Diamond guides
Diamond Clarity
Clarity describes what is inside a diamond, graded under ten times magnification — which is not how anyone looks at a ring.
The scale
Flawless through Included
The grades run FL and IF, then VVS1 and VVS2, VS1 and VS2, SI1 and SI2, and finally I1, I2 and I3.
What it means for you
Eye-clean is the question that matters
The grade is assigned under magnification. What matters to you is whether a stone is eye-clean — nothing visible unaided. Plenty of VS and many SI1 stones are, at a fraction of the price of flawless.
Position matters as much as grade. An inclusion under the crown, where light enters, shows far more than the same thing near the girdle where a setting may cover it.
One more thing
Colored stones are judged differently
Applying this scale to a colored stone is the most common mistake buyers make. See clarity in colored stones.