How to Read Gold Karat Marks

The tiny stamps inside rings and on clasps tell you a lot about a piece of gold jewelry, if you know how to read them. This guide explains what karat marks and number marks mean, what plating stamps look like, and what the other symbols you may find are telling you.

What a karat is

Karat is a measure of gold purity, based on 24 parts. Pure gold is 24 karat. A 14 karat piece is 14 parts gold and 10 parts other metals, such as silver, copper, zinc or nickel. Those added metals make the gold harder and change its color.

Karat is different from carat, which is a unit of weight used for gemstones. The two words sound alike, which causes a lot of confusion when people talk about diamond rings.

Common karat stamps

• 24K: Pure or nearly pure gold. Soft, deep yellow, and more common in bullion and some jewelry traditions than in everyday American jewelry.
• 22K: High purity with a rich color, common in jewelry from South Asia and the Middle East.
• 18K: Three-quarters gold. Often used for fine jewelry and better watches.
• 14K: Slightly more than half gold. The most common purity in American jewelry.
• 10K: The lowest purity that can legally be sold as karat gold in the United States. Common in class rings and inexpensive chains.

You may also see 9K on British and older European pieces. You may see the letters KP after a number, such as 14KP, which means "karat plumb," a manufacturer's statement that the gold meets or exceeds that karat.

Number (millesimal) marks

Much of the world marks gold in parts per thousand instead of karats. These are worth memorizing:

• 375 equals 9K
• 417 equals 10K
• 585 equals 14K
• 750 equals 18K
• 916 or 917 equals 22K
• 999 or 999.9 equals 24K (fine gold)

A ring stamped 585 is the same purity as one stamped 14K. The number system is just another way of writing it.

Stamps that mean plated or filled

Some stamps tell you the piece is not solid gold. These are some of the most important to recognize before you buy or sell.

• GF or "Gold Filled": A layer of gold bonded to a base metal core. It wears well but contains only a small amount of gold.
• A fraction plus a karat, such as 1/20 12K or 1/10 14K: Also gold filled; the fraction is the share of the total weight that is gold of that karat.
• RGP: Rolled gold plate, similar to gold filled but with a thinner layer.
• GP, GEP, HGE or HGP: Gold plated, gold electroplated, or heavy gold electroplate. The gold layer is very thin.
• Vermeil: Gold plating over sterling silver.

A stamp like "14K GF" is easy to misread as 14K solid. Always read the whole mark.

Other marks you may find

Next to the karat stamp you may see a maker's mark, which is a logo, initials or name identifying the manufacturer or designer. In the US, a maker's mark is commonly expected alongside a quality mark. A recognized designer or company name can add value beyond the gold itself, so look it up before you sell.

British and some European pieces may carry a full set of hallmarks: a purity mark, an assay office symbol and a date letter. These can tell you where and roughly when a piece was tested. Reference books on hallmarks can help you decode them.

Some pieces also show a number like 925, which means sterling silver, not gold. Two-tone pieces can carry both silver and gold marks.

How to find and read a mark

1. Clean the area gently with a soft cloth so dirt does not hide the stamp.
2. Use a jeweler's loupe or a strong magnifying glass in good light.
3. Check the inside of ring shanks, the tongue or tag near a chain clasp, earring posts and backs, and the bail of a pendant.
4. Write down exactly what you see, including any letters or symbols, and photograph it if you can.

When a mark is missing or unclear

Ring resizing can remove a stamp, and older or handmade pieces were not always marked. A missing mark does not mean a piece is fake, and a clear mark does not guarantee it is real. Counterfeit stamps exist. The only sure answer is a test by a jeweler, gold buyer or assay lab.

Quick checklist

• Use a loupe and good light to find the stamp.
• Match number marks to karats: 417 is 10K, 585 is 14K, 750 is 18K.
• Watch for GF, GP, RGP, HGE and fraction marks, which mean not solid.
• Note any maker's or designer's mark and research it.
• Have unmarked or doubtful pieces tested before you rely on them.