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Matt Ubertini GIA Gemologist At DreamStone

By Matt Ubertini
Staff Gemologist

Matt has a vast experience working with top diamond manufacturers and jewelers in NYC's diamond district for over 18 years. With graduate gemologist degrees from the Gemological Institute of America and International School of Gemology, Matt uses real world examples to help simplify the understanding of diamonds.  

The first thing you need to know about "carat" is that it refers to the diamond's weight. There is a correlation between weight and size, but it is not directly proportional to how a diamond appears since carat weight can be distributed differently throughout the stone. For example, you can have two cushion cut diamonds of equal weight, each 1.01 carat, appear to be different sizes:


5.90 X 5.47 mm

larger measurements

6.25 x 5.52 mm

What appears as the “size” of a diamond is actually it’s length and width. Checking out the millimeters across the diamond from the top is key. This information is available in any grading report as length mm X width mm X depth mm. We’re focusing on the first two numbers. With that said there is an opportunity here to get a smaller diamond that appears bigger and save a bundle of cash. This is because the carat weight has the biggest impact on price. The price for the same diamond increases substantially for every carat range. So how can we possibly get a nice size diamond without breaking the bank? To understand how you can save money with this price structure, let us turn the tables and sit in the seller’s chair for a minute. Suppose you were a diamond manufacture and you happen to buy a 2 carat rough diamond. You examine it carefully and determine this rough gem will yield 1 carat polished round diamond, H color, Si2 clarity, but it is not so cut and dry, you have a big decision to make. You have an alternative option to cut a little more of the original carat weight to clear out a tiny fraction of inclusion and end up with a smaller diamond at 0.90 carat, H color, but get an Si1 clarity grade (one grade higher clarity). You do the math on both finished options and see which option will gain you a bigger sale. A quick market search reveals a round 0.90, H, SI1 trades for around $4,000 dollars while 1 carat, H, SI2 trades for about $4,700. If money talks and clarity walks, then you would most likely opt for the 1 carat mark that gets you the bigger bucks.

Now, lets switch back chairs and worry about our own pockets. From your perspective you can get a higher clarity, same color diamond that is just a hair smaller for less money. So when you see the diamond you want that’s just under the 1/2 carat mark, 1 carat mark, 1.50 carat, or 2 carat mark, etc… with a 0.40 carat, 0.80-0.90 carat, 1.30-1.40 carat, or 1.70-1.80 carat accordingly since they may just have similar measurements across the top and could save you money. The industry calls these “off sizes,” (a good thing). Here are some measurement comparisons with approximate prices for round diamonds:

Excellent Cut

0.90 Carat, I Color, SI1 Clarity

Higher Color, Just Under A Carat

Price: $3,500

Very Good Cut

1.00 Carat, J Color, SI1 Clarity

Lower Color, at 1 Carat

Price: $4,400

1.29 Carat, G Color, VS2 Clarity

Higher Color & Higher Clarity

Price $7,894

1.50 Carat, H Color, SI1 Clarity

Lower Color & Clarity at 1.50 Carat

Price: $7,875

1.70 Carat, F Color, VS1 Clarity

Just under 2 Carat

Price: $15,775

2.01 Carat, F Color, VS1 Clarity

Same Color & Clarity at 2 Carats

Price: $22,521


Regardless of a diamond’s proportions some people just want a 1 carat diamond, 2 carat diamond, or 3 carat diamond. Reaching the whole carat mark is meaningful and there is nothing wrong with that. After all, they do have higher resell values.