in our industry and primarily broken down into categories of Carat Weight based on the magic numbers listed above and reflecting what certain carat weight, clarity and color combinations are trading for on the market. Below is an example of a report.


You’ll note 8 blocked off tables on the Report listing various weight ranges starting from .90-.99ct and up to 10.00 – 10.99ct. This happens to be page 2 of a Report as page 1 lists pricing from .01ct up to .89ct.

Let’s zoom in on a set of these tables and I’ll expound.

Rap 2

Note that in the table on the left you have the weight range of 0.90 – 0.99ct and in the table on the right 1.00 – 1.49ct. Each table represents pricing in hundreds of US dollars what any given weight, clarity & color are “listing” for. Going back to our 0.94ct vs 1.01ct example … let’s say we were comparing G VS2 qualities in each size range and we are seeking to determine the listed value difference. Here are the steps we’d take.

Note the table in the .90-.99ct range where G VS2 intersect. You’ll see that a diamond in this carat weight, clarity and color is listing for 63 or $6300 per carat. $6300 x 0.94ct = $5922. When we look at the same quality in a 1.01ct we’d look at the table on the right and note that where G VS2 intersect we find diamonds in this size range are listing at $8400 per carat x 1.01 = $8484.

$8484 - $5922 is a difference of $2562.

The primary reason I’m pointing this out in the carat weight tutorial is because once you’ve learned about the various qualities of diamond and you’ve honed in on a certain clarity and color you really want to purchase but find that it is more than what you can afford, sometimes by dipping approximately a tenth of a carat less in certain weight ranges can mean getting the quality you want at no great sacrifice in size.

BTW here is what a .94ct looks like alongside of a 1.01ct.


Since I have introduced you to pricing Reports in this chapter, as we conclude our tutorial on Carat Weight I should also make some clarifications concerning pricing reports that are vitally important to know.

  • The prices listed on the Reports are rarely ever the actual price a diamond is traded for on either the wholesale or retail level.
  • The listed prices do not take into account cut quality. Only carat weight, clarity & color. Differences in cut quality can impact value by up to 40%.
  • Gemological issues can impact value by notable percentages such as surface breaching inclusions, black inclusions, graining levels, color tone, etc. which can’t be determined from a lab Report (even GIA).
  • The prices really vary when comparing diamonds from different labs. Anything other than GIA or AGS are generally going to be priced at more of a discount and it's not because Reports from other labs are better buys. It is generally because they are not graded as strictly.
  • To use our 1ct G VS2 listing for $8400 per carat for example and at the time of this publishing it is possible to search online for such a “carat weight, clarity & color” and find values ranging from the mid 3k range upwards to the high 9k range based on these variables plus others and why we encourage purchasing from resources such as ourselves who can show you precisely why a diamond holds the value it does and whether it’s really worth your dollar or not.

In conclusion, while carat weight is generally the easiest of the 4C’s to understand and is pretty straight forward there are some little tricks here than can help you save time, money and lots of headaches.