Carat Weight

An important aspect of a diamond is its weight. Diamonds are measured in carat and 1 carat equals exactly 0.2 grams. Please note that carat refers to the weight and not the size of a diamond! But in general the size of a diamond increases together with its weight.

 The word carat is actually derived from the word “Carob” which is a specific bean of the locust tree. As Carob seeds were believed to be very even in their weight distribution these seeds were used to measure fine jewellery in the past. This however is a factual inaccuracy but it still goes to show that myths can survive for very long.

For today’s standards this seems like a very unreliable method to measure the weight of a diamond. Still, the word carat survived.

Carob beansDo not mix up diamond carat for weight with gold karat for measuring gold purity though!

Gold fineness expressed in karats comes from carats and grains of gold in the ancient roman solidus coin. One solidus coin used to be 24 carats which was preserved up to this date.

Is carat weight the most important factor when buying a diamond?

No, and I hope you already know that!

A diamond is all about looks, brilliance, fire and scintillation. All these characteristics are determined by the diamond cut! Only a diamond with Excellent cut proportions will provide you with the maximum of brilliance that you should be looking for.

Of course, if you have a diamond with a great cut, more carat weight will make the facets of the diamond appear larger which in turn will return more light and sparkle to the viewer’s eye.

Still, it should be your main priority to make sure that you get the best possible cut so that you can then adjust the carat weight accordingly.

Far too many people are focused on the carat weight because this is the first question that you will likely be asked by relatives and friends. For many people it is a matter of prestige to be able to say that one’s diamond has at least 1 carat in weight. In order to make the diamond affordable many people therefore compromise on the cut. I would advise that you do not do that!

Why exactly is the cut more important than the carat weight?

I want to demonstrate this fact to you by showing you the two outlines of two different diamonds. Both diamonds are exactly one carat in weight.

impact of the depth on the diameter
The diamond on the left side has a pavilion depth of 66.4 % and thus a lot of hidden weight in it. The diamond therefore only measures 6.2 mm in diameter. The diamond on the right side however has only a depth of 61.7 %. This is the optimal depth according to super optimal diamond cut proportions!

This results in the diamond being 6.5 mm in diameter. This makes a very noticeable difference as with every mm more in diameter the surface of the diamond increases exponentially (you might remember the formula π * r² back from school). A larger surface means more light being returned to the viewer’s eye and thus a larger amount of brilliance, sparkle and scintillation!

Thus, by choosing a better cut your diamond appears larger and thus seems to have more carat weight. You would therefore wonder why there are people out there who pay more attention to carat weight than to the cut grade! Sadly, these people are mostly misinformed or they don’t really care about the beauty of the diamond but just want to be able to say that they bought a diamond with such and such carat weight.

How does an increase in carat weight affect a diamond?

The carat weight of a diamond impacts both the price and the size of a diamond. A diamond with two carat does not appear twice as large as a diamond with one carat. This is due to the fact that most of the diamond weight is retained within the depth a diamond.

round diamonds carat size chartIf you want to have a general idea of what the diamond with your specific carat weight will look like mounted onto a ring setting you can use the James Allen carat size simulator.

James Allen Carat Size Simulator

Furthermore, the price per carat increases exponentially. This is simply due to the fact that any finished diamond is yielded from only one piece of rough diamond. To obtain a bigger diamond the rough diamond will also have to be bigger. As large rough diamonds occur far more rarely in nature than its smaller counterparts, the prices increase accordingly. This is why 1 carat diamond rings are surprisingly more expensive than for instance 0.9ct diamond rings.

Here is a table I have created with round cut diamonds that I have found on James Allen with all the same parameters in cut, color, clarity apart from its carat weight. As you can see the price increases exponentially:

All other things being equal the price of a diamond increases exponentially the more carat a diamond has

All other things being equal the price of a diamond increases exponentially the more carat a diamond has.

On the next page you can discover more about the diamond color…

Read Next: Diamond Color

Carat Weight
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Sebastian Naturski loves to write about diamonds and share his knowledge with his readers.
When he is not working on his website he is studying law at Humboldt University of Berlin.
He has taken part in several international law competitions and likes to broaden his horizons.
His other big passion are languages. He is fluent in German, English, Polish and Japanese and got basic skills in French and Spanish as well.


  1. Thanks for the post.
    I actually wanted to take a Very Good cut so that I can afford a a diamond with above 1 carat.
    But now I think I will rather try to save money on color and if possible on clarity.

  2. Hey Sebastian
    great information, i am in the process of looking for the right ring for my fiance. Your website is really helpful so i can choose the right one.

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