The four Cs of diamonds

The four Cs are color, clarity, cut and carat weight: four scales that give diamonds a shared language. These pages explain what each C measures, its scale and how a lab grades it. In our 3D Gemstone Simulator and Cut Grading Tool, you change one C at a time and see how much it changes the look of a stone.

New here? Start with Carat weight vs size: why a 2 ct diamond isn't twice as big.

1. 1 · Article

   The 4 Cs of diamonds explained: carat, color, clarity and cut

   The four scales, what each one measures, how a lab grades it, and which C changes the look of a stone most.

2. 1 min 28 s

   2 · Animated explainer

   Carat weight vs size: why a 2 ct diamond isn't twice as big

   Why double the carat weight is only 26% wider, with a T73 size chart in mm from 0.25 to 5 ct.

3. 3 · Article

   The diamond color scale, D to Z: where you first see a tint

   What each range from D to Z looks like, how a lab grades color, and why warm light hides the step from D to H.

4. 4 · Article

   Fancy color diamonds and fluorescence: beyond the Z grade

   What fluorescence is, how often it shows and what it does to the look, plus how fancy color grades work past Z.

5. 5 · Article

   The diamond clarity scale explained, from FL to I3

   The 11 clarity grades from FL to I3, what decides each grade, and where inclusions start to show without magnification.

6. 10 s

   6 · Video

   Diamond cut grade: Excellent vs Poor, side by side

   Excellent and Poor side by side: cut vs shape, the light map, leakage at each grade and the shrinking diamond.

7. 10 s

   7 · Video

   How a diamond cut grade is set: proportions, polish and symmetry

   The seven components of a cut grade, why the weakest one wins, and how to take a Poor stone to Excellent.

8. 8 · Article

   Putting the 4 Cs together: which C to spend on

   Which C to spend on: a D Flawless Poor beside an H SI1 Excellent, and bigger vs better cut.

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