Knowing Your Karats

Unlock the secrets behind gold jewelry karat weights. From 24-karat gold jewelry to 9-karat gold styles, find out why weighing more can sometimes be a good thing.
Jewelers throughout the ages have selected gold as their precious metal of choice because of its softness, natural beauty, resistance to erosion or tarnish, and ease of workmanship.
Gold is so soft and malleable that it can be melted and shaped to create virtually any design. But this softness also makes pure gold less than desirable for jewelry usage - which is why it is usually alloyed with other metals such as copper or silver to make it stronger and more durable.
The gold content in a particular alloy is expressed in karats (abbreviated as K or KT). Generally, the higher the percentage of gold content, the softer (and yellower) the piece. The karat weight system used for white gold is the same as that used for yellow gold (white gold is mixed with different alloys to give it a white color).
Here are some common gold karatages (karat weights) and the corresponding percentages of actual gold:

24K represents pure gold (100%) and is rarely used in jewelry.
21K is 21/24ths gold content, or 87.5% gold. Jewelry of this karatage or higher is rare in the United States, although it is far more common in parts of Europe, the Middle East and Southeast Asia.
18K is 18/24ths gold content, or 75% gold. This is a popular karatage for higher end jewelry in the United States, Europe and other regions, and its usage is expanding in North America.
14K is 14/24ths gold content, or roughly 58.5% gold. This is by far the most commonly used karatage in the United States (and perhaps the world) and provides a nice balance between gold content, hardness/durability and affordability.
10K is 10/24ths gold content, or 41.7% gold. This is an increasingly popular karatage sold by many U.S. mall jewelry chains, department stores, discount stores and other mass market venues because it offers budget-conscious consumers precious metal jewelry at more affordable prices than the standard 14K. It is also the lowest gold content that can be legally marked or sold as gold jewelry in the United States. Often used in rings because they tend to be worn every day and experience many knocks and thus require an exceptionally strong alloy.
9K is 9/24ths gold content, or 37.5% gold. This is a popular karatage sold by mass marketers in England and other regions, although it cannot be marked or sold as gold jewelry in the United States.
Sometimes, gold of a lower karat weight is plated in higher-karat gold to enhance its color. This is perfectly acceptable as long as the jeweler discloses this fact and you pay a fair price. Keep in mind that gold plating will wear off over time and your jewelry may need to be re-plated.
To determine the karat weight of a particular piece of jewelry, look for the quality mark. Generally, pieces will either bear the stamp of their karatage based on the U.S. or European system. The U.S. system uses karat designations (24K, 18K, 14K, 10K, etc.) Europe uses number designations which correspond to the percentage of gold content. For instance, 10K is marked "417" for 41.7% gold; 14K is marked "585" for 58.5% gold; 18K is marked "750" for 75% gold, etc.