Diamond size and diamond carat guide

Diamond engagement ring guide


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

Did you know

The word carat derives from the carob tree. Carob seeds, once believed to have a uniform weight, were used for centuries as the standard against which precious gems were weighed.


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’.

Buying loose diamonds for your engagement ring

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, it will add a memorable twist to a story you’ll tell for years to come. 

Did you know

The Cullinan diamond – the largest gem-quality rough diamond ever discovered – weighed a remarkable 3,106.75 carats.

What diamond caratage should I choose?

Consider your partner’s unique style. Do they accessorize striking wardrobe choices with bold statement jewelry? Or, does their minimalist taste suggest a preference for elegant simplicity? This is a ring they will wear and treasure every day for the rest of their life, so ensure that it complements their personality.

If your partner has an active lifestyle, or a job where they work with their hands – for example, as a gardener or a chef – a smaller diamond is a popular, and practical, choice.

If they travel internationally, or work in situations where an obviously large diamond may attract unwanted attention, consider whether a more discreet diamond caratage offers a more desirable option.

Consider the other 3Cs – cut, clarity and color – before making your final decision. All De Beers Forevermark diamonds go beyond the 4Cs to ensure each and every diamond is cut beautifully and has a good standard of clarity.

Diamond engagement ring checklist

Download our handy printable checklist to ensure you have everything you need before you visit your jewelers.

Download now

Beyond the 4Cs

Throughout history, diamonds have dazzled and amazed. At De Beers Forevermark, we individually select diamonds against additional rigid criteria to ensure that only the most beautiful diamonds can become De Beers Forevermark.

Forever Guides

Sometimes a little help along the way is needed. From choosing the right ring size, to the perfect diamond engagement ring, or just simply how to care for your diamond; be inspired.