Carat vs Karat – What is the Difference?

Have you ever wondered what 24k gold actually meant? Or what the difference between carat and karat is? In the jewelry world, there is a big difference between the two, and there is a long history behind the carat and karat and how it has come to be.

Carat vs Karat

A carat is a measurement used to weigh precious stones, while karat is used to measure the purity of gold. In the diamond business, you can not use the term carat and karat interchangeably. But, with gold, you can use either term and technically be correct. The reason is that the term carat for jewels was standardized in 1907, while the term karat came around in the 16th century. (1)

History of the Karat

In the Greco-Roman times, the carat was a measurement of weight used throughout the land. The carat was the seed of a carob tree. These seeds had a very uniform size and shape and were used all over as a standard of weight. Thought, it did not come to be the standard for the purity of gold until much later.
We come to use 24k gold as a measurement for the pure gold because of Emporer Constantine I of Roman.(2) He created a new money system that included the use of the silver solidus. This coin was 1/72 of a libra or Roman pound. The libra was used to measure out gold by weight. The libra just so happened to weigh the same amount as 24 siliqua (the solidus was measured at 1/24th of a siliqua.) Siliqua is the measured weight of the carob seed. So the carat (and later changed to karat) became a standard measurement for gold.


This origin is why technically both spellings for carat and karat are correct for gold. The original spelling in the Roman language was carat. But, the Germans changed it to karat in the 17th century when they came up with a new coin called the mark. The mark was 90% pure gold and was deemed the standard for 24k gold. The measurement stuck and is now used all around the world.

History of the Carat

In the 1900s people tried to standardize the system for weighing and measuring precious jewels and gems. The carat was already being used as a standard of purity for gold. It had a history of being a standard for weight in most of the Middle East and Europe. So, in 1907 the Fourth General Conference on Weights and Measurements voted and agreed to extend it’s use to the diamond as well.

Weights of the Karat And Carat

Gold is a soft metal that can not be used alone. If a piece of jewelry were made from 100% gold, it would be bent, scratched, and deformed after one use. That is why, in old western movies, men bent the gold coins with their teeth. If it bent, it was real. To strengthen gold suitable for wearing, it has to be mixed with other alloy metals. The most common alloy mixed with gold is copper. With 24k being pure gold, we use that as a way of figuring out how many parts gold and copper there are. So if you have a ring that is 18k gold, that means that 18 parts of the ring are pure gold. And, six parts are made from copper alloys. Likewise, 15K gold is 15 parts gold and nine parts mixed alloys. Etc. Etc.

Measuring a carat is a little more straightforward in terms of actual weights. The Conference on Weights and Measurements designated that one carat would be equal to 0.2 grams or 200 milligrams. When measuring the weight of a diamond, all you need to do is weigh the diamond and convert. So a diamond that weighs 800 milligrams or 0.8 grams would be divided by 200 milligrams or 0.2 grams to equal 4 carats.

So now you know what it means to have a 24k gold ring with a 2-carat diamond!

The history and usage of precious stones and metals are very rich. Gold will always be an essential standard for the world, as well as many valuable gems. Now you can confidently use the terms karat and carat retrospectively and know the worth of your valuables.

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