The Ultimate Guide to Diamond Carat

May 02, 2023

The Ultimate Guide to Diamond Carat

When you go to pick out a diamond, you’ll hear a lot about the ever-used 4Cs: cut, clarity, color, and carat. This article dives into that last one - carat. You’ll typically get that word paired with a number, and higher numbers come with higher price tags. Does that necessarily mean you need the biggest-carat diamond possible? What does that even mean?

Keep reading to get the answers to those questions and a few others. By the end, you’ll be better equipped to decide what carat diamond you’re looking for and why. Being better educated makes the hunt for the perfect diamond easier (and more exciting). All knowledge is worth having - especially when it’s tied to such a big investment!

What is Diamond Carat?

Some of the 4Cs get complex. Describing and measuring diamond cut, for instance, is a layered experience. Diamond carat is quite simple in comparison. It’s a measurement of the diamond’s weight.

A 1.0 carat is 200 milligrams, and the GIA divides each individual carat into 100 points for more accurate measurements. Measuring carats isn’t approximate. It’s exact. You might hear carat expressed with a decimal number or with points, but they both amount to the same thing. A .50-carat diamond is a 50-point diamond.

Why is it Important?

Diamond carat is important because it’s the best way to express the size of the stone. Using the number alone, you’ll have a good guess about what it’ll look like. For example, if someone says they’re looking for a four-carat ring, you’ll know they’re interested in a hefty stone! 

Carat is also important in determining a diamond’s rarity and price. Large diamonds (thus, diamonds with high carat values) are very rare. People pay for rarity, and big stones cost more. It’s hardly the only determining factor in that final number, as even a massive diamond with Z-grade color and low clarity isn’t as desirable as other combinations, but its carat size still has a distinct role to play.

How Are Diamond Carats Measured?

As mentioned above, a diamond’s carat score reflects its weight. That’s how it’s determined, and a diamond must be weighed very accurately to get the correct carat size.

Keep in mind, carat only reflects the weight of the diamond, not necessarily its size. The two often correspond, but they’re not the same. When you see any point value or decimal measurement attached to ‘carat’, you’re seeing a reflection of its weight. One carat is 200 milligrams or .200 grams. The math from that point on is simple. A two-carat diamond weighs 400 milligrams, a three-carat diamond clocks in at 600 milligrams, and so on. A diamond can come in at any decimal point in between.

What is the Most Popular Diamond Carat Weight?

One-carat diamonds are the most popular choice for engagement rings. They’re weighty enough to showcase everything wonderful about diamonds, while still coming in at a price range that many people can afford.

Other factors like settings, metal choices, and the other 4Cs influence prices, but you can typically get a beautiful one-carat ring for less than $5000. On average, people tend to spend between $3000 and $5500 on engagement rings, putting them well within the range to take home a one-carat diamond.

What is the Difference Between Diamond Carat and Diamond Size?

While it’s tempting to use these terms interchangeably, they are different. Diamond carat is a measurement of a diamond’s weight, and it’s measured in milligrams. A diamond’s size, however, is its height and width. You’ll see it expressed in millimeters.

While these two measurements are different, they interact closely. You’ll find that most diamonds of a certain carat will fall into a certain size range, depending on their shape. For instance, if you take home a one-carat Princess-cut diamond, it will probably be around 5.5mm, while a one-carat round diamond might be around 6.40mm. There’s always some variation, especially if you purchase a diamond cut by hand (instead of a machine), but there’s a typical range.

diamond carat

A diamond’s size is a good reflection of its cut. If you know what you’re looking for, you might notice when a diamond is cut too deep or too shallow by its overall size measurements. How does that interact with the diamond carat? A poor cut, and thus a skewed size, can make your large three-carat diamond seem smaller.

How Does Diamond Carat Affect Its Value?

Simply put, the heavier the diamond, the more it’s likely to cost. That’s the most basic way to look at it. Large diamonds are rare in nature, so you’ll pay more for something high-carat compared to the equivalent stone with a lower-carat value.

Even if you’re purchasing lab-made stones, high-carat diamonds take more time and energy to produce. As a result, they cost more. There are specific carat weights that influence price more than others. Think of them like thresholds - once you reach it, the price probably goes up (or down) a level. Those weights tend to be even, such as the following. 

  • .50ct
  • .70ct
  • .90ct
  • 1.00ct
  • 2.00ct
  • 3.00ct
  • 4.00ct
  • 5.00ct
  • 10.00ct
diamond carat weight

Price differences between those marks won’t fluctuate nearly as much as they do once you hit the next “big” number. As always, a diamond’s grades in other categories affect its score, too, so carat alone isn’t always an accurate way to estimate price.


A diamond’s carat, or its weight, is critical in determining its value. It’s not exactly the same as size, but it often corresponds with particular sizes. You won’t see a four-carat diamond measuring at 6mm, for instance, unless something is very off.

While carat measurement alone isn’t everything, it’s one of the 4Cs for a reason. It heavily influences a diamond’s overall appearance and price. Look at the differences between carats in person, see how they look with the shapes and cuts you love, and use the information in this article to make the most informed decision about your stone.

Recent Posts
previous arrow
next arrow
This website uses cookies to ensure your best shopping experiencie and track your cart.Learn More