How to Tell How Many Carats a Diamond Is?

Sharif Khan
Sharif Khan
Last Updated    EST 
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Diamonds are sold with a carat (ct.), a unit of weight. Today, the carat is exactly 0.2 grams (around the weight of the thrombus). Carat weight is not related to the comparable sound of karate, which refers to the purity of gold.

Two diamonds of the same carat weight can have very different costs, depending on other factors (such as cut, color, and clarity). To understand the significance of carat weights, if the receiver's heart is set to a diamond of a specific size, the carat's weight is probably the essential factor in the search until you reach the desired size.

As the carat size increases, so does the price of a diamond because the bigger the diamond, the rarer.

Two diamonds of the same shape and carat weight may appear in various sizes, depending on the cut quality. A deeper cut diamond has a large part of its total weight "hidden" deep, resulting in a smaller diameter than a well cut diamond.


  • "Total weight" is different from carat weight since it represents the total weight of diamonds in a piece of jewelry. For example, a pendant with 3 set diamonds will have a total weight of 1.23, implying that all three diamonds weigh 1.23 Carats.
  • When the size is necessary, one should compromise on clarity or color, not the cut quality, since it plays a more important role in a diamond's sparkle, fire, and brilliance. 
  • Choosing a smaller diamond than a full carat, i.e. 0.95 carat can save you money. 

Diamond Carat Size Comparison

Two diamonds of the same weight in the carat can also have very different sizes, depending on the diamond shape. For example, the 1-carat code appears larger than the 1-carat round. The following table illustrates why; for each diamond chart, the following is shown:

Size Estimate: The diamond-shaped images represent an approximation of the right size of an excellent 1 carat cut for each shape. Visually, longer forms (ovals, awnings, pears, emeralds) seem larger than round and square shapes.

Measures (Length X Width): The measurement corresponds to the form mentioned above and is a characteristic of diamonds of excellent size with a weight of 1 carat.

Crown Area (total area (mm2)): The area shows the diamond's actual size with the front side up (as it appears on the ring). For example, while the oval diamond image is larger than a circular image, the actual surface is the same for both shapes, which means that the difference in size is a perception, not a reality. On the contrary, the oval appearance has a greater appearance than the size of a princess cut. Its surface is larger (about 10% higher in this example), which means that the difference is not only an illusion created by an elongated shape.

Diamond Cut Chart

Diamond Size Is Important

It is essential to distinguish between size and weight. Diamonds are sold in carats, though it does not necessarily equate to "more carats equal a bigger size." The cut of the diamonds can play a big part, and the naked eye, along with the tricks light plays, can fill in the rest. For instance, a Round Brilliant can be the same size as a pear-cut but look smaller because of its shape and cut. Also, a one-carat princess cut may be about five and a half millimeters in diameter from the top, while a heart-shaped cut is closer to seven millimeters across the top. Again, it does not mean that one will look more prominent than the other until we learn about each stone's cut grade.

Even if diamonds have an identical shape and weight, they are not necessarily similarly sized. Diamond carat size is determined by how it is cut (dimensions) and its depth. A diamond with less depth has a larger diameter (size) and vice versa—doubling diamond carat weight does not double size since the diamond is larger in both diameter and depth.

diamond sizes chart

Shape Counts Too

Each shape has a unique look. Diamonds that weigh equally but are cut into different shapes will have different sizes (diameter and depth), which is why some shapes appear "larger" than others. The preference for shape is individual. Most diamonds are cut "Round," but many shoppers prefer other shapes.

The Cut Quality

Cut quality greatly influences appearance. A well-cut diamond looks like a "Fireball" and seems larger because weight and dimensional size are optimal and correlate. The worth of a well-cut diamond is also higher because of the incredible difference from other ordinary-looking diamonds.

Carat Weight Classes

Diamond Carat Weight Main Classes Are:

  • 0.50-0.69CT
  • 0.70-0.89CT
  • 0.90-0.99CT
  • 1.00-1.49CT
  • 1.50-1.99CT
  • 2.00-2.99CT
  • 3.00-3.99CT
  • 4.00-4.99CT
  • 5.00-9.99CT
  • 10.00 CT and up

Price differs by percentage between weight classes, so the best-value diamonds are close to the upper limit of the weight class below your target. For example, a 0.94 Carat diamond will look very similar to a 1.00 Carat diamond but will cost between 8 - 20% less (when color, clarity, and cut are the same).


Total Carat Weight or Carat Weight Total describes the total weight of all the diamonds in a piece of jewelry. For example, a diamond pendant with a dozen diamonds may have a ctw of 2 carats.

Another thing to remember when buying a diamond based on carat size is balancing quality and size. You can find a larger, high-quality diamond by selecting a slightly lower diamond color and quality grade. Diamond carat can be hard to tell to the unaided and inexperienced eye by merely looking at it.

Background on Carat Weight

Diamonds are the most expensive and highly anticipated gems the rich expect to have, graded according to the 4 Cs—Color, Carat, Clarity, and Cut.

Carat refers to the mass of the diamond; one carat is about 200 milligrams. Diamonds with less than one carat are commonly considered equal to one-hundredth of a carat (0.01 carat or 2 mg)—generally, the price per carat of a diamond increase directly proportional to carat weight.

The word "carat" originated from the Greek word keration, which means "fruit of the carob tree." In ancient times, the carob pod seeds were used as a standard for weight measurements since their seeds' size was almost always identical. Therefore, it is also the term used to express the weight of a diamond.

Ct is the abbreviation of a carat, referring to the weight of a single stone. It expresses the total weight of multiple stones used in a piece of jewelry. The weight of smaller diamonds is called points. There are 100 points in a carat—another way to look at it is to say that each point equals 0.01 or one-hundredths of a carat. For example, 0.25 means twenty-five one-hundredths, so that a 0.25-carat diamond would equal twenty-five points of one-quarter of a carat.

Diamond carats are often confused with stone sizes even though they measure weight, so people think a higher carat means a bigger diamond. The cut of a gemstone can make it appear larger or smaller than its actual weight. As a result, it is possible to have two diamonds of the same carat weight appearing in two different sizes. When a gemstone is cut in appropriate sizes, the maximum light is returned from the top, making it appear larger. In a poorly cut diamond, much of its weight may be hidden in its base, making it appear smaller than its weight would imply.

It makes sense that the more carats a diamond has, the more expensive it is. But it is not as simple as saying that a 1 carat stone costs precisely half as much as a two-carat one. It would be called "thinking rational" when nothing about diamonds is rational. A 1 carat stone, for instance, costs far more than twice that of a half-carat stone—and so forth—because larger diamonds are rarer than smaller ones. While pulled out of the earth, smaller assorted diamonds are likelier to be found as big, whopping ones. Therefore, larger single stones are expensive, given their weight.

A good rule of thumb to remember is that the closer you get to each subsequent carat, the more expensive the diamond will be. Let us suppose that you have a 0.8ct stone. Logically, you would think that getting the full carat might not be much of a jump in price, but indeed it is. Moreover, the difference between a 0.9 stone and a full carat is somewhat outrageous.

Other FAQs

Question: Is Carat the Size of a Diamond?

Answer: While it is often confused with the size, a carat is the weight of a diamond. While the size of one carat is the equivalent of 200 milligrams, it is usually communicated in terms of "points." Diamonds are measured based on a 100-point scale. Therefore, a .50 carat diamond is also called a 50 point or 1/2 carat diamond.

Question: How is the Size of a Diamond Determined?

Answer: The size of a diamond is evaluated by viewing it from the top or via a birds-eye view. The perspective is used because it represents how the diamond will appear when it is set on the band. For an accurate reading of the diamond size and carat weight, both should be measured with the diamond cut grade and the distance across the top of the diamond (in millimeters).

Question: Is there a Scale that Determines the Size of a Diamond?

Answer: Yes, carat weight is categorized in the following manner:

  • Quarters: .25 carat or 24 - 29 points
  • Thirds: .33 carat or 30 - 39 points
  • Two-fifths: .40 carat or 40-49 points
  • Half a carat: .50 or 50- 59 points
  • Three-fifths: .60 or 60 - 69 points
  • Three-quarters: .75 or 70-79 points
  • Four-fifths: .80 or 80-89 points
  • Nine-tenths: 90 - 99 points
  • Carat: 100 points

Question: Is the Pricing of Diamonds Correlated to the Point Scale?

Answer: The pricing of diamonds is a tricky subject. Since larger diamonds are rarer, the cost of these diamonds is often considerably more. Diamond prices significantly increase at the full- and half-carat weight classifications. Diamonds just below these weights usually cost significantly less, and because carat weight is distributed across the entirety of the diamond, slight size differences are almost impossible to detect.

Question: What are the Factors that Affect the Pricing of Diamonds?

Answer: The appearance of a diamond also affects its price tag. In addition to the carat, the shopper must consider the remaining three of the four Cs in terms of diamond ring pricing. The color, cut, clarity, and how it is mounted significantly impact the pricing and value of a diamond carat ring.