The full scale
| Grade | Stands for | What is in there | Clean to the eye? |
|---|---|---|---|
| FL | Flawless | Nothing, inside or out, at 10x | Yes |
| IF | Internally Flawless | Surface marks only | Yes |
| VVS1 | Very Very Slightly Included 1 | Extremely hard to see at 10x | Yes |
| VVS2 | Very Very Slightly Included 2 | Very hard to see at 10x | Yes |
| VS1 | Very Slightly Included 1 | Minor, needs effort at 10x | Yes |
| VS2 | Very Slightly Included 2 | Minor, findable at 10x | Yes |
| SI1 | Slightly Included 1 | Noticeable at 10x | Usually |
| SI2 | Slightly Included 2 | Easy at 10x | Sometimes not |
| I1 | Included 1 | Obvious at 10x | No |
| I2 | Included 2 | Obvious, affects brilliance | No |
| I3 | Included 3 | Heavy, may affect durability | No |
The phrase that matters: at 10x
Every grade on that chart is assigned by a grader looking through a ten power loupe. Nobody wearing a ring is doing that, and nobody looking at your hand across a table is either.
Which means the practical question is not what grade the stone has, but whether anything shows without magnification. From VS2 upward the answer is no. That is the line where money stops buying appearance and starts buying rarity on paper.
Where the inclusion sits beats what grade it is
Two SI1 stones can look completely different. An inclusion directly under the table in the middle of the stone sits in the most visible spot there is. The same inclusion out near the girdle disappears under a prong and nobody will ever see it.
This is why an SI1 you have looked at is a better buy than a VS1 you have not. Ask for the plotted diagram on the certificate, which shows where the inclusions are, and look at the stone.
What the inclusions actually are
Pinpoints are tiny crystals, the most common thing you will see. Clouds are clusters of them, and a dense cloud can make a stone look hazy even at a decent grade, which is worth watching for. Feathers are small fractures and are usually harmless unless large and surface-reaching. Crystals are included minerals, sometimes dark enough to spot by eye at SI2 and below.
Not sure what you are looking at?
Photograph the stone and the app gives you a visual read on the 4Cs, an estimated value range, and what to check next. Free on iOS and Android.
Frequently asked questions
What is the lowest clarity that still looks clean?
What does the number after VS or SI mean?
Is flawless worth paying for?
Do inclusions weaken a diamond?
Worth being clear: everything here, and the app itself, is an educational reference. At-home tests narrow things down, they do not certify a stone. Before you buy, sell or insure anything of real value, get it looked at by a certified gemologist or an independent appraiser.