When buying a diamond engagement ring, the size of the diamond is often the first thing that comes to mind. As a precious symbol of your future together, it’s important that you are happy with your purchase. Having an understanding of how sizing works will offer valuable insights as you make your decision. The term ‘carat’ (commonly abbreviated to just ‘ct’) refers to the weight of a diamond, although it is often (incorrectly) used to describe the size of a diamond.

The definition of a carat has changed over time, but since 1913 the international standard has been 200 milligrams or one-fifth of a gram.

Diamonds can range in weight from a fraction of a carat to several carats. Carats are divided into points where one carat equals 100 points, for example:

  • ½ carat diamond – 50 point or 0.50 carat diamond
  • ¼ carat diamond – 25 point or 0.25 carat diamond


Given the rarity of large diamonds, their price will increase with caratage. You will find, therefore, that a single 2-carat diamond will cost significantly more than two 1 carat diamonds.

It is important to note that the appearance of a diamond does not grow in direct proportion to its carat weight. For example, the size of a 2-carat diamond will not be twice that of a 1-carat diamond.

When there is more than one diamond in an engagement ring, such as in a diamond pavé band or a three-stone ring, the diamonds are weighed together, rather than individually, resulting in ‘total carat weight’.


The diamond you choose is the ultimate symbol of your eternal love and the lifelong promise you are about to embark on, so why not make it the centerpiece of your proposal? Having selected and purchased an exquisite loose diamond to present in that one-off moment, you can choose the ring, metal and setting later – as a couple – and together create a truly personal, unique diamond engagement ring to treasure forever. Not only is this the perfect way to involve your partner, but it will also add a memorable twist to a story you’ll tell for years to come.