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What's the Difference Between Carats and Karats?

What's the Difference Between Carats and Karats?

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What's the Difference Between Carats and Karats?

If you're buying jewelry or gold you might be seeing two words that are very similar; carats and karats. Though they sound the same, and can both be used to describe jewelry, the truth is that they measure very different things. Here's a quick guide to understanding the difference between carats and karats: 

Carats Measure the Size of a Gem

A Carat is a word that you will run into when buying or selling gemstones or diamonds. The carat is a measurement that defines the overall mass of the stone. A 1-carat diamond equals 200 milligrams or 1/5th of a gram. A flawless diamond that has at least 100 carats could be called a paragon. The largest uncut diamond in terms of carats is one that comes from Brazil called Sergio. This is by far one of the largest rough diamonds ever found to date. It weighed in at over 3,167 carats and was actually found above ground. Sergio was sold originally for only $16,000 in the 1800's. Today it would probably be sold for $16 million dollars!

Before 1907, each country had their own measurement of measurements for what equaled 1 carat. After 1907, a standard system was put into place at the Fourth General Conference on Weights and Measures which defined 1 carat as 200 mg, no matter which country you're in.

There is, however, one aspect that can still make carats confusing to measure across borders. Although in the US we use "carat" to refer to diamonds and "karat" to measure the quality of gold, many other countries use the opposing spelling variations.

Karats Measure the Purity of Gold

When describing the quality of gold, the proper spelling is "karats". Since gold is often smelted with other metals, "karats" are a measurement of the purity of the material, rather than the sheer size. Karats are calculated by multiplying the mass of the gold by 24 then dividing it by the total mass of the coin. 

These calculations take time and knowledge. This also means that when you're selling gold you need to find a respected professional to do the evaluation for you. They will have a better understanding of how the process and calculations work and can give you a better evaluation.

Below, you can see some of the common purities for gold products, like coins:

  • 99.90% = 24 karat 
  • 91.60% = 22 karat 
  • 83.30% = 20 karat
  • 75.00% = 18 karat
  • 62.50% = 15 karat
  • 58.50% = 14 karat
  • 41.70% = 10 karat
  • 37.50% = 9 karat
  • 33.30% = 8 karat

According to Perth Mint, the purest and most expensive gold coin that was ever produced was by Perth Mint in 1957. This gold coin had a purity of 99.9999%.


If you are interested in selling your used jewelry or you have questions about the process, visit Ralph Mueller & Associates or call us at 480.949.9229.