Diamond Clarity Guide, FL Through I3 With Real Inventory Data

The clarity scale runs eleven grades from FL to I3, and for most buyers shopping rounds under 1.5 carats, eight of them are irrelevant. That's not a criticism of the GIA system. It's a statement about optics: the human eye stops detecting inclusions somewhere around VS2, and the market doesn't always price that gap honestly.

If you're newer to the 4Cs and want the broader framework before going deep on any single factor, our diamond buying guide covers how clarity interacts with cut, colour, and carat weight and why it's rarely the factor that deserves the most of your budget. This post assumes you have that context and want the grade detail.

The grade reference table

Every GIA clarity grade corresponds to a threshold of visibility under 10x magnification. The key question isn't what the grader sees at 10x. It's whether those inclusions survive the journey from the loupe to the naked eye.

Grade	Under 10x loupe	Naked eye	Eye-clean rate
FL	Nothing at all	Nothing	100%
IF	Minor surface blemishes only	Nothing	100%
VVS1	Inclusions barely visible even to trained grader	Nothing	~100%
VVS2	Inclusions very difficult to locate	Nothing	~100%
VS1	Inclusions difficult to see at 10x	Nothing	~99%
VS2	Inclusions minor, fairly easy at 10x	Nothing	~99%
SI1	Inclusions noticeable at 10x	Sometimes visible	~65%
SI2	Inclusions easily seen at 10x	Often visible	~25%
I1	Inclusions obvious, may affect brilliance	Visible	Uncommon
I2	Inclusions very obvious, affect brilliance	Clearly visible	Rare
I3	Inclusions prominent, may affect durability	Obvious	None

FL and IF are functionally identical to anyone without a grading loupe. The IF grade simply means GIA found a minor surface blemish, something that could theoretically be polished away. In a setting, under any normal lighting condition, they look the same. The premium IF commands over VS1 is largely about psychology and collector preference, not visual performance.

Where the value sits

The buyer recommendation table below covers the most common purchasing scenarios. Step cuts follow different logic, addressed below.

Buyer scenario	Recommended minimum	Why
Round brilliant under 1.5ct	VS2	Eye-clean rate ~99%; saving over VS1 is real money for no visible gain
Round brilliant 1.5ct and above	VS1	Larger table amplifies central inclusions
Emerald, Asscher, baguette	VS1	Parallel facets don't scatter light; inclusions read directly
Oval, pear, marquise, cushion	VS2	Brilliant faceting masks inclusions well
Budget-conscious rounds with careful selection	SI1	65% eye-clean rate; requires stone by stone assessment

VS2 is the sweet spot for rounds under 1.5 carats. The eye-clean rate sits at approximately 99%, which means it's genuinely difficult to find a VS2 round that shows anything to the unaided eye. The premium you'd pay to go from VS2 to VS1, let alone into VVS territory, buys you a feature no one will ever see.

SI1 is where things get complicated.

The SI1 and SI2 lottery

Roughly 65% of SI1 stones are eye-clean. That means about one in three will show something to the naked eye. Whether yours does depends almost entirely on where the inclusions sit and what type they are, not on the grade itself.

SI2 is tougher still. About 25% of SI2 stones are eye-clean. Three out of four will show inclusions. That doesn't make every SI2 a bad stone; it makes every SI2 a gamble you should only take when you've examined the actual stone and its inclusion plot.

The grade tells you what the grader found at 10x magnification. It doesn't tell you whether the main inclusion is a central carbon spot sitting in the middle of the table or five tiny pinpoints tucked under a prong near the girdle. Those two SI1 stones look completely different to the naked eye, and the GIA grade alone won't distinguish them.

Buying SI1 or SI2 online without high resolution imagery and a clear inclusion diagram is genuinely risky. Some retailers provide both. Many provide neither. If you can't assess the inclusion location, stay above VS2 when buying sight unseen.

Read the plot, not just the grade

The GIA grading report includes an inclusion diagram. Most buyers skim past it. For SI1 and SI2 stones, that diagram is one of the most valuable tools on the entire document.

Inclusions marked at the edge of the diagram, near the girdle, are almost always invisible in a setting. A prong can cover them entirely. Inclusions marked in the centre of the table are in the worst possible position: prime real estate, full visibility, no hiding place.

Depth matters too. Inclusions near the surface of the crown can catch light unexpectedly. Inclusions buried in the pavilion tend to be broken up by the stone's own brilliance, particularly in round brilliants with good cut grades.

Inclusion type matters most. Feathers (small fractures) and clouds (clusters of microscopic pinpoints that create haze) are the problem inclusions. A central feather in an SI1 can look worse than a peripheral crystal in an SI2. Dark crystals read more harshly than white needles. A single medium sized inclusion sitting directly under the table is more disruptive than ten scattered pinpoints near the girdle.

Count is the least useful metric. Five pinpoints near the girdle beat one crystal in the centre every time. When comparing clarity, location and inclusion type should drive the decision.

Step cuts play by different rules

Emerald cuts are unforgiving. The broad, flat, parallel facets act as windows. Where a round brilliant scatters light through 58 facets and effectively camouflages inclusions, an emerald cut presents the interior of the stone as is. Whatever's there, you'll see it.

VS1 is the minimum for emerald cuts, Asscher cuts, and baguettes. Not VS2. The eye-clean gap between VS1 and VS2 is small for rounds, a percentage point or two, but for step cuts the gap is meaningful. A VS2 emerald that would pass completely unnoticed in a round brilliant may show its inclusions clearly in the step cut geometry.

The price difference between VS1 and VS2 in step cuts is sometimes smaller than you'd expect, partly because the market for very clean step cuts is thinner and the pricing doesn't always fully reflect the visual difference. That creates occasional value: a VS1 emerald cut for not much more than a VS2, and the result is noticeably cleaner.

Lab-grown emerald cuts now sit around 82% below their natural equivalents in price across our index. As step cuts become more accessible at lower price points, we're seeing more buyers choose clarity upgrades rather than carat weight increases, particularly in the VS1 range where the visual payoff in an emerald cut is genuinely apparent.

If you're choosing between shapes and clarity is a primary concern, our guide to eye-clean diamonds covers this shape by shape with real inventory data behind each recommendation.

The FL premium

FL diamonds are rare, and they carry a premium to match. For collectors, that rarity has value on its own terms. For buyers who want to wear a diamond and see it sparkle, FL is the least efficient clarity grade in the system.

The eye-clean rate at FL is 100%. The eye-clean rate at VS2 is approximately 99%. The visual difference between them is nothing.

Spending up through VVS territory and into FL while compromising on cut is one of the more common mistakes we see. Cut drives the brilliance you see every day. A well-cut VS2 will outperform a poorly proportioned FL in any real-world lighting condition. The 4Cs are not equally weighted in practice, and clarity is rarely the one that deserves the most of your budget. Our 4Cs guide covers that priority order in detail.

Grades below I1

I2 and I3 exist in the market and occasionally make sense: estate pieces, fashion settings where the stone is decorative rather than the centrepiece, or buyers whose priority is maximum carat size on a very tight budget with no regard for brilliance.

For any stone where sparkle matters, I2 and I3 are difficult to recommend. I2 inclusions affect transparency and light performance visibly and significantly. I3 can introduce structural fragility; these stones are more susceptible to chipping under normal wear and shouldn't be set in styles with exposed facets.

I1 is the borderline grade. A well-positioned I1 round brilliant, with peripheral inclusions that a setting largely covers, can sometimes be eye-clean or close to it. It requires careful selection and carries real risk without proper examination.

What we're watching

The VS1 to VS2 spread in step cut pricing is worth monitoring over the next few months. If lab-grown step cut prices continue compressing, the incentive for buyers to upgrade into VS1 clarity increases, since the absolute dollar difference between those grades shrinks while the visual difference stays constant.

For rounds, VS2 remains the rational default for buyers under 1.5 carats. The 99% eye-clean rate is as close to certain as the clarity scale gets without paying FL prices. If SI1 is tempting, the work is in the inclusion plot, the inclusion type, and the image quality available from the retailer. The grade alone is not enough information.