Carat Weight - and its impact on the price

Carat weight is probably the best known attribute of diamonds. But what is behind it? In this article I will explain how important carat weight is within the 4 C's, how the exact mm to carat conversion is and how the carat number affects the price.

But first to the history of this measure: Carat comes from the word "Carob". Carobs are the seeds of the Locust Tree, which grows in the Mediterranean region and the Middle East. You wonder what seeds have to do with diamonds? Nothing really, but it is said that the Carob seeds grow unusually alike and therefore almost always have the same proportions and weight. That's why the seeds were used as a measuring unit. One Carob weighs about 0.2 grams.  I will come later to the exact carat to gram conversion.

Wrong usage of carat weight as a quality attribute

When you buy an engagement ring and have proposed, the first question all friends ask is: Wow, how much carat is that? This has strengthened the impression that carat is apparently THE indicator for a diamond. It seems to be very important. Bullshit!

Personally, I think most people just don't understand much about diamonds and carat is the quickest thing to get stuck in their heads. "Somehow carat has something to do with size and somehow it also influences the price." So everybody wants to shine with this dangerous half-knowledge. Besides, all the stars always boast about dozens of carat diamonds, which makes it a dream for many girls to be like their heroes. Who does not have the desire to wear a 1 carat diamond on her finger? Doesn´t sound fresh saying “my diamond is 0,75 carat”, right?

So first of all from my side: Please do not let this confuse or influence you. After studying and understanding everything about diamonds, you will realize that carat weight is the last factor to be included. So just let the others talk...

How important is Carat Weight?

The truth is that carat has no influence on the quality of the diamond. Let's approach the matter logically: as the name suggests, carat weight is about the weight of the diamond. It is important to understand this. It is not about size or shape. But who can see weight? Especially when the diamond is in the setting, you can only see the surface, nothing more.

Once again the importance of the Diamond Cut

In this chapter we will come back to the importance of a brilliant diamond cut. As explained above, you can't see the weight of the diamond and also the size inside the setting is not really visible. But what you do see is the surface and, with a good cut, the sparkle that shines towards you. In the article about the diamond cut I go into detail about the proportions and important elements of the cut and how they influence the appearance. Nevertheless, it should be said that it is much more important to buy a good cut than to give too much importance to high carat numbers.

Diamond Cut vs Carat Weight

MM to Carat Conversion

Especially when buying diamonds online, it is extremely important to be able to estimate the size of the jewel. A huge diamond on a thin finger does not always look good. On the other hand a small diamond on a very large finger can disappear as well. Therefore it is important to think about how big the diamond should be in the end. As an example you can see the proportions of the round shape:

Of course there are significant differences depending on the shape of the diamond. For this reason I have shown you the mm to carat conversion for each individual diamond shape in a separate article. Here you can also compare the individual diamonds per carat and per shape. Just take a ruler at home and make yourself familiar with the sizes.

Carat To Gram Conversion

Now we come back to the Carob seeds. The unit of carats was measured and determined exactly on one seed:

Little excursion into mathematics:
1 carat = 200 milligrams

So with 1 Carat Weight, one speaks of a mass of about 200 milligrams, that is 0,2 gram. And of course this implicitly influences the size, but depending on the shape of a diamond you don't see the difference between 0.8 carat and 1 carat. Especially not when the diamond is in the setting and half of it is buried anyway. In addition, every shape has to be cut differently. So with increasing weight, more mass has to be processed and also consumed to cut the diamond into a certain shape.

How Carat Weight influences the price

We have clarified that carat has no influence on the quality of the diamond and where this unit comes from. But what influence does carat weight have on the price?

That is easily explained: the more mass you buy of something, the more expensive it gets, because more raw materials are needed for the production. It’s the same correlation for diamonds. A heavier diamond with more mass requires more raw material from which the diamond can be cut. With increasing consumption of raw materials the price will rise.

Price impact Carat Weight

For this reason, carat weight is the last characteristic that should be selected. Only when you have found the perfect cut, the optimal clarity grade and the right shape, you should fill up the rest of your budget with carat. The bigger the diamond, the more impurities and diamond inclusions you will see. Do not let anybody convince you to buy a large diamond if the clarity grade is not sufficient. For this purpose, I have also described all clarity grades in detail in the chapter diamond clarity what you should pay attention to. Especially if your budget is not very big, you will inevitably come to the SI1 vs. VS2 comparison, where I will gladly help you.

0.9 Carat vs. 1 Carat - how to save a lot of money

Never underestimate how fast the price grows with increasing mass. For this you can look at and compare a few examples under James Allen - Diamonds.

But what comes on top of the pure mass is the value for certain prestige factors, such as the desire for 1 carat, 2 carat, 5 carat...

These are all the high performers among the sales figures, as they became famous through stars or rich people and everyone wants to have such smooth carats if they can pay for it. But to save money, just look at the 0.9 carat diamonds. I'm sure you can't see the difference between 0.9 carats and 1 carat, but there are huge leaps in price. Now compare these two diamonds from James Allen (both VVS2, H Color, Excellent Cut - for more details click on the images):

So we're talking about 2.000 dollar that can be saved in this example. Think about whether it really has to be exactly 1 carat or whether you wouldn't be happy with 0.9 carats and save a lot of money.

At a Glance

It's from the "Carobs", the seeds of the locust tree. Almost every seed is similar to the other one.

It's only important for your pocket. Within the 4 C´s it´s the lowest one. The most important one is the diamond cut, so check this one before.

The mm to carat conversion is different for every diamond shape. Get familiar with my converter for every shape!

1 carat = 0,2 grams = 200 milligrams

Definitely! The more carat the more raw material you will need to cut the diamond out of it. So with every carat more the price will increase due to the material and the cutting efforts. 


You can see again: different shapes lead to a different look and size in mm of the diamond. That means that you don't always have to pay for 1 Carat if it looks oversized at the finger of your girlfriend. Let's take the example that you want to buy a pear diamond. Just compare the mm and optics to a round diamond of the same carat weight. Could be that a smaller pear diamond looks better due to the visual size. If you want to go deeper into the mm to carat conversions please read my article about it.

So it is important that you first think about the other 3 C's and then check how much space is left in your budget, which you fill up with carat. But always keep in mind that diamonds on different fingers and women look different and maybe your fiancée is not a fan of giant diamonds. Then you are not making her and your wallet happy with it.
Set your budget, determine your desired quality and see how much budget is left. After that, you can, if you want, take more carat weight than originally planned. But for the look it is important to get the best possible cut. Therefore you can read my article about the Diamond Cut and its implication on the quality and price of a diamond.
I know, for many people it is the magic number if my diamond has 1 carat, but always ask yourself if this is necessary considering your budget. If you don't have a limit then go for it and enjoy it. There is nothing more beautiful than a diamond that you can look at in its full glory. But if you have a limit, just keep the price in mind.