The 4Cs of diamonds

Carat, cut, color and clarity: the shared language every diamond is graded in, and how to read it with confidence.

One yardstick for every diamond.

Introduced by GIA, the 4Cs give every diamond the same set of measures. That means you can compare stones clearly, and know exactly what you are paying for.

Size, measured in weight.

• One carat equals 200 milligrams.
• Price generally rises with weight, and often steps up at milestones such as 1 carat.
• Cut and shape change how large a stone looks, so two diamonds of equal weight can look different in size.

Approximate face-up diameter of a round brilliant, shown to relative scale.

What makes it sparkle.

• Cut is how well a diamond's facets are proportioned and polished to return light.
• For round brilliants, GIA grades cut from Excellent to Poor.
• Other shapes are judged on proportions, polish and symmetry.

Filled grades: the range we set. Every diamond we set is cut to Very Good or Excellent.

How colorless it is.

• White diamonds are graded from D (colorless) to Z.
• The less color, the more light returns, and the rarer the stone.
• Fancy-colored diamonds are graded on hue, tone and saturation. Stronger color generally adds value.

How clean it is.

• Clarity describes the tiny natural marks inside and on a diamond.
• Grades run from Flawless (FL) to Included (I3), assessed at 10× magnification.
• Many marks are only visible under magnification, so a lower grade is not always visible to the eye.

Filled grades: the range we set, Flawless to SI1.

• FL, IF · no inclusions visible at 10×
• VVS1, VVS2 · minute inclusions, very hard to see at 10×
• VS1, VS2 · minor inclusions, seen with effort at 10×
• SI1, SI2 · noticeable at 10×
• I1–I3 · inclusions visible to the naked eye