Carat is the unit of measurement for the physical weight of diamonds. Diamond Carat is often confused by the term ‘size’ but it is actually the measure of a diamond’s weight and a reflection of its size.
In simple terms, Carat is the weight of the diamond, how much a diamond can weigh. And the diamond weight of One carat (1ct) equals to 0.20 grams (200 Milligrams).

Understating Diamond Carat – 4cs

Each Carat of a diamond is divided into 100 points for accurate measurements where one point is equal to 0.01 carat.
Therefore, a Half-carat (1/2) diamond can also be described as 50 points OR 0.50 carat diamond and One Fourth (1/4) carat diamond is called as 25 points OR 0.25 carat diamond in terms of Carat weight. Whereas Diamond weights greater than one carat are expressed in carats and decimals. For E.g. a 1.08 carat stone would be described as ‘one point oh eight carats.’

After determining Cut, Color, Clarity of the 4c’s, Carat becomes the most appealing factor in choosing a diamond. Because that decides the final value of a diamond. Diamond prices increases with the diamond carat weight. Larger diamonds are always more precious and desirable. But it is important to know that 2 diamonds of equal carat weight vary in prices depending on the other 3 factors of diamond (Cut, Color, and Clarity).
Hence, the 4^th C, Carat has least impact on diamond’s appearance but it’s the primary factor to calculate the price of a diamond.

Changes In Diameter (MM) And Price As Per Carats Size

To understand diamond pricing we have to take one example stone. Lets take G Color, Vs1 Clarity, Excellent Cut for below four diamonds. Please note price of a diamond is determined on many factors beyond 4 cs.  Below table is just to give your basic idea about diamond pricing with change in size.

Carat Weight	Size	Diameter (MM)	Price Per Carat	Total Price
0.50 ct		5.1 mm	3000 $	1500 $
1.00 ct		6.4 mm	6000 $	6000 $
2.00 ct		8.1 mm	12000 $	24000 $
3.00 ct		9.3 mm	18000 $	54000 $

The above table depicts how the diameter and prices increases with the carat weight.

Firstly, let’s understand the % Increase In Diameter (MM) as per the Carat Weight
There is a common misunderstand that half a carat (0.50) is half the size of one carat (1.00) but the fact is half a carat is just half the weight of one carat. However, the Diameter (millimetre) difference is not the half of it. For instance, The measurement for a Round 0.50 ct diamond is 5.1 mm while the Round 1.00 ct diamond measures at 6.4 mm so the millimetre difference on a round diamond is 1.3 mm which is only 25% (from 5.1 mm to 6.4 mm) Thus, this shows even if the carat weight doubles, diameter does not increases with the same percentage.

Now, let’s see the Relationship between the Price and Size of a Diamond
From the table, we can see the price increases with the higher carat weight. For instance, when the carat weight gets tripled (from 1.00 ct to 3.00 ct ) prices per carat also get tripled(from 6000$ – 18000$). But total value of diamond jumps very high with increase in size. For example total price of 0.50 ct diamond is 1500$ ( 0.50 x 3000 $), where as price of 2 carat is 16 times more of 0.50 ct stone ( 2.00 x 12000 $). Increase in size of diamond means more rare and thus expensive.

How Carat Weight Points Affects the Price

Diamonds are generally cut to a rounded number 0.70 OR 1.00 ct rather than  0.69ct OR 0.99ct. But it is the most important to understand to prefer 0.98-0.99 ct over 1.00ct. The difference in size will be negligible, but you can save a significant amount.

For instance:  If you buy a diamond that weighs 0.98 carats, it would cost $ 5880 (0.98 x $6000). But if you buy a diamond that weighs 1.00 ct, it would cost $8000 (Assuming diamond has same Cut, Color, and Clarity) so here 0.98 pointer can costs nearly 25% less than a carat. Hence it is highly recommended to consider points as they cost less than diamonds whose weight has been rounded up.

To conclude, if the cut of a diamond possibly has the greatest impact on the overall desirability of a diamond, the carat has the heaviest impact on its pricing. And as diamond increases in size and carat weight, the price will increase at an increasing rate because larger diamonds are rarer and thus more valuable.

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