Understanding the 4Cs
Updated 10 August 2026 · 4 min read
The 4Cs are the four qualities used to grade a diamond: cut (how well it is shaped to reflect light), colour (how colourless it is), clarity (how free of inclusions it is), and carat (its weight). Cut has the biggest impact on sparkle; carat has the biggest impact on price.
Cut, the most important C
Cut refers to how well a diamond has been shaped and faceted, not its shape (round, oval, etc.). A well-cut stone reflects light back through the top and sparkles; a poorly cut one looks dull even if the other Cs are high. Because cut has the biggest effect on how a diamond actually looks, it is the C worth prioritising.
Colour
Diamond colour is graded from D (completely colourless) down through the alphabet as a faint warmth appears. For most people, a stone in the near-colourless range looks white to the naked eye, especially once set, so you rarely need the very top grade to get a bright, white-looking diamond.
Clarity
Clarity measures tiny natural inclusions. Many inclusions are microscopic and invisible without magnification, so an "eye-clean" stone, one with no inclusions visible to the naked eye, looks flawless in wear without paying for the highest laboratory grade.
Carat
Carat is a measure of weight, not size, though larger carat weights generally look bigger. Price rises steeply with carat, so a small step down in weight, or choosing a shape that looks larger for its weight, like oval or marquise, can stretch the budget without an obvious visual difference.
How the 4Cs apply to lab grown diamonds
Lab grown diamonds are graded on exactly the same 4Cs by the same laboratories (such as IGI), because they are real diamonds. The advantage is value: for the same budget you can usually choose a higher grade across the 4Cs than with a mined diamond, or a larger stone at the same grade.
| C | What it affects | Practical tip |
|---|---|---|
| Cut | Sparkle | Prioritise it, it makes the stone come alive |
| Colour | Whiteness | Near-colourless usually looks white once set |
| Clarity | Flawlessness | Aim for "eye-clean" rather than the top grade |
| Carat | Size / price | Small drops in weight save a lot with little visible change |
Frequently Asked Questions
Which of the 4Cs matters most?
Cut. It has the biggest impact on how much a diamond sparkles, a well-cut stone outshines a larger or higher-colour stone that is poorly cut.
Do lab grown diamonds use the same 4Cs?
Yes, lab grown diamonds are real diamonds and are graded on the same cut, colour, clarity and carat scale by the same independent labs.
What does "eye-clean" mean?
Eye-clean means a diamond has no inclusions visible to the naked eye. It looks flawless in wear without the cost of the very highest clarity grade.
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