If you have ever shopped for gold jewelry or bullion, you have seen the letter “K” next to a number — 24K, 22K, 18K, and so on. That “K” stands for karat, and it tells you how pure the gold is. Understanding karats is the single most useful thing you can learn before buying gold, because purity directly affects both price and durability.
What does karat actually measure?
Karat measures gold purity in parts out of 24. Pure gold is 24 karat, meaning all 24 parts are gold. When gold is mixed with other metals such as copper, silver, or zinc, the karat number drops. So 18K gold is 18 parts gold and 6 parts other metals, which works out to 75% pure.
It is important not to confuse karat (purity) with carat (a unit of weight used for gemstones). They sound identical but measure completely different things.
The common purities
24K (99.9% pure) is the softest and most valuable form of gold. It is popular for bars, coins, and investment, but too soft for everyday jewelry. 22K (about 91.6%) is a classic choice for jewelry in many parts of the world, balancing high gold content with a little extra durability.
21K (about 87.5%) is widely used in the Middle East, while 18K (75%) is the global standard for fine jewelry — durable enough for daily wear while still being unmistakably gold. Lower karats like 14K and 10K contain more alloy, making them harder and more affordable.
How karat affects price
Because price tracks the amount of pure gold, a higher karat costs more per gram. You can estimate the metal value of any item by multiplying the pure gold spot price by the purity fraction. For example, 22K gold is worth roughly 91.6% of the 24K price, gram for gram. Our converter and purity calculator do this math for you instantly using live prices.
Which karat should you choose?
If you are buying purely as an investment, higher purity (24K bars or coins) keeps you closest to the spot price. If you are buying jewelry you intend to wear, 18K or 22K offers a better balance of beauty and durability. There is no single right answer — it depends on whether you prioritize resale value or everyday wearability.
How to read gold hallmarks
Most gold items carry a small stamp, called a hallmark, that indicates their purity. Alongside the familiar karat marks you will often see a three-digit number representing parts per thousand: 999 for 24K, 916 for 22K, 875 for 21K, 750 for 18K, and 585 for 14K. Learning to read these marks lets you confirm what you are buying. If a piece has no hallmark, ask the seller for documentation, and remember that reputable dealers will always be transparent about purity.
Once you know the karat, you can use our purity calculator to estimate the pure gold content and metal value of any item in seconds — a handy check before you buy or sell.