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Diamond Carat Weight

~ Carat Weight Explained ~

Carat is the standard measurement used to show the weight in not only diamonds, but in all gemstones. However it’s the one aspect of the 4Cs that fool many people.

All though all 1 ct. diamonds (should) weigh the same, not all 1 ct. diamonds, or any size for that matter, are cut equal, so they can look very different.

Carat is the unit of measure used to describe the weight of a diamond, and is probably the most misunderstood of the 4Cs, as carat refers to the actual weight and not the actual size of the diamond. Let me explain.

Same carat weight but different size

All three of the diamonds above are 1 ct. in size. Meaning they all WEIGH .2 grams. However if your friend has a proportionate 1 ct. round diamond, and you compare your deep cut 1 ct. diamond to it, you'll swear you've been taken to the cleaners. That's because not all 1 ct. diamonds, or any size for that matter, are cut equal. In fact the picture below is what you're actually looking at.

Carat Weight Combined with Diamond Cut

Diamond cut being the most overlooked of the 4Cs is actually one of the most important aspects of choosing a diamond. If you do not understand diamond cut, then you may be disappointed in the diamond you purchase. Because you want your 1 ct. diamond to look like the carat weight you purchased, and equally important, you want it to sparkle.

Just a word of caution. No matter what carat weight you're in the market for. Be sure to look at the diamond's cut. Try to keep to the excellent and very good cut grades if it's possible. It's even better to sacrifice carat weight in place of cut. If you neglect this one detail, the results could be what you see to the right. You want the one in the middle, not the dull one to the left and especially not the nailhead looking diamond to the right.

Combining Carat weight with diamond cut

The size to weight difference


You'll notice that a 1 ct. diamond is not double the size of a .50 ct. diamond. Although the weight has doubled, the size has two aspects to it. The diameter and the depth. As the weight increases the carat weight is dispersed through out the diamond. This is why a proportionate 1 ct. round diamond will have a diameter of 6.5mm, and a proportionate .50 ct. round diamond will have close to a 5mm. diameter.

Is your diamond close to ideal "carat weight" proportions?

Here's some charts to follow. You'll notice the carat weight and diameter size. Try and find a diamond that is as close to that diameter size as possible for the carat weight and shape you desire. It's a great way to gauge the cut of the diamond.

Princess diamond carat weight chart
Round diamond carat weight chart
Emerald diamond carat weight chart
Asscher diamond carat weight chart
Marquise diamond carat weight chart
Oval diamond carat weight chart
Radiant diamond carat weight chart
Pear diamond carat weight chart
Cushion diamond carat weight chart
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How is Carat Weight Usually Represented

There are three ways in which diamond carat weight can be used.

  • Point System Think of it like a dollar bill to pennies. There's 100 pennies in a dollar, there's 100 points in a carat. So a .53 carat diamond could be stated as a 53 point diamond. If you have a 2.53 carat diamond it could be stated as a 253 point diamond.
  • Abbreviation The most common way. An example would be ".85 ct." diamond. Which is an 85 point diamond.
  • Fraction You'll also see fractions used. Such as 1/4 carat for a .25 ct. or 25 point diamond.

How Carat Weight is Represented as a Group

Other ways that Carat is spoken / written about is the sum of all the diamonds in the group, ie... wedding ring. This is typically stated as CTW (carat total weight) CWT (Carat weight total) DWT (Diamond total weight). For instance.

You can interchange ctw. with cwt. Both mean the same thing. You can use just cts. if you're talking about a single diamond solitaire.

Price Difference in Carat Weight

I'm sure you've noticed from looking online that many diamonds with the same carat weight are far from consistent in terms of price. This is because of 6 things.

  • Cut of the diamond
  • Color of the diamond
  • Clarity of the diamond
  • Who graded the diamond
  • Rarity
  • Promotions & Sales

If fact, often times, you'll find smaller carat weight diamonds can be more expensive than their larger carat counterparts. This is because of the 6 items mentioned above in an almost unlimited combination. For instance, you could have a .90 ct. round diamond with E color, VS1 clarity and excellent cut, be more expensive than a round 1.04 ct. H color, SI1, good cut diamond.

Interesting Facts


The carat weight of a diamond is very crucial that even a fraction of difference in weight can make a considerable difference in price. That is why each diamond is measured out to the 1000th of carat and rounded up to the nearest 100th of a carat. In other words, a grading lab weighs a diamond and finds it to be 1.788 cts. This would be rounded up to 1.79 cts.

Carat vs Karat

Is Karat the same thing as Carat? No. Karat is used to describe gold (10K, 14K, 18K, 24K). Carat is used to describe the weight of a diamond. Actually Carat is used to describe the weight of all gemstones.

Often times if you'll have carat weights that are within 10-15 points of each other, and all things were equal you would find most of the prices would be relatively close (which makes sense), what makes each price different is the quality, and that quality can actually increase a diamond's price by thousands. Making a diamond with similar carat weight exceed the price of the larger closer carat weight.

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Grading Labs and Carat Size

Here's an important scenario. Let's say you have 2 marquise diamonds. Each one is a 1.35 ct., F color, VS2 clarity, excellent cut diamond. The only difference between the two, is who graded it. One could be graded by GIA, and the other by EGL International. Who grades your diamond is EXTREMELY important. GIA is considered the foremost in grading authority. They set the standards by which diamonds get graded. What GIA says your diamond is … it is! However if your diamond is graded by EGL International then it's considered throughout the diamond industry as a hit or miss. As many diamond wholesalers consider GIA to be too strict, so they opt to use another service that grades more "casually" allowing the diamond owner to say their diamond is better than what GIA says it would be, and thus charge more or it (in most cases).

In other words, if all things are equal on the grading certificate, and that grading certificate is from GIA, EGL USA, or AGS, you can expect that diamond to be exactly what is says it is. If however it's not graded by any of the three grading labs above, then you can usually count on that F, VS2 diamond to be more like a H, SI1/SI2 diamond. Any diamond wholesaler knows this. That is why a GIA, EGL-USA, AGS graded diamond is more expensive than another diamond graded by other diamond labs. With the top three labs you know what you're getting. With the other labs that diamond certificate could be off as much as 1-3 grades on color and clarity.

Rarity and Carat Weight

Let's say you have two diamonds. Each one is exactly the same (1 ct. G, SI1 round), in most cases if you combined the total value of both of those diamonds, it will actually be less than one 2 ct G SI1 round diamond. This is because it's much more rare to find a 2 ct. diamond in nature, than it is to find a 1 ct. diamond. And the more rare something is, the more value it holds.