What Is a Diamond Carat?

Last updated on September 1, 2024

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When it comes to the value of a diamond there are four main factors that come into play. These factors are referred to as the four C’s and include clarity, color, cut and finally carat. It is this final C which we are going to focus on today.

What Is a Diamond Carat?

You may have heard the term carat before (the spelling in North America is “karat”) in terms of gold. In this instance it refers to the purity of gold. As an example 24k gold is considered pure gold and means that there are no other metals included in the material.

Lower quality gold such as 18k may include metals such as copper, nickel, silver or palladium mixed in with the gold making it less pure and as a result less valuable. When the term carat is used for diamonds however it does not refer to purity.

Technically speaking all diamonds are completely pure because they are made entirely of carbon so we don’t have the carat with a "k" in this case. A diamond carat refers instead to the weight of the finished diamond.

A single carat in diamond weight is roughly 1/5 or 0.2 of a gram in actual weight. Specialized, very sensitive scales are used to weigh these diamonds and their weight in grams is then divided by 0.2 to get their weight in carats.

As an example a 0.4 gram diamond would be assessed as being 2 carats. This is a pretty average size for an engagement ring gemstone if not a little on the higher end of the range.

The carat weight of a diamond has an impact on the stone's value with the price growing exponentially as the diamond size increases. The reason for this is that most rough diamonds are small; it is rare to find a large rough diamond that can be cut into a large finished diamond.

The largest solid diamond in the world is called the Cullinan I or the Star of Africa I. In its finished state this diamond weighs 530 carats and came from a single rough diamond that weighed 3,106.75 carats. That rough stone was cut into 9 large diamonds and several smaller ones.

In terms of value the Star of Africa 1 is estimated to be worth more than $400 million and is currently part of the scepter that belonged to Queen Elizabeth II. It is a controversial piece with many calling for the gem to be returned to Africa where the original rough diamond was discovered.

How To Choose the Right Size Diamond

There’s something about hearing that sharp intake of breath followed by the words “Look at the size of that rock!” A big diamond without question is impressive and would be considered a real status symbol. When it comes to choosing the right size of diamond this is an entirely personal decision.

If you want the largest gem you can afford then that is great and totally your decision but allow me to play devil's advocate a little bit here. You say bigger may seem better but if you are looking for maximum sparkle good things come in small packages.

Bigger diamonds, even those cut in the most light capturing ways possible just do not sparkle as well as smaller ones.

The reason for this disparity is that when light has to travel further inside the diamond it loses some of its eventual impact. It will still sparkle just not with the same ferocity. So if you want that maximum sparkle you should look to stay in the 1 – 1.9 carat range.

Is the Cut as Good With Large Diamonds?

This is something to be considered. When you spend your budget on a larger diamond you may be sacrificing gemstone quality. As an example a larger diamond with fair cut quality may cost the same as a smaller one with excellent cut quality.

The smaller diamond will have much better sparkle and the larger one will look drab in comparison. Bigger yes, but drab nonetheless.

Be smart with regards to your diamond size choice because although you may think it will look better if it's bigger you can lose out on so much brilliance.

Does Carat Weight Have the Biggest Impact on Value?

This is a very good question because yes the bigger the diamond the more it should cost, in theory. Large diamonds are rare. That said, a large diamond that is of poor quality in terms of color, clarity and cut may not be as valuable as you would think.

A slightly bigger diamond will always lose out to a smaller diamond with better clarity, less color and a superior quality cut. It’s not just the size, it's the quality of the gemstone that matters and in fact a bigger diamond is not always the place to spend your gemstone budget.

Final Thoughts

Carat weight is an important factor when it comes to diamonds because big stones are rarer. There are some epically huge diamonds out there worth millions of dollars which the average person would be lucky to see on television let alone in person.

A single carat does not amount to much weight roughly, it's the same as five normal-sized paper clips actually. Sometimes a diamond that looks small may also be very dense and technically be considered heavier in terms of carat weight.

The weight of a diamond, although important, is not always the yardstick that commands the greatest value because size only counts if the quality of the gemstone is also present.

Reference Diamond Size Chart

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