If you are buying a diamond for the first time, you will quickly encounter the term “the 4Cs”.
The 4Cs are the international standard used to describe and compare diamonds: cut, color, clarity, and carat weight.

They were developed to create a shared language in an industry where diamonds can otherwise be difficult to compare, especially when buying online.

Understanding the 4Cs will help you focus on what actually affects a diamond’s appearance and value, and avoid paying for things that do not matter to you.

1. Cut: how a diamond handles light

Cut is often misunderstood. It does not refer to the diamond’s shape (round, oval, pear).
Cut describes how well the diamond has been proportioned and polished.

A well-cut diamond reflects light back to the eye, creating brightness, fire, and sparkle.
A poorly cut diamond can look dull, even if it has high color and clarity grades.

Cut quality is influenced by:

• Proportions (table size, depth, angles)
• Symmetry
• Polish

Among professionals, cut is widely considered the most important of the 4Cs because it has the greatest impact on how the diamond looks in real life.

For more detail on how cut is evaluated, see the guidelines published by the GIA.

2. Color: how white a diamond appears

image obtained from GIA

Diamond color refers to the absence of color in white diamonds.
The standard color scale runs from D (colorless) to Z (light yellow or brown).

In practice:

• D–F are considered colorless
• G–J are near colorless
• K and below show more visible warmth

Small differences in color grade are often very difficult to see, especially once a diamond is set in jewelry. Lighting, cut quality, and metal choice all affect how color is perceived.

The official color grading scale is explained in detail by GIA here.

3. Clarity: internal characteristics and inclusions

Clarity describes the presence of natural internal features (inclusions) and external features (blemishes).

Clarity grades range from:

• FL (Flawless)
• IF (Internally Flawless)
• VVS, VS, SI
• I (Included)

Most inclusions are microscopic and not visible to the naked eye.
For many buyers, a diamond that is “eye-clean” offers the best balance between appearance and value.

Clarity grading standards are published by both GIA and the IGI. 

4. Carat: weight, not size

Carat refers to the weight of a diamond, not its visual size.
One carat equals 0.20 grams.

Two diamonds with the same carat weight can look very different in size depending on:

• Shape
• Cut proportions
• Depth

Carat weight has a strong influence on price, especially at popular “magic sizes” such as 1.00 ct or 2.00 ct. In many cases, choosing a diamond just below these thresholds offers better value without a visible difference.

IGI explains carat weight and measurement here

How the 4Cs work together

No single C tells the full story.
A diamond with excellent cut but slightly lower color can look more beautiful than a higher color diamond with poor proportions.

The best approach is to balance the 4Cs based on your priorities, and always review:

• The full grading report
• Proportions and measurements
• Videos or images of the actual diamond

A note on certificates

The 4Cs are recorded on independent grading reports issued by gemological laboratories such as GIA and IGI.
A certificate does not make a diamond better, but it provides a standardized way to compare stones.

If you would like to understand how different laboratories compare, see our guide:
IGI vs GIA diamond certificates: what EU buyers should know

In summary

• Cut affects sparkle more than anything else
• Color differences are often subtle
• Many inclusions are invisible without magnification
• Carat is weight, not visual size

Understanding the 4Cs allows you to buy with confidence and focus on what truly matters to you.

If you need help interpreting a grading report or comparing diamonds, our concierge team is happy to guide you.

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Frequently asked Questions: 

1. What are the 4Cs of diamonds?
The 4Cs are cut, color, clarity, and carat weight. They are the international standard used to describe and compare diamonds.

2. Which of the 4Cs matters most?
Cut is widely considered the most important of the 4Cs because it has the greatest impact on how a diamond looks, including its brightness and sparkle.

3. Is carat the same as size?
No. Carat refers to a diamond’s weight, not its visual size. Two diamonds with the same carat weight can look different depending on cut and proportions.