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Diamond Carat Weight: Size Matters

by Clean Origin
Last updated on October 16, 2023

Surprisingly to some, the carat size of a diamond refers to its weight — not its size. To make things even more confusing, the terms “diamond carat size” and “diamond carat weight” are actually synonyms. They both refer to the diamond’s weight.

All About Diamond Carat Weight

The fourth ‘C’ in diamonds is carat weight. The term “carat” was originally derived from the carob seed, which in ancient times was the standard used by traders of precious gems. It’s easy to confuse this with “karat,” which is the measure of purity for gold and platinum. Diamond carat weight, though, is the weight of a diamond or gemstone. Carat always refers to weight (not size), as depending on the cut, two diamonds of the same carat weight may be different mm sizes.

One (1) carat equals 200 milligrams. Diamond weights are usually expressed as 1 carat = 1.00 carat. The carat is 100 “points”. This is why you see diamond carat weight referred to as 0.52 or 0.78 or 1.25 carat. This allows for people to compare exact weights. For example, a diamond commonly called a ½ carat diamond may weigh anywhere from 0.47 carat to 0.52 carat. By using the decimal system. you know the EXACT weight of the diamond you are considering. Also, if all other qualities are equal, the greater weight of a diamond, the greater the cost. However, even small differences in weight, such as a 0.95 carat diamond versus a 1.00 carat diamond, can mean significant differences in price while not necessarily meaning significant differences in appearance. If you’re looking for larger diamonds– or at least diamonds that appear larger— there are several factors to consider.

diamond carat weight

Diamond Carat Size Chart

The illustrations below show the approximate sizes of various diamond carat weights. Keep in mind that this graphic is specifically for a round diamond, as the same carat weight in another diamond shape may appear larger or smaller. 

diamond size chart

Now that you understand the meaning of carat weight, we must emphasize again that in the valuation of any diamond, the weight is only one element of the 4Cs to be considered.

Our experts at Clean Origin will be glad to assist you in evaluating all our diamonds for the one that will be perfect for you!

Lab Grown Diamonds’ Carat Weight

The carat weight of lab-grown diamonds and mined diamonds is determined in exactly the same manner, as both have the same mineral content. While it is theoretically possible to produce lab grown diamonds in almost any carat weight, the most common carat weights available are between 0.30 carat and 6.00 carats.


“Can I just get two (2) carat diamonds of the same weight with the same color and clarity and make a pair of earrings?”

The short answer is that you can but shouldn’t. The diamonds in a pair of earrings need to be matched for size as well as diamond carat weight, color, and clarity. As we have said, size can vary within a weight. So two diamonds of the same weight may have a size difference that will be noticeable when mounted.

“If I buy a pair of diamond studs that are 1.00 CT, is that 1 diamond carat each?”

No. At Clean Origin and at most other jewelers, we mark diamond studs by total carat weight. So, for example, a 1CT (or 1CTTW) pair of studs won’t have a one carat diamond on each one. The pair contains 2 half carat diamonds instead. The diamonds match each other in size, clarity, and color to each other to make a perfect pair.

“Do certain diamond shapes look bigger than others but have the same weight?”

Sometimes certain fancy shapes, like an oval or pear, may look slightly larger but still be the same carat weight as a round diamond. However, you still want to remember to take the other 3 C’s — cut, color, and clarity — into consideration, as some of the fancy shapes, such as emerald, have a very different look from a round brilliant.

“How much does a diamond carat weigh?”

1 (one) carat = 200 milligrams or 0.2 grams or 0.007 oz.

“What is the most common diamond carat weight used as a center stone in an engagement ring or other diamond ring?”

According to The Knot, one of the foremost wedding planning and resource websites, more than half of all engagement rings sold in the U.S. in 2019 contained a center diamond that was between 1 – 2 carats.

“How do you tell how many carats a diamond is?”

The only certain method is find out how much the diamond weighs. Even a jeweler can only estimate by appearance alone, and when the diamond is mounted, this is even more difficult.

What size is a one carat diamond?”

Because cut quality varies, any particular carat weight of a diamond will vary in size from stone to stone. However, a well-proportioned 1 carat should be approximately 6.5mm.

“How much is a one carat diamond?”

Weight is only one factor in the price of any diamond, whether mined or lab grown. Therefore, the price of a one carat mined diamond can vary from $500 for a very poor quality stone to over $10,000 for a diamond of exceptional color and clarity. In general, lab grown diamonds are 25-40% less expensive than mined diamonds of the same quality. It should be noted that very poor-quality lab grown diamonds are seldom offered for sale, while poor color and clarity mined stones are available at some dealers for what may appear to be SUPER discounts. However, when it comes to so-called “deep discounts,” it is good to be wary and keep in mind the old adage “you get what you pay for.”

“What is the most common center stone size?”

Since we know that physical size does not precisely equal actual carat size and that most engagement rings sold in the U.S. have center diamonds between 1-2 carats, we can approximate that the most common diamond center stones are between 6-8mm.