top of page


Surprisingly to some, the carat size of a diamond actually refers to its weight — not size.

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. Not to be confused with “karat” which is the measure of purity for gold and platinum, Carat 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 weight may be different mm sizes.

One (1) carat = 200 milligrams. Diamond weights are usually expressed digitally as 1 carat = 1.00 carat. The carat is 100 “points”. This is why you see diamond weight referred to as 0.52 or 0.78 or 1.25 carat. This allows for exact weights to be compared. For example, a diamond commonly called a ½ carat diamond may weigh from 0.47 carat to 0.52 carat. By using the digital 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 versus a 1.00 carat, can mean a significant difference in price while not necessarily meaning a significant difference in appearance.

Diamond Size Chart

The illustration below shows the approximate diamond size of each weight



“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 you can but you shouldn’t. The diamonds in a pair of earrings need to be matched for size as well as weight color and clarity. As we have said size can vary within a weight so diamonds of the same weight may be two different sizes that will be noticeable when mounted.

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

No. At Clean Origin and most other jewelers, diamond studs are marked by total weight. So, for example, a 1CT (or 1CTTW) pair of studs contains 2 diamonds of 0.50 CT each. They have also been matched in size, clarity, and color to each other for the perfect pair.

“Does one diamond shape look bigger than another but have the same weight?”

Sometimes certain fancy shapes, like an oval or pear shape, may look slightly larger but still be the same weight as a corresponding round. 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, has a very different look than 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?”

According to The Knot, one of if not the foremost wedding planning and resource website, in 2019, more than half of all engagement ring sold in the U.S. contained a center diamond between 1 – 2 carats

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

The only certain method is to weigh the stone. Even a jeweler can only estimate by appearance alone and when mounted this is even more difficult.

“What size is a 1-carat diamond?”

Because cut quality varies any particular 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 1-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 of equal quality to mined stones are 25-40% less in price. 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 size does not precisely equal weight 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.

bottom of page