Carat vs. Karat
When discussing jewelry, precious metals, and gemstones, we discuss both carats and karats, both pronounced “carrot.” Some people use them interchangeably, but this isn’t quite accurate. There are slight differences between the two that can be important to understand. Some places use one spelling more than the other while others may use both. Learning to understand the difference can help provide clarity when reading information about jewelry or precious metals investing. Though a slight difference, this can help you from accidentally making an otherwise-preventable mistake.
Carat refers to the purity of gold or the weight of a diamond on calibrated scales. This is the oldest spelling used for the two, but typically refers to diamonds. The spelling, ‘karat’ arose to differentiate gold from diamonds.
What is a Carat?
The word carat comes from an Ancient Greek word for carob seed. Because carob beans were used to act as very small weights, they were commonly used to weigh gold coins. Because carob seeds varied so little in weight, they were effective in a time when advanced technology didn’t make exact weights possible to track. Nowadays, when we discuss the carat of a diamond, we refer to its weight.
A gold carat refers to the purity of gold rather than its weight. 24-carat gold is what we call pure gold, but it is actually 999/1000 parts gold because it is impossible to achieve a true 100% purity of a metal. So, by purifying gold down to 99.9% gold, we refer to it as pure, which we rate 24-carat.
While desirable for value, 24-carat gold is too soft to be used for jewelry. It must be blended with other metals to create an alloy to be stable and durable enough to create long-lasting jewelry pieces. From there, the ratio of gold to other metals is measured out of 24. 18-carat gold is 18/24 parts pure gold. 9-carat gold is 9/24 parts gold, and so on.
A carat is typically written out in full rather than abbreviated. However, you may sometimes encounter it written as ct., such as a 0.5ct. diamond.
Karat is an alternative spelling for carat to refer specifically to gold. Unlike carat, it cannot be used to refer to diamonds. This allows for the differentiation to be made when discussing the purity of gold to the weight of the gemstones in a piece of jewelry. For example, you can have a ring that is 18-karat gold and a diamond weighing 0.5 carats. While it could be written as an 18-carat gold ring with a 0.5-carat diamond, that can be confusing at a glance. Karats are usually abbreviated with K.
The Bottom Line
Ultimately, when referring to the purity of gold, you can use carat or karat. Some regions will have standard preferences. For example, Australia typically uses carat for both the weight of gemstones and the purity of gold. Just remember that you cannot use karat to refer to precious gemstones. When in doubt, defaulting to the carat spelling is likely to be correct regardless of the context.