Carat vs Karat: What’s The Difference And Why Does It Matter?


In a layman’s world, there really is no difference between a Carat and Karat. If they sound the same, they probably are or so you would think.

This is where most get it wrong. In the world of jewelry, the two are not interchangeable. In fact, they serve completely different purposes.

Let’s step out of our world and into the realm of a jewelry expert to gain an understanding of the differences between a Carat and Karat.

At A Glance

Karat and Carat might sound the same, however they are different concepts and serve two distinct purposes.

A karat is a unit of measurement, used to identify the purity of gold.

A carat is a scientific unit of mass, used to determine the weight of gemstones and pearls.

We go over each and what they stand for, how they are used today and where they had come from.

Read this article and become an expert on the differences and similarities between the two.

What in the world is a Karat?

The Karat is a measurement unit, used to identify the purity of gold. It is a standardized measurement for gold alloy composites, in parts fine per 24 parts whole.

Meaning that 24 out of 24 parts of a composite object is made of pure gold. If pure gold is 24-karat, 18k would mean that the gold object is made of 18 pure gold parts out of 24 with 6 parts of a selected alloy composite.

In most cases, when looking for a jewelry piece or checking out tags – the Karat will be abbreviated in the form of K or k.

What is the point of mixing gold?

Pure gold in nature is extremely malleable and soft, which means it cannot be used in daily jewelry pieces or items that require extra durability.

When it comes to jewelry, the last thing you want to happen is for somebody to step on a ring and turn it into a coin.

In order to fix this, refiners mix pure gold with a variety of alloy composites, depending on the desired outcome.

By doing so, they decrease the price while increasing durability and stress-resistance at the cost of losing the original color tint and flexibility.

What about a Carat?

A carat is a scientific unit of mass, which is used to determine the weight of pearls, gemstones or exotic stones.

A carat is equal to 0.2 grams or 200 milligrams, but can often be presented in the format of a troy ounce, which would make it 0.000643 t/oz.

By knowing the weight, we can determine that an 18-carat diamond would be of a 3.6-gram weight. However, this is only an approximation, as most stones have a different density, so one stone of the same weight can be of different shape and size when compared to the other.

For smaller stones, a Carat is often divided into 100 points of weight placement, making each point equal to 2 milligrams of stone weight.

As you would expect a Karat to be abbreviated with a K or k, the carat can be seen in the form of CT or c.

Where do Karat and Carat come from?

The two terms are traced back to ancient times of the Roman Empire. From history, we know that carat is of Greek descent and was used to identify “carob seeds”.

The seeds were used to balance and measure the weight of small objects on a market scale. The size and shape of the carob seeds differ greatly, therefore they did not have the assured reliance, as a diamond carat may have. To measure diamonds, the carat came into play at the turn of the 16th century.

However, the measurement of a carat varied greatly from country to country, until the unit had stopped at the 200-milligram metric carat, which is now globally recognized as the standard.

In England, a carat was divisible into four separate grains, and a single grain could be divided into four quarts.

The reason why people often misinterpret Karat and Carat is that the former had originated from the latter. Karat was an interchangeable variant of Carat.

The fruit of a carob tree was most likely not used to measure gold, as far as we know – however, the closest link between the Karat and where it came from can be traced back to the rule of Roman Emperor Constantine I.

During his command, he established the foundries to mint a new gold coin, solidus, that would be measured in a mass of 24 siliquae or 1/72 of a libra. The siliquae (small silver coin) would represent the proportion of 1/1728 from a pound.

Following the pattern of scale, this number can be brought down to the 24 parts for a karat, which is believed to be the origin of the term itself.

carat weight differences across the world -
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What is fineness? Why is it important?

In the world of luxury, the difference between a bad product and a good one is paramount. To determine the quality of a precious metal object, such as a coin, jewelry piece or bar – a scaling system is used.

Fineness is a measured representation of fine metal weight, in proportion to the entire weight with all of the alloy composites and impurities.

In the process of object synthesis, alloy composites are added to improve the durability and hardness of the item itself. By doing so, one can notice significant alterations in color, decreased cost per weight measurement and/or lower cost for purity maintenance and refinement.

For example, silver is made with copper, in order to make the end product more durable for the production of coins, jewelry, and kitchenware.

Silver coins in the past contained a ratio of 10% copper and 90% silver, by the proportion of mass. Sterling silver consists of a negligible amount of various metals and a majority portion of 92.5% silver.

Fineness is expressed through multiple methods, but the most common are karats (which we have reviewed earlier) for gold and millesimal fineness in a format of parts per 1,000.

Establishing Fineness

There is a myriad of ways used to inspect and determine the authenticity of metal, but in reality, only two options are reasonably accurate and widespread throughout the expert communities:

  1. X-Ray Fluorescence (XRF). It only measures the external layers of the metal and can be tricked by a thick composite plate to cover the internal less-valuable material.
  2. Metal Assay is a process, originating from the experiments of Alchemists. Unfortunately, this method requires complete destruction of the metal structure.

These methods present a list of problems that can at the least be concerning. It is not uncommon for a metal refiner or vendor to produce metal objects or bars that are of lesser purity, yet being evaluated and marked at a higher purity.

By doing so, the refiner would be creating an additional flow of insurmountable income that is difficult to trace.

However, in the US – there is a system in place that allows for a very small degree of variability in fineness, in order to prevent scams of large proportion.

A deeper overview of millesimal fineness

As we have determined the use efficacy of millesimal fineness, as a system for determining the purity of various precious metals, on parts per 1000. We can finally take a closer look at what it really is.

In simple terms, an alloy of 75% gold would be stamped with a purity of 750.

However, in the United States, 75% of gold would be denoted, as an 18 karat. This is to be expected, as the decimal system is not as popular in the US, as it is in Europe.

Millesimal fineness is almost always rounded to a number of three figures, especially in cases of using it as a hallmark.

Here are some examples:

For Silver

A silver item with a fineness rating of 925 is considered a First Law Silver, also known as Sterling Silver. In times of the Spanish conquest, it would be referred to as “Plata de Primera ley”.

For Gold

A gold object with a fineness rating of 916, equaling to 22 karats – is, in fact, the most popular of gold ratings. It is most often used in the first renditions of an American Eagle denomination from the 19th century. However, it is still used in the newer gold eagles and British Sovereigns.

For Platinum

A platinum item with a fineness rating of 950 is considered to be the most common and can be found at any jewelry vendor.

silver vs gold common millesimal finenesses -
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What is fine weight?

When using the fineness scale, one can come across the term of fine weight. If an alloy composite metal has a precious metal component, the portion of the precious material is referred to as the fine weight.

For example, a single troy ounce of 14 karat gold (which is 58.3% gold) can also be established, as having a fine weight of 0.58 troy ounces. Here are some additional examples of karat/percentage ratios:

  • 75% gold = 18k
  • 91.6% gold = 22k
  • 95.83% gold = 23k
  • 99.95% gold = 24k

In Summary

Despite the two terms sounding the same to the ear, they serve completely different purposes.

A karat is a measurement unit, used to identify the purity of gold. It is a standardized measurement for gold alloy composites, in parts fine per 24 parts whole.

A carat is a scientific unit of mass, which is used to determine the weight of pearls, gemstones or exotic stones. A carat is equal to 0.2 grams or 200 milligrams, but can often be presented in the format of a troy ounce, which would make it 0.000643 t/oz.

If you are considering the idea of jewelry purchase, you might as well be ready to make an educated decision. Now you know everything you need to know about a carat and a karat.