A diamond's clarity is determined by how many imperfections, or inclusions, it has. In addition to the number of inclusions, clarity grade is also decided by the size, type, and placement of the inclusions. In general, the fewer inclusions a diamond has, the more brilliance it displays and the more it is valued.

The natural inclusions of a diamond make it very unique – much like a fingerprint, no two diamonds are the same. To determine the clarity of a diamond, it must be examined by a gemologist under 10x magnification. Inclusions include air bubbles, cracks, scratches, pits, and non-diamond minerals that can detract from the pure beauty of a diamond.

Clarity is graded by the number of inclusions and their placement within the diamond. A diamond with only a few hard to see pinpricks located near the edge, where they can be covered by the mounting, has better clarity than a stone with a crack located right under the table (the large top facet of the stone). Cracks from the surface to the interior are especially dangerous because the diamond could break if hit the wrong way. On the other hand, small nicks and chips on the surface are often of little concern because they can be polished away.

The following is the GIA scale, which is commonly used in the United States, along with corresponding definitions for different clarity grades:

	Flawless (FL) Free from all inclusions or blemishes at 10x magnification. Very rare and beautiful.
	Internally Flawless (IF) No inclusions visible at 10x, insignificant surface flaws. Also very rare and beautiful.
	Very, Very Slightly Included (VVS1 & VVS2) Very difficult to see inclusions under 10x magnification. An excellent quality diamond.
	Very Slightly Included (VS1 & VS2) Inclusions are not visible to the unaided eye. Less expensive than the VVS1 and VVS2 grades.
	Slightly Included (S1 & S2) Inclusions are easy to see under 10x magnification. Some inclusions in the SI2 grade may be visible with the unaided eye. A good diamond value.
	Included (I1, I2 & I3) Inclusions are easily visible with the unaided eye. DiamondsRight does not sell included diamonds.