The 4Cs — Cut, Colour, Clarity and Carat Weight — are the globally recognized framework created by GIA for communicating diamond quality. Use this guide to understand what each C means and what to look for when comparing diamonds.
How a diamond's proportions and facet arrangement affect brilliance, sparkle and fire.
The degree of colourlessness, commonly graded on the GIA D-to-Z scale.
The relative amount, size and position of inclusions and blemishes.
A measurement of diamond weight. One metric carat equals 200 milligrams.
GIA's 4Cs provide a consistent language for describing and evaluating diamond characteristics. Each C represents a different property of the stone.
Cut refers to the proportions, symmetry and facet arrangement of a diamond. For round brilliant diamonds, GIA uses grades including Excellent, Very Good, Good, Fair and Poor. Cut strongly influences how the diamond handles light and therefore its brilliance, sparkle and fire.
In the GIA D-to-Z system, colour grades describe the degree of colourlessness in a diamond. D is colourless and the scale progresses toward Z, which is light yellow or brown. Colour differences can be subtle but can affect quality and price.
Clarity describes the relative absence of inclusions and blemishes. GIA's clarity scale has 11 grades, ranging from Flawless (FL) to Included (I3). Grading considers factors such as the size, nature, number, position and relief of clarity characteristics visible under 10× magnification.
Carat is the unit used to measure diamond weight. One metric carat equals 200 milligrams. A larger carat weight does not automatically mean a better quality diamond; two diamonds with the same carat weight can differ in cut, colour, clarity and price.
A diamond is more than a single grade. Compare the 4Cs together and use a grading report from a reputable laboratory when applicable.
Look for a credible diamond grading report that records the stone's 4Cs and other relevant characteristics.
Two diamonds of the same carat weight can have different cut, colour, clarity and therefore different appearance and value.
For round brilliant diamonds, cut is an important factor in how effectively the stone returns light.
Clarity grading is based on characteristics assessed under 10× magnification, not simply what you see with the naked eye.
Small colour differences can be difficult for an untrained eye to detect, but they can influence diamond quality and price.
When comparing diamonds, keep the shape, grading basis, and major specifications consistent so the comparison is meaningful.
| 4C | What It Measures | Common Grading / Unit | Why It Matters |
|---|---|---|---|
| Cut | Proportions, symmetry and facet arrangement | Excellent → Poor for applicable GIA cut grading | Strongly influences light return and sparkle |
| Colour | Degree of colourlessness | D → Z | Colour differences can affect appearance and price |
| Clarity | Inclusions and blemishes | FL → I3 | Measures relative clarity characteristics |
| Carat Weight | Diamond weight | Carat (ct) | Helps communicate stone size/weight and can affect rarity and price |
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