Understanding the 4Cs of Diamond Grading

Understanding the 4Cs of Diamond Grading

A lot of people know that when shopping for diamonds you should ask about Carat, Colour and Clarity but do you know what they mean? Read on for our simple guide to the 4 Cs of Diamond Grading…


Most people know that diamonds are measured in carats (ct), but ‘carat’ is often mistaken for a unit of size. Carat is actually a measurement of weight, with one carat equalling 0.2g – it may not sound like much, but it’s big numbers in jewellery terms!

Carat weight is roughly related to size but this can depend on the shape and proportions of a diamond. A 1ct round diamond will be a different size to a 1ct square diamond.

The total weight of all the diamonds in a piece of jewellery is the Carat Weight of an item – of course if that is a solitaire diamond, then that stone alone makes up the whole carat weight! For example a pair of diamond earrings might have each stone weighing a quarter carat – making the whole pair a half carat. Or a cluster of diamonds in a ring might weigh a half carat in total.

Big or small, it doesn’t matter how you mix and match your diamonds – the total weight will be the same, but the look of the jewellery might be very different.


We use the word ‘cut’ to refer to the shape of a diamond – you might have heard of shapes such as brilliant cut, marquise cut, princess cut. But when we talk about cut as one of the ‘4 Cs’ we actually mean the quality of the cut – not just it’s shape!

Diamonds are measured on their symmetry, the proportion of the stone and the angles of the facets, and the quality of polish. A well-cut diamond bounces light around to sparkle no matter what direction it is viewed from. A diamond that has been cut too deep, or too shallow, appears dull by comparison.

You will usually find that older diamonds are cut to different proportions; diamond cutting technology and tastes have changed over the years. Just because a diamond isn’t perfectly symmetrical, doesn’t mean it can’t be beautiful. Remember, a diamond should be judged on its overall appearance, not by one of the 4 Cs in isolation!


You might think of diamonds as being colourless, but many diamonds actually have a slight yellow tint to them! This is completely natural and often undetectable.

A diamond’s colour grade is an assessment of how colourless a diamond is – with the top rank being a completely colourless diamond. Colour grades are ranked alphabetically starting from D, although differences between individual grades can be very subtle. If you compare diamonds that are a few colour grades apart – for example, an E grade and an I grade – you will see which one is brighter.

Diamond colour isn’t the whole story. A good colour diamond still needs a good cut and reasonable clarity to look its best! As always, we recommend inspecting a stone based on its overall appearance rather than judging it by a single characteristic.


Clarity refers to the number of inclusions in a diamond. Inclusions are the natural marks left behind from when the diamond crystal originally grew, and can be more or less noticeable depending on their size and position within the cut diamond.

Most inclusions are too small to be seen with the naked eye. Jewellers use 10x magnification to inspect diamonds for inclusions. The clarity grade is based on how many and how visible the inclusions are.

The highest clarity grade is an IF – internally flawless diamond. This is very rare, so you are much more likely to find diamonds that are VVS (very very slightly), VS (very slightly) included, or SI (slightly included). Diamonds which have inclusions visible to the naked eye are graded I (included).

Diamonds with fewer inclusions are more highly prized because they reflect light better. However a diamond also needs a good cut and reasonable colour to look its best. An I grade clarity diamond can still be a beautiful stone!

Diamond rings

That concludes our summary of the 4Cs of diamond grading. Hopefully now you know a little more about what to look for when shopping for an ideal diamond.

Feel like looking at some diamonds now? Shop our range of diamond-set jewellery here.

Alternatively, read about the 5th C – Diamond Certification – why not all diamonds needs certificates, but why certificates are becoming more common.