Your Quick Guide to Understanding Diamond Carat Size


If you are in the market for a loose diamond or an engagement ring, there is a good chance you have come across the term "diamond carat," one of the 4 C's of diamond education.

Today we are giving a quick guide on what a diamond carat means and how it might affect your loose diamond or engagement ring purchase.

At Jianna Jewelers, we work hard to empower our customers with knowledge, as we believe an informed purchase is the best kind there is. We are very proud of the education we give to our customers as we know that with knowledge comes power.

Diamond sizes and how diamonds are measured are the most commonly discussed aspect of any diamond. It's easy to understand why since it's the first thing you'll notice when viewing a stone.

Diamond carat size is on many wish lists, and it's in every headline when a celebrity gets engaged. But have you ever wondered what carat size really means?

Read below for a breakdown of the carat weighing system used for diamonds and why the weight of every diamond is unique. 

Why Carats?

Carats (ct) are a unit of mass used to weigh diamonds, gemstones, and pearls. The carat is a very old standard of measurement that extends back to at least the 16th century for measuring diamonds. The carat probably has its origins in the carob seed used in Greek and Roman times as a standard form of small measurement. Even though we think of a carat as measuring the size of a diamond this is not the case. The carat is a weight measurement so the appearance of two stones that are both 1-carat diamonds can be somewhat different.

Today, a carat is equal to 200 milligrams. This standard of measurement was adopted early in the 20th Century by the General Conference of Weight and Measures (Confrence gnrale des poids et mesures ? CGPM). Interestingly, the CGPM, established in 1875, is the same organization that established the metric system and encouraged its adoption throughout the world for the standardization of all weights and measurements.

Each carat is divisible by 100 points, each weighing 2 milligrams. Prior to the standardization and adoption of the carat system different countries used slightly different standards of measurement for diamonds and gemstones making it very difficult to compare one stone to another without placing them side by side. The adoption of the carat meant that a diamond seller in Africa and a diamond buyer in Brussels could reach an agreement concerning a particular stone much more easily.

However, the carat system has its limitations because diamonds are shaped and cut differently. A 1-carat diamond can be cut long and deep and it will look visibly smaller than a diamond that is cut shallower. The different cuts of the stones, for example, cushion, round, marquise, square, emerald or pear will also weigh different amounts because the cuts are different. In other words, how the stone is cut and its shape can have a dramatic impact on the presentation of the stone.

The size of a diamond dramatically influences its price. This is where the carat becomes a very valuable tool. Larger diamonds are rare compared to smaller diamonds so the price per carat substantially increases based on the weight of the stone. For example, a 5 ct diamond may cost $45,000 per carat while a smaller stone of less than 1/2 ct may cost $2,400 per carat for a diamond that is graded the same in all the other categories. For further information about diamonds and to see how stones in different sizes look, please use the free interactive tools on our diamond education page.


"Jianna Jewelers has amazing products and the quality of their work is amazing. I bought my wife's engagement ring from them and we both loved their work so much we got all of our jewelry for our wedding from them from our rings to a custom hand crafted diamond necklace! Beautiful store and Great service too. They are definitely our jewelers for life." P P. on Yelp

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