What is the difference between 1 Karat and 1 Carat?

When you visit your jewelers, you must have heard them describing the gold jewelry in carat and karat. But did you know that these can be used interchangeably only for GOLD? For precious gemstones as diamonds; only carats are used. Now you might be wondering what the difference between these two is. Let’s wrap our heads around the difference between karat and carat. 

The etymology of the Word

The word carat has been derived from the Greek word, meaning carob tree. In the fifteenth century, people used seeds of the carob tree as a standard to weigh their gemstones. The weight of a carob seed is equivalent to the weight of the smallest gemstone. 

Stones weighing equal to the one seed of the carob tree were termed as carat,” Merriam Webster Dictionary. 

Different instruments and units have been devised for the measurements of the precious metal and gemstones. The legal use of the carat as a standard for gemstones started in 1907 when the 4th General Conference on Weights and Measures introduced Metric Carat for weighing gemstones. The unit was then standardized as 200 milligrams metric carat. This is used worldwide today.


Photo by Morgan McDonald on Unsplash

But how come the term carat came into use for the purity of gold? Over ten decades ago, the German gold coin called mark was widely used. It weighed 24 carats or 4.8 grams. That led people to describe the purity of gold in a coin based on its weight in carat. With time, the use of carat for gold became obsolete and karat was introduced to differentiate between the two different items. It is calculated as; 24 times the pure mass upon total mass. 

K= 24 * M (gold)M (total mass)

Karat and Carat

When someone is talking about a 24 karat diamond ring they’re going to buy for their fiancé or loved ones; you might think would it be as valuable as their love? How’d you evaluate such a valuable jewel? By the purity of its gold or the quality of diamond! To be able to assess the value of the jewel, you must know what a karat or carat represents.

The term karat is used to express the proportion of gold in alloy whereas carat is the unit for the weight and size of the gemstones.

The karat indicates the proportion of gold in an alloy of 24 parts such as 14k gold is 14 parts gold by 24 parts. It is reflective of the purity of gold. One carat is equal to 0.2grams or 200 milligrams. 

In abbreviations, a karat is denoted as uppercase K like 14K or 24K whereas the carat is written as ct. 

Karat; the purity of gold

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We just said that karat is not the unit for a weighed quantity. Rather it is reflective of the purity of gold. 24-karat gold is termed Pure Gold. It is a soft metal that doesn’t fit jewelry making as it is malleable and gets scratched easily. 

Therefore gold is alloyed with other metals such as nickel, copper, silver, etc. These metals increase the metallic strength of gold, impart Luster, and help change its color. Only after alloying it can be used in jewelry making. But alloying gold with metals has its drawbacks. These metals undergo oxidation and cause corrosion. This leaves a black smudge on the jewelry as well as on your skin.

Since a karat equals 1/24 of gold, 18 karat gold ring is made with 18 parts gold. Renaming 6 parts are of alloyed metal either copper or nickel. You can convert the proportions to the percentages for an easy understanding. A karat is can be defined as 4.1667 percent pure gold. 24 karat gold is 100% pure gold but 18K gold is 75% pure gold and 25% metal alloys. 

You can use a mixed proportion of the alloys for the same karat value as per your desired color. 

  • 75% gold mixed with20% fine silver and 5% copper gives yellow gold.
  • 75% gold mixed with20% copper and 5% fine silver gives rose gold.
  • 75% gold mixed with 25% palladium or platinum gives white gold.

Thus, the higher the carat weight, the purer and softer it is. And it is more valuable than low karat jewelry. (Did you notice I used carats for gold?) The karat cannot be substituted for the carat of the gemstones. However, a carat can be used as a variant to define the purity of gold. 

Carat; the weight of the diamond

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When dealing with diamonds, you must have heard of the 4Cs. These are defined as Cut, Clarity, Color, and Carat. Accurate carat weight is imperative when comparing gemstones or setting the price. A carat is equal to one-fifth of a gram. It can be put simply as 0.2 gram or 200 milligrams. Likewise, one gram of diamond equals five carats. That’s the typical range; between 0.2 carats and 5 carats. A “paragon” diamond is a flawless diamond that weighs about 100 carats. A carat is divided into 100 points. And a half-carat diamond is called a 50 pointer. 

Two diamonds that may look similar in size can vary in their carat weight. This is due to the cutting of the gemstone. It is recommended to buy a smaller diamond with the proper cut as it gives excellent sparkle, fire, brilliance, and scintillation. Also, two gemstones that have similar carat weight can vary in their size. This is because different gemstones have different densities. 

The diamond’s carat weight is different from the total carat weight of the ring. The latter is the sum of the weight of all the diamonds in the ring. 18k gold ring band with a center diamond is preferred for jewelry making to ensure the perfect setting. The karat weight of the metal ring band, as well as other Cs of the diamond, is also important factors to be considered.


 So far the numerical difference between the karat and carat has been cleared. All you have to do is mention the following three points if someone asks you about the difference between karat and a carat. 

  • A carat is a unit of weight for the gemstones as diamonds while karat is the measure of the purity or fineness of gold.
  • A carat is equal to 100 points or 1-fifth of the gram or 0.2 grams in weight whereas a karat is measured on a 1-24 parts scale.
  • The abbreviation for carat is “ct” and for the karat is “K” or “k”.in

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