Is a GIA Very Good cut worth buying in 2026?

Sometimes. A GIA Very Good round returns roughly 5–10% less brightness than a proportion-center Excellent and drops a visible step on fire and scintillation, but retails 15–25% below equivalent Triple Excellent at the same color and clarity. That asymmetry makes Very Good defensible on melee and side stones under 0.10 ct, on halos and pavé where surrounding metal and neighboring stones dominate the look, and on solitaires under 0.50 ct where the alternative is dropping color or clarity. Where Very Good stops making sense is rounds above 1.00 ct as a center stone and anything above 2.00 ct — the light-return delta shows in every glance and resale trims Very Good centers 20–30% below Excellent at trade-in, so you lose on both ends. Read the proportions on the report, not just the grade letter: a Very Good with table 56–58%, pavilion angle 40.8°–41.2°, and crown angle 34°–35° is at the top of its bucket.

AGS vs GIA — which cut grade is stricter on round brilliants?

The two scales measure different things, so "stricter" depends on what you mean. GIA's Excellent grade is proportion-based — table, depth, crown and pavilion angle ranges wide enough that a stone at the center of the ranges and one at the edges both earn the same Excellent grade. The AGS 0 verdict is light-performance-based: AGS ray-traced the actual stone and scored brightness, contrast, dispersion, and light leakage, and only the top tier on all four earns 0. Roughly 10–15% of GIA Triple Excellent rounds also earn AGS Ideal 0; the rest sit somewhere inside the GIA proportion bucket without the light-performance verdict. In practice, AGS 0 is the stricter call on rounds, and GIA Excellent is the wider bucket the trade uses as a floor.

What is the AGS cut grade scale after GIA absorbed AGS in 2022?

GIA absorbed AGS Laboratories in 2022, and standalone AGS certificates stopped being issued. The AGS 0-through-10 light- performance scale still exists — GIA now offers it as an optional supplement to a GIA report on qualifying rounds (and a small set of qualifying fancy shapes) for roughly $25. Lower is better: 0 is Ideal, 1 is Excellent, 2 is Very Good, 3 is Good, 4 is Fair, and 5 through 9 walk down through Poor performance. On a GIA Triple Excellent round the AGS Ideal 0 supplement is what tells you whether the stone is at the top of the Excellent bucket or the middle of it — the same paper, one extra data point.

How much does the AGS Ideal 0 supplement add to a GIA Excellent diamond in dollars?

The supplement itself costs roughly $25 at GIA. The market premium on the finished stone is 5–10% over an otherwise-equivalent GIA Triple Excellent without the supplement — so on a 1.50 ct G VS1 round at roughly $13,000–$16,500 retail, pulling the AGS Ideal supplement that prints 0 protects roughly $700–$1,400 of resale value for a $25 test. That asymmetry is what makes the call easy on rounds above roughly $4,000. If the supplement comes back at AGS 1 instead of 0 you still learn something — the stone is at the top of the Excellent bucket, just not the very top. If the seller refuses to pull the supplement on an eligible stone, that is the answer.

GIA Cut Grade vs AGS 0: The Light Performance Gap Inside Triple Excellent

This is a spoke of our hub How to Read a GIA Diamond Report. The two questions this article answers: on a round brilliant where the GIA report says Triple Excellent, what does the AGS Ideal 0 supplement add — and is the gap worth dollars at your price band?

If you want the scale-versus-scale view, the companion piece GIA vs AGS grading scales covers how the two systems line up overall. This article is narrower: it's about what's happening inside the GIA Excellent bucket on rounds, and how to tell at the counter whether you're paying for the top of the bucket or the bottom of it.

What "Triple Excellent" actually contains

GIA's Excellent cut grade is computed from proportions, polish, and symmetry, with a face-up appearance assessment included. The proportion ranges that qualify a round for Excellent are wide on purpose — the grade is meant to be defensible across the variation a normal cutting operation produces. The ranges:

Table: 52–62%
Depth: 57.5–63.0%
Crown angle: 32.0°–36.0°
Pavilion angle: 40.6°–41.8°
Crown height: 12.5%–17.0%
Star length: 45–65%
Lower-half facet length: 70–85%
Polish: Excellent
Symmetry: Excellent

A round at the center of those ranges performs visibly better than a round at the edges, and both earn the same Excellent grade. That's the gap.

What AGS Ideal 0 isolates

The AGS scale that GIA absorbed in 2022 measured cut on light performance, not proportions. The grading software ray-traces the actual stone and scores brightness, contrast pattern, dispersion, and light leakage. To earn the AGS Ideal 0, the stone has to score top-tier on all four. Roughly 10–15% of GIA Triple Excellent rounds also earn AGS 0; the rest sit somewhere in the proportion bucket without the light-performance verdict.

In plain terms: AGS 0 stones look brighter and more contrast-patterned face-up than the average Excellent. The difference is visible to a careful buyer in real lighting. It's not subtle.

The dollar math on a 1.50 ct round

A representative spec — 1.50 ct, G color, VS1 clarity, GIA Triple Excellent, natural — currently retails roughly $13,000–$16,500 depending on store markup and inscription supplements. Adding the AGS Ideal 0 supplement to that report at GIA costs roughly $25. The resale and trade-in markets price AGS 0 rounds at a 5–10% premium over equivalent Triple Excellent without the supplement. The asymmetry is what makes the call easy:

If you're paying $14,000 for a Triple Excellent and the seller can pull an AGS Ideal supplement on it for $25, the supplement that prints 0 protects roughly $700–$1,400 of resale price. The math is obviously right.
If the supplement comes back at AGS 1 instead of 0, that's still useful information — it tells you the stone is at the top of the Excellent bucket, just not the very top, which is reasonable to know before you pay top-of-bucket money.
If the seller refuses to pull the supplement on a stone that's eligible, that's the answer: the stone almost certainly isn't AGS 0, and you're being asked to pay 0 prices for a 1 or worse.

The companion call on the same report is fluorescence — strong blue can pull 10–15% out of the price on a D–H round regardless of cut, so always negotiate the cut premium and the fluorescence discount on the same conversation, not separately.

When the supplement is not worth it

Three cases. Fancy shapes — princess, cushion, oval, pear — don't always qualify for the AGS Ideal supplement, and even on the qualifying shapes the light-performance science is younger and less universally accepted than on rounds. Skip it on fancies and inspect the stone in person instead. Sub-$3,000 rounds, where the cut premium isn't a meaningful slice of the spend and the GIA Excellent is already enough. And lab-grown rounds under roughly $1,500, where the supplement is structurally a larger share of total stone cost than the value it isolates.

For trade-side context on how the older standalone AGS certificates are still being treated on the secondary market — a question that comes up on estate and pre-2022 inventory — Ajediam's certification provenance notes are the cleanest industry-side reference, particularly on which dealers still honor pre-merger AGS paper at full premium.

Should you buy a GIA Very Good cut?

The tier below Excellent — "Very Good" — is where the real purchase decision lives on melee, side stones, and small solitaires. GIA's Very Good bucket is deliberately broader than Excellent: pavilion angles run 40.4°–41.9°, crown angles 30.7°–37.0°, tables 51–64%. Against a proportion-center Excellent, a well-cut VG round returns roughly 5–10% less measured brightness and drops a visible step on fire and scintillation. In diffuse office lighting the difference is real but not glaring; under spot lighting a jeweler can point it out on the first tilt.

The price spread is where the call gets interesting. VG rounds typically retail 15–25% below equivalent Triple Excellent at the same color and clarity — a materially larger discount than the light-performance loss. That asymmetry makes VG defensible in three specific cases:

Melee and side stones under 0.10 ct — nobody is grading light performance stone-by-stone at that size, and the Excellent premium is paperwork. Take the discount.
Halos and pavé — the surrounding metal and neighboring stones dominate the visual, and VG is invisible next to Excellent at accent scale.
Solitaires under 0.50 ct where budget is tight and the alternative is dropping color or clarity — a VG G/VS beats an Excellent J/SI2 in the mirror.

Where VG stops being defensible: rounds above 1.00 ct as a center stone, and anything above 2.00 ct. At that face-up area the light-return delta shows in every glance, and the resale market discounts VG centers aggressively — 20–30% below Excellent at trade-in, versus the 15–25% retail spread you paid at purchase. You lose on both ends.

How to spot a VG round that face-ups close to Excellent: read the proportions on the report, not just the grade. A VG stone with table 56–58%, pavilion angle 40.8°–41.2°, and crown angle 34°–35° is almost certainly at the top of its bucket — the kind of stone the cutter would have pushed to Excellent if polish or symmetry hadn't dropped a grade. That specific proportion pattern is the VG worth buying at the 15–25% discount. A VG carrying extreme numbers on any of those three axes is Very Good for the right reason and will look it in person.

The same logic on color and clarity — where the grade bucket hides a wider range of actual appearance than the letter suggests — is covered in the 4Cs: which matter most.

The one-line summary

Inside GIA Triple Excellent on a round, the AGS Ideal 0 supplement is the cheapest, most defensible way to tell whether you're at the top of the bucket or the middle of it — pull it on anything above roughly $4,000, walk on anything where the seller refuses. For the rest of the report, return to the hub on reading a GIA report; for the verification step on the inscription that ties the stone to the paper, see reading a GIA laser inscription.