Regardless of whether you're thinking of popping the question with a dazzling diamond ring or you're eyeing up a sparkler as a special gift for a loved one, you've likely come across the term "diamond carat". It's one of the four C's of diamond buying. And as most people would argue, it's the most important factor when shopping for the perfect diamond.

But when it comes to diamond carats, there's a common misconception that carat refers to the size of a diamond. But it actually measures the weight of a diamond. For this reason, you could find yourself looking at two very differently sized diamonds that have the same carat weight. Due to this, it can be hard to know exactly what to look for or ask for when buying a diamond.

Worry not, however. We're here to help simplify things! In this article, we're going to explain everything you need to know about diamond carats, including what the term really means and how it's used to measure diamonds.

We'll also cover the key things you need to be aware of when buying diamonds so you get the perfect show-stopper. So, let's get stuck in!

The carat (ct) is a unit of measurement used to denote how much diamonds weigh rather than their size. It is one of the most important factors that are considered when determining the price of a diamond — the higher the diamond carat weight, the more expensive the diamond. The carat was standardized as a measurement in the early 1900s and was formally adopted in 1907 at the Fourth General Conference on Weights and Measures. This is the same conference that established the Metric System, also known as the International System of Units (SI).

Sometimes referred to as the Metric carat, a carat is currently defined as 200 milligrams split into 100 "points". The reason is that when measuring diamonds, jewelers need an extremely precise unit of measurement. Therefore, diamond carats are weighed to three decimal places and then rounded to two decimal places — E.g. you could have a 0.25-carat diamond.

The word carat can be traced back to ancient times. It's derived from the Arabic word qīrāṭ, which means "bean pod". This comes from the Greek word keration, which refers to the carob bean.

Jewelery sellers and merchants needed a way to accurately and reliably measure gemstones. So, they would use carob seeds to counterbalance diamonds and other jewels on hand-held scales. The reason is that the seeds were considered to be consistent in size and weight and, therefore, an accurate counterweight for diamonds, gems, and pearls.

If a jeweler describes a diamond as being "one-carat", they are referring to the weight of it rather than the size. The Metric unit carat is defined as being 200 milligrams or 0.2 grams, meaning that any diamond that is labeled one-carat will always weigh the same.

However, diamonds can be cut into all kinds of shapes such as oval, heart, princess, round brilliant, emerald, marquise, pear, or cushion. Each of these will show carat weight differently. The reason is that diamond size is a measure of width, length, and depth, which is not correlative to weight (carat).

In fact, often, diamonds that have a high carat will actually be visually smaller than you'd expect. Many diamonds are cut to be deeper rather than wider so that jewelers can capitalize on the increased price that a high carat diamond brings.

But, by doing this, the beauty and aesthetic look of the diamond may be compromised. Not only can depth make a diamond look smaller from the top, but it also means light doesn't refract as well throughout them, making them appear duller and less sparky — the last thing you want when you're picking out an eye-catching dazzler.

Diamonds are one of the most precious commodities on the planet. Therefore, there needs to be an accurate and reliable method of measuring them when deciding on a price. Historically, the carob seed was used as a counterweight when measuring the weight of diamonds, which is where the term carat comes from. The reason is that the seed pods were considered to be uniform in weight and size.

Of course, nowadays, this isn't accurate enough. So, the carat was standardized to form the modern Metric carat that is used for weighing precious stones today. Due to the fact the Metric system is based on decimals, the carat can be split into 100 equal parts. This allows jewelers to weigh diamonds to three decimal places and then round them to two decimal places. As such, it's a highly accurate method of measuring diamonds. Hence why the carat is the universal unit used today.

Determining the carat weight of a diamond is not complicated. The loose diamond is placed on a set of scales and weighed in grams. Then the result is divided by 0.2 to show the carat weight. For example, take a diamond that weighs 0.4 grams on the scales. Divided by 0.2, the value is then 2. Therefore, the diamond is two carats.

It's also important to note that when dealing with diamonds, you may also find that jeweler gives the carat total weight (ctw) instead. This means that the weight given is the combined total carat weight of every diamond in a piece of jewelry.

Yes, the carat weight of a diamond is the most important factor that determines its price. The higher the carat weight, the more expensive the diamond will be. That said, the price of diamonds is not consistent the larger they get. This is because the larger the diamond, also the rarer it is. So a two-carat diamond is more costly than two one-carat diamonds of the same quality.

Furthermore, you'll also notice a big jump in price between some carat weights. Take a 0.90ct diamond and a 1ct diamond. Despite the fact that to the naked untrained eye, there isn't a noticeable difference in size between the two, the one-carat diamond will be much more expensive. The reason for the jump in price is due to the desirability of a 1ct diamond.

How much does a diamond carat cost?

Carat is not the only factor that determines the cost of a diamond. For this reason, a one-carat diamond can range anywhere from $1,800 to $18,000. You may find that a large diamond that is low quality is significantly less expensive than a smaller diamond that is extremely high quality. The reason is that high-quality diamonds are much rarer, which drives their price up significantly.

Not necessarily, as carat simply refers to the weight of the diamond rather than its quality. You could have a higher carat weight that has visible inclusions in it, making it less aesthetically appealing. On the other hand, you could have a lower carat weight with little to no exclusions and a clear color. Therefore, a higher carat does not always mean high quality.

The other thing to remember is that some sizes of diamond are more expensive simply because of desirability. As we mentioned previously, there is a price jump between 0.90ct diamonds and 1ct diamonds. In this instance, you could get a slightly smaller diamond that is of equal quality to the next size up. While the size difference is minimal, you'll notice less of a hole in your wallet!

Finally, it's important to be aware of the other main factors that determine a diamond's quality: cut, clarity, and color. These, along with carat, are known as the 4 C's. Let's explore them in more detail.

The 4 C's of diamonds

When buying a diamond, there are four main factors to consider. Collectively, they're known as the 4 C's. Not only do these aspects quantify quality and visual appeal, but they also determine the price you'll pay for your diamond.

The 4 C's are as follows:

  • Carat: this is a measure of the weight of the diamond. The higher the carat, the rarer the diamond and, therefore, the more expensive it will be.
  • Cut: the cut of a diamond is not how the stone is shaped, but rather how it interacts with the light. A high-quality cut diamond will shine beautifully in the light, whereas a poor cut diamond will look dull.
  • Clarity: diamond clarity is an assessment of how flawless the diamond is. It refers to any blemishes or inclusions that are visible. Clarity is measured on a scale of flawless (FL) to included (I3), with flawless being the rarest and, therefore, most expensive. While flawless diamonds are out of most people's budget range, slightly included (VS1 and VS2) and very, very slightly included (VVS1 and VVS2) diamonds are more affordable while still being visually nearly flawless.
  • Color: diamonds are rated from D to Z based on how colorless they are. D to F rated diamonds are clear and colorless, whereas diamonds rated with letters further down the alphabet are heading toward being yellow. The more colorless a diamond, the more desirable and expensive.

The most expensive diamonds have a high carat weight, and are internally flawless and colorless. But this doesn't mean you can't buy a beautiful diamond on a budget. It's simply a case of determining which aspects are the most important to you and weighing them up to get the best outcome.

Frequently asked questions

How do you choose the right diamond carat?

The perfect diamond carat will depend on who you're buying it for. For this reason, here are some things to consider when shopping for the perfect carat size:
The wearer's finger size: if you're shopping for a diamond ring, you need to consider the ring size of the person you're buying for. If the wearer has larger fingers, a small carat diamond can look insignificant. Similarly, those with thinner fingers may find a huge diamond too heavy and cumbersome. Think about what will suit the wearer best and be comfortable. You may also want to consider the shape of the diamond. While a round diamond may suit one person's fingers, other shapes, such as marquise or pear, may be more interesting and look better.
Size vs budget: the larger the diamond, the more expensive it will be. By balancing quality and carat, you can find a diamond that fits your budget better than simply going for the biggest one you can afford. It will also likely be more visually attractive than a large but flawed gem.
Practicality: bigger isn't always better when it comes to jewelry. If you are purchasing an item such as an engagement ring, think about whether it will be worn every day. While the diamond itself will be hard enough to withstand everyday wear, it's important to remember that the size shouldn't be too large and impractical. On the other hand, if you're looking for a showstopper piece that will be worn for special occasions, you may want to choose a larger diamond.

What are "magic sizes" when referring to diamonds?

Magic sizes are carat sizes that are more desirable and popular. Generally, magic sizes are in increments of 0.25ct, with the most popular one being 1ct. Other common magic sizes also include 0.5ct, 0.75ct, 1.5ct, and 2ct. But remember, choosing a diamond that is slightly under a magic diamond carat size means you can save yourself a large amount of money.

What is the difference between carat and karat?

Although both carat (c) and karat (K) are terms that originate from the same source — the carob seed — they measure different things. Carat is the unit of measurement used to denote the weight of a diamond, whereas karat denotes gold purity.

One karat of gold is equal to 1/24 part gold in an alloy. If you have a 9 karat gold ring, it would consist of 9 parts gold and 15 parts of other metals. In other words, this is 9/24 or 37.5%. The percentage of gold in a piece of jewelry is also stated in the hallmark stamped on it. A 9K gold ring has 37.5% gold in it. Therefore, the hallmark is 375.