Carat Weight

glowing diamond

1.00 Carat Round Diamond

Carat weight is often seen as the most important factors in choosing a diamond. So, what’s really meant by a 1 carat diamond or a 2 carats diamond? Technically speaking, one carat is equal to 200 milligrams or 100 points. If you purchased a 1 carat stone, it means that you had bought yourself exactly 0.2 grams of diamond.

Like many others, I guess you are probably thinking why a diamond’s weight is measured in terms of carats. Isn’t the use of SI units like the kilogram or its derivatives better suited to describe the weight of something so expensive? Why not the use of ounces which we are familiar with in everyday life applications? 

Well, the history of this actually has an interesting background to it. The word carat actually originates from carob; which refers to a locust tree that produced edible pods. Carob seeds, being even in weight, were used as weighing references by traders in the olden days. Remember, this was a time when high tech machines were not in existence. Back then, one carat was equal to the weight of one carob seed and trades were made based on this simple estimation.

As you could have imagined, carob seeds varied in sizes and everybody was using different references depending on which part of the world you are in. Back in the 1890’s, if you bought a “one-carat” diamond, the weight could actually vary anywhere between 0.94 to 1.06 metric carats! That’s a huge amount of uncertainty considering the amount of money paid for a single stone.

Much as changed since the ancient times. Highly sensitive weighing equipment have replaced the carob seeds but the industry stuck with the terminology using carats as a means to describe the weight of a diamond.

carob seeds used for measurements

Without electronic balances, seeds were used as measurements

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Why Is Carat Size Perceived as the Most Important Factor?

I’m sure you guys are familiar with this scenario. What’s the first reaction or question that comes to your mind when hear about a new diamond jewelry purchase? Without a doubt, questions associated with “What’s the carat size/weight of the diamond?” would instantly come to mind.

The main reason behind this is that the size of a diamond corresponds directly to the value and worth of the piece of jewelry. And in many societies, it is an indication of a person’s status and wealth. On top of that, we have also been conditioned by mass media advertising campaigns into believing that bigger is always better.

Ads with catchy bylines like “Make your lady fall in love with a 1 carat diamond”, “Love is as big as it gets” etc… are all smart marketing tactics that jewelry companies employ to create a desire for bigger rings. In fact, cliché movie lines like “If you loved me, you would have bought me a bigger diamond” had been so much overused that the underlying meaning had been mentally etched in the minds of many consumers.

suite of 3 different rings

How big is big enough? Where do we draw the line?

The truth is that jewelers know diamonds sell for more when they go pass certain sizes. It is no coincidence that the majority of diamonds in the market are cut to retain as much rough weight as possible at the expense of brilliance and beauty.

How often have you seen stones that weigh 0.48 or 0.99 carats exactly? By design, such stones are rare oddities because they fall below the “magic sizes” that can fetch more money. Instead, what you would observe is that the bulk of the stones would usually be cut to nice figures like 0.50 or 1.00 carats. Most of the time, this is done by compromising cut quality as the cutters strive to keep as much rough as possible.



With that said, don’t get carried away with choosing the biggest stone that you can find. This is one of the most common and yet, gravest mistakes that first-time buyers make. What precedes focusing on how many carats a gemstone possesses is also a consideration of its cut, color and clarity. We will be covering some aspects of that with detailed examples of diamonds in the following pages.

Coming up, you can use the following carat size chart diagrams and tables to help visualize the physical size of a diamond. These charts are really helpful if you are new to diamond shopping and want to gauge the exact dimensions with respect to a corresponding weight.

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  1. Ryan-
    July 27, 2015 at 12:07 pm

    Do you have any tips on calculating diamond weight in carats or estimating how heavy it is based on dimensions? I’m considering to buy an antique ring that doesn’t have any certificate. The problem here is that the owner herself doesn’t know full details as well. If you could shed some advice, it would really be appreciated.

  2. Paul Gian-
    July 29, 2015 at 7:13 pm

    Unfortunately, there’s no easy way to do it accurately if the stone is mounted. The estimated weight would be within a range and would at best be an educated guess. You probably need to consult an appraiser where they can use professional tools to measure the stone. They will also have the necessary knowledge to calculate and provide a fairly accurate weight estimate.

    The more important issue I want to highlight is that you are buying an uncertified diamond. You won’t know for sure what you will be getting and you are subjecting yourself to unnecessary risks. My advice is: stay away.

    If you are looking for a vintage diamond ring, this page will probably interest you:

  3. Michael Guilas-
    June 12, 2016 at 8:27 am

    The gentleman is asking how to know the diamond well enough because he want to purchase the vintage ring. My concern is why are you discouraging him not to buy the ring that he want? What I can see here is you are using diamond learning website to get a customer for yourself. Please post your comment.

  4. Paul Gian-
    June 12, 2016 at 3:15 pm

    This website is specifically to help consumers make smart decisions and stay away from unethical vendors/scammy deals. Would you buy a vintage ring yourself without knowing FULL details? The solution is to take the ring to an independent appraiser or better yet, simply look for another vendor who can offer all the required information in the first place.

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