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What is Diamond
Carat Weight?

Carat weight is a measure of a diamond's weight,
and a reflection of its size.

1 carat is equivalent to 200 milligrams. Because carat is a record of a diamond's weight – not its size – two diamonds of slightly different sizes may have the same carat weight. A diamond's size is also dependent on how evenly its weight is distributed, and the quality of its cut. Some diamonds are cut to maximize carat weight, resulting in less sparkle. A balance of quality in carat and cut is therefore recommended.

For the best value, look at diamonds slightly lighter than the carat weight you initially want. For example, instead of 1-carat diamonds, consider 0.98 and 0.99-carat diamonds. The difference in size will be negligible, but savings here can be significant.

Explore the relationship between diamond cut and carat weight.

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When diamond rough is cut to maximize its carat weight at the expense of sparkle, the finished diamond is likely to have a lower cut grade than it might have otherwise. While many shoppers will have a clear idea of the carat range they want in a diamond, it is also important to budget for a quality cut grade. We do not recommend large diamonds with poor cut grades as they simply will not deliver an attractive sparkle.

Diamonds with cut grades of Very Good or above will have angles that produce more sparkle than those with lower grades. These diamonds will not be too shallow, or too deep – proportions that can make the diamond appear dark and dull.

deep cut

shallow cut

Diamonds cut too shallow or deep will reflect
less light and therefore sparkle less.


The carat has been used as a weight measurement for centuries, and is derived from the Greek word for carob seed. It is believed that in ancient times, carob seeds were known for their unusually consistent mass from seed to seed.

While the modern definition of a metric carat was established in 1907 – divisible into 100 points, of 2 milligrams each – it has been used to name various mass values in different regions. In Egypt, for example, 1 carat was 195 milligrams, while in London and New York it was 205 milligrams. Today, the 200-milligram carat measurement is used all over the world.


According to a 2013 study conducted by The Knot, the average diamond carat weight purchased is 1 carat. Step-cut diamonds such as the asscher and emerald cuts often have a slightly larger average carat weight. These shapes are designed with large open tables at the top of the diamond, and typically have a larger depth percentage than round diamonds. This means that, when viewed from the top as set in a ring, these shapes require a larger carat weight to look comparable in size.

Conversely, marquise and pear cuts have elongated silhouettes that allow them to appear larger and have a greater surface area than other fancy diamond cuts that measure the same in carat weight. These shapes are recommended if you are looking for a diamond that seems as large as possible within your budget.

asscher 1.23 ct

cushion 1.20 ct

emerald 1.23 ct

oval 1.19 ct

pear 0.93 ct

princess 1.23 ct

radiant 1.34 ct

round 0.98 ct

marquise 1.08 ct

Choosing your carat weight

When it comes to choosing a carat weight for your loose diamond or engagement ring, it is best to balance personal taste with the need to purchase within a budget. Remember that size is not everything – cut, clarity and color also affect the overall quality and appearance of your diamond.

If browsing our diamond inventory, look for diamonds that are very slightly below the carat weight you consider ideal. For example, instead of just filtering for 1-carat diamonds, explore those at .97 and .98-carats. The difference in size will be negligible, yet you can save significant amounts that can be put towards a better quality setting, or a higher diamond cut grade.

Written by Paul Meiterman, Gemologist at Ritani

Paul Meiterman G.G., A.J.P., C.G. (Graduate Gemologist, Accredited Jewelry Professional, Certified Gemologist American Gem Society) is the Chief Gemologist at Ritani. With over 15 years of experience, he worked in the GIA laboratory as Quality Assurance Gemologist and now works in our factory alongside the top cutters, balancing out size, clarity and proportions for maximum beauty and value, making sure to bring out the best in every diamond.

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