As if buying a diamond ring isn’t stressful enough, it can be a complicated process. Many of our customers ask ‘What is a carat’ or ‘What is a diamond carat?’. The team here at Lance James the Jewellers are here to help.

One of the most common confusions is about “carats”. You keep hearing the word bandied around but jewellers often forget to explain exactly what the term means.

Your ring is made up of two things: metal (gold, platinum etc) and a stone (diamond or gemstone). Simple so far, right?

However, the term carat is used to describe both parts of the ring but they mean different things.


In terms of metal, carat refers to the purity of the metal. Only used to describe gold, you will most often hear of 9ct and 18ct.

We do not use pure gold to make a ring because it is too soft. By mixing it with other metals (commonly known as an alloy), we can create a more hard wearing metal. Carat indicates how much gold there is in the mix, that is how pure it is.

18ct means that the metal is 75% gold; 9ct metal is 37.5% gold. There are other grades of gold, but these are the most common in the UK.


When talking about diamonds, carat is a measurement of weight. It is not the physical dimension of the stone but how much it weighs. Each carat is split into 100 points, so jewellers may refer to ‘half carat’ or ‘50pts’ – these will be the same size stone.

One last thing to remember, carat does not mean it is a diamond!

This measurement of weight is also used for other gemstones. Other precious and semi precious stones and even lab-created ‘diamonds’ like moissanite will be described using carats.

Don’t assume a 1ct ring is a natural diamond. Make sure you read the small print.

Hope this has help to make things clearer. The team at Lance James are always happy to help, so don’t hesitate to pop into store and ask. You can also call us on 01245 523755.