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A Complete Guide to Diamond Carat

by Staff

When you start shopping for a diamond engagement ring, you’ll quickly become accustomed to hearing about the 4Cs: cut, color, clarity, and carat weight. While these all define important aspects of a diamond, the carat weight is one in particular that many shoppers pay close attention to.

What Is Diamond Carat?

Diamond carat refers to the weight of the diamond and a metric carat is 200 milligrams. It’s also related to size, but carat weight and size are not the same: two stones with the same shape and carat weight can look very different depending on the cut.

To learn more about diamond carat and how it affects your jewelry purchase, we spoke to two experts: Hannah Florman and Jen Oliak, who taught us everything about how important carat really is, how it impacts the cost of your diamond, and how to get the best deal for a larger size.

Meet the Expert

  • Hannah Florman is a private jeweler in Boston who specializes in one-of-a-kind diamond engagement rings and fine jewelry.
  • Jen Oliak is a third-generation jeweler and the owner of Ounce of Salt Jewelry.

The Importance of Diamond Carat

The importance of diamond carat is mostly subjective, but what diamond carat really influences is the price of the stone. According to Oliak, “carat weight is often the most important aspect of the 4Cs used in determining the price of a diamond.”

That said, diamond carat is really as important as you want it to be. “If you prioritize a very large stone, carat weight may be at the top of your must-have list,” Florman says. Those who don’t feel that a larger stone is a necessity may find that other aspects of the diamond are more important than the carat weight.

How Carat Impacts the Cost of a Diamond

In general, the higher the carat is, the higher the diamond price is. “If all else is equal (cut, clarity, and color), a diamond’s price increases with diamond carat weight because larger diamonds are more rare and more desirable,” Florman says. “However, two diamonds of equal carat weight can have very different values depending on the other three Cs.”

In other words, diamond carat definitely has a significant impact on the cost of a diamond, but it is not the only determining factor in price. You could have a diamond that has a high carat weight, but if the clarity isn’t fantastic and the color is less than great, the price will go down.

How Carat Impacts the Size of a Diamond

Many people assume that diamond carat equals diamond size, which isn’t true. The carat weight refers to the mass of the diamond, and the cut can really influence the size more than the carat.

“Believe it or not, a higher carat diamond with a poor cut can appear smaller than a smaller carat diamond with a better cut,” Florman says. “For example, a one-carat round diamond is not half the size of a two-carat diamond. A one-carat round will average 6.4mm in diameter, and a two-carat will average 8mm.” This is why Florman stresses the importance of not discounting smaller carat weight.

How Diamond Carat Is Weighed

Jewelers use scales to measure diamond carat, and the process is very simple. “All you need is a highly calibrated scale capable of measuring very small weights,” Oliak says. “Organizations like the GIA or AGS will have very accurate scales.”

The Carat Point System

Jewelers typically use a point system when discussing carat weight, and it’s not something that is often expressed to buyers. Still, it’s helpful to know if it comes up. “Within the diamond industry, you might hear people refer to a stone as having x-number of points or an x point,” Florman explains. “If you think of a carat weight as equal to 100, each point is .01 of a carat. So a 90 pointer is another way of referring to a .90 carat diamond.”

As Oliak explains, it’s just a way to express diamond weight for very small diamonds. As a buyer, what you’re more likely to hear is that a stone is, for example, one carat, two carats, or three carats.

Shopping Advice and Money-Saving Tips

A lot of buyers are intent on making diamond carat their number one priority because many feel that a larger carat weight is automatically more impressive. There’s nothing wrong with wanting a larger carat weight, but it’s important to know that, as Oliak says, “bigger doesn’t always mean better.” You’ll find that the highest quality diamonds are exceptional in each of the 4Cs, not just carat weight. Don’t ignore the other three Cs just so you can get a larger diamond—that might lead to you purchasing a diamond with hidden inclusions, poor color, or a dull sparkle.

Florman also stresses that carat weight isn’t the be-all, end-all of diamonds. She suggests looking for slightly smaller carat weights for a lower price point. “The difference between .10 carat is indistinguishable to the untrained eye, but can make a considerable difference in price,” she says. “‘Magic Sizes,’ as they’re called in the diamond industry, are sizes that are particularly popular, and therefore more expensive. For example, a two-carat stone may be significantly more expensive than a 1.90-carat stone that looks very similar.”

If you have your heart set on a larger carat size but you’re still working with a budget, Oliak recommends choosing a diamond shape with a larger face, such as a round brilliant shape, which looks the largest among diamond shapes due to weight distribution.

If you’re willing to trade cut for carat, you should choose a shape that is more forgiving on diamond quality to the naked eye.

“For instance, an emerald shape diamond has a ‘step cut’ with less facets than a round brilliant,” Oliak says. “This allows inclusions in the stone to be seen with the naked eye much easier than a stone with a round brilliant (many facets) cut.” You can choose an emerald with a larger carat size and a lower clarity because that clarity will lower the price without being too obvious.

Florman says that if you’re going to prioritize the carat weight over another C, you should “keep an open mind and let your private jeweler hand-select some stones.”

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