If all that glitters isn’t gold and diamonds are a girl’s best friend, then what can you say about a 24-karat gold diamond ring? Some might WONDER how many carats the diamond is. Others know it’s probably very valuable, but may be a bit confused by the carats and the karats.

So what does all this talk about carats and karats mean when it comes to gemstones and gold? Does it have anything to do with those tasty orange vegetables that grow in the ground?

Nope! Carats and karats are completely unrelated to carrots. And although they can both be used to describe different types of jewelry, carats and karats measure completely different things.

A carat is a unit of weight. It’s used to describe diamonds and other precious gemstones, such as pearls. One carat is equal to 200 milligrams, which is the same as 0.2 grams. A two-carat diamond would weigh 400 milligrams (0.4 grams).

A karat, on the other hand, is a measure of purity when referring to gold. You may have seen different types of jewelry referred to as 14-karat gold or 18-karat gold. What does that mean and what’s the highest karat gold that exists?

Pure gold is known as 24-karat gold. Gold is a fairly soft metal, though, so it’s not often used to make jewelry. Jewelry made of pure gold can be easily bent and scratched.

Instead, gold is often mixed with other metals, such as copper or silver, to form an alloy that can be used to make jewelry. A karat is equal to 1/24 pure gold, so an 18-karat gold ring would be made with 18 parts gold and 6 parts of another metal.

The amount of gold in jewelry affects its value greatly. For example, 10-karat gold jewelry is less than half gold. On the other hand, 18-karat gold is 75% gold. The purest gold jewelry commonly available is 18-karat gold, and it’s usually much more expensive than lower-karat varieties.

So how did such a measurement of purity come about? Over 1,000 years ago, a German gold coin called a mark was very common. It happened to weigh 24 carats (4.8 grams) and was pure gold. People decided to describe the purity of the gold in the coin based upon its weight in carats and over time changed the “c” in “carat” to a “k” to distinguish the two different measurements.

In the United States, the Federal Trade Commission (FTC) sets the rules for marking jewelry with a karat value. Under FTC regulations, pieces of jewelry that are 10-karat or greater should be stamped with either a “K” or “Kt.”