More Than Just a Letter: The Difference Between Carat and Karat

One of the most frequently asked questions I receive is what’s the difference between carat and karat?  These identical sounding words mean very different things and it can be confusing for those who are not used to using them every day.

The key thing to remember is that one is a unit of measurement and the other is a unit of fineness. 

History and Use of Carat and Karat

The word carat has origins in several languages including, Arabic’s qirat, Medieval Latin’s quaratus and Greek’s keration.  Carat is the term used to define a unit of measure for the weight of diamonds and other gemstones.  1 carat equaling 0.2 grams or 200 milligrams (mg) became standardized as the 200 mg metric carat in 1907 and is used around the world today.  Carat is often abbreviated as ct. 

Jewelry pieces featuring multiple stones of the same type, such as a 3 stone diamond engagement ring featuring a 1 carat center stone and 2 0.25 carat diamonds on either side, would have the total amount of carats described as 1.5 carats total weight or abbreviated to 1.5 ctw or cts. t.w.   

The term karat refers to the fineness of gold.  Pure gold is 24 karat and too soft for use in jewelry so it’s alloyed with other metals to be stronger.  This alloy process is how we get different karat gold.  18 karat or 18k gold is 75% pure gold, 14 karat or 14k gold is 58% pure gold and 10 karat or 10k gold is 41% pure gold.  The quality of the metal in your jewelry can be identified via a stamp or engraving the jeweler placed typically near the clasp for bracelets and necklaces, on the inside of ring bands, and on the post back for earrings.*

Which karat of gold is best?

There are several things to consider when selecting the karat of your gold, including lifestyle, sentimental, cultural or religious values, and the overall beauty of the piece.  18k gold is a deeper and richer gold color than lower karat gold and because of its higher purity level it will be more expensive than 14k or 10k gold.  Due to color differences, sometimes a specific karat of gold will look better with your favorite gemstones than another.  My favorite gold is 18k.  I love how it looks with all  kinds of gemstones and 18k looks striking when combined with sterling silver or platinum in mixed metal jewelry designs. 

As with all things, determining what is best varies from person to person, so when selecting a jewelry piece for yourself or as a gift, your favorite jeweler can help you decide on which jewels and karats of gold are best for your unique needs.

*Millesimal Fineness 

Millesimal fineness is another way of denoting metal purity for gold, platinum and silver by a parts per thousand system whereas the karat system is limited to strictly gold. For example, 18k gold is 75% (750 parts per 1000) pure gold and using the millesimal fineness scale would be marked 750. The millesimal fineness scale is predominately used in Europe and the karat system is used in the United States and United Kingdom. The most common millesimal fineness marks for precious metals used in jewelry is listed below.

Platinum 950

18k gold 750

14k gold 585

10k gold 417

Sterling silver 925 or .925