GIA vs. AGS | Learn Everything About Diamond Certifications

When it comes to buying a diamond, many factors go into making a choice – but none are more important than certification. There’s definitely no better way to ensure quality than choosing a certified stone from a reputable lab.

The Gemological Institute of America (GIA) and the American Gem Society (AGS) are two of the most trusted names in diamonds. But what’s the difference between them? And which one is right for your needs? 

Here, we compare these two leading labs to help you make an informed decision about your next purchase. So, GIA vs. AGS – which wins? Let’s find out. 

diamonds in the tweezers

AGS vs GIA Diamond Grading Chart: Which Lab Is Best?

While both labs grade diamonds are similar, there are some differences – enough to make each better suited for certain buyers. Let’s compare the two systems of grading diamonds to help you make up your mind.

The Gemological Institute of America (GIA)

GIA is the world’s leading authority on diamonds, with over 1400 scientists and educators working at their headquarters in Carlsbad, California. What began as a small operation in 1931 has since grown into the most respected and well-known gemological organization worldwide.

GIA is known for its rigorous diamond grading standards, which are the most stringent of any lab. It’s also famous for its education and research programs, which have set the industry standard for over 80 years. GIA always stays at the forefront of diamond grading and education with rigorous research, regularly updated grading standards, and dedication to innovation.

GIA is considered the “gold standard” in diamond certification, and most jewelers and retailers like James Allen or Blue Nile only accept diamonds with a GIA report. Similarly, GIA certificates are highly sought after by diamond buyers all over the world, as they offer a high level of assurance that the stone has been graded accurately.

The American Gem Society (AGS)

The American Gem Society (AGS) is a nonprofit trade organization founded in 1934 in Las Vegas, Nevada, with a goal to set the highest standards in the gemstone industry and protect the interests of consumers.

In the early days, AGS focused more on gemological research and education. However, as technological advancements transformed the way diamonds were cut and graded, AGS laboratories began to focus on diamond grading. As they’re competitors with GIA in the lab world, they set out to create their own superior grading mechanism.

Even though AGS’s own grading system was developed later than GIA, many people find AGS Labs superior. According to some industry experts in the diamond market, AGS’s stricter standards produce more accurate results. The grading system is also considered more straightforward and easier to understand.

However, the AGS diamond grading mechanism is still less widely adopted than GIA’s by US jewelers and diamond buyers. 

What Sets AGS Apart From GIA?

The main difference between AGS and GIA is that they have different processes for grading diamonds. Here’s a look at how GIA and AGS grade the most important quality factors in diamonds:


Regarding diamond cut grading, GIA rates that on a 5-point scale from Excellent to Poor, while AGS’s cut grading system uses a 0-10 scale, with 0 being the best. The main difference is that AGS grades identify specific points important to diamond quality regarding cuts, such as brightness, fire, and symmetry. Those are then delivered to the customer in AGS reports.


GIA provides the diamond clarity grade on a 5-point scale from Flawless to Included, while AGS uses a 10-point clarity grading scale from Flawless to Included. With AGS diamond-graded jewelry, the higher the grade, the more blemishes or inclusions the diamond has.


GIA grades diamond color on a scale from D (colorless) to Z (light yellow). AGS uses its usual 10-point scale, with 0 being colorless and 10 being light yellow. Additionally, after the 10-point scale, there’s “Fancy Yellow,” which is essentially anything above a yellow grade – something that the GIA scale doesn’t have.

Carat Weight

When it comes to assessing diamond carat weight, both AGS and GIA employ similar processes. However, AGS stands out for its slightly higher precision in measuring carat weight, using three decimal points compared to GIA’s two. This precision may appeal to those who prioritize exactness in determining a diamond’s weight, highlighting the commitment of both organizations to thorough diamond assessment.

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AGS vs. GIA Diamond Certification: Price Differences Between Laboratories

Whichever of the gemological labs you choose, the diamond certification or grading report will cost you.

Generally, GIA grading costs about 30% more than an AGS report because it’s more widely adopted by jewelers in the US and worldwide, so their diamonds tend to be priced higher than those of an AGS lab. AGS diamonds are typically priced lower because they’re not as well known. But as the lab grows in popularity, this is starting to change.

So, if you’re looking for a high-quality diamond and price is a factor, AGS-certified diamonds may be a better option. But if you don’t mind spending a little more, GIA-certified gems are a safe bet.

In the end, it really comes down to what’s important to you and your budget. GIA and AGS are both excellent labs with rigorous grading, so you can’t go wrong with either one.

What Is the Difference Between AGS and GIA

GIA and AGS share common ground in grading color and clarity grades while providing detailed diamond measurements. The pivotal disparity lies in cut grading, where AGS excels in a comprehensive analysis, delving into factors like light performance and facet alignment. This meticulous approach by AGS offers consumers a deeper understanding of a diamond’s cut quality, enhancing their appreciation of its brilliance and overall visual allure.

Which Diamond Lab Certification Is Best?

So, as you can see, there are some key differences between how GIA and AGS conduct their grading. But which one is better? 

close up of a diamond ring

Well, that depends on what’s important to you. If you’re looking for top-notch diamond cut quality, then AGS is probably the better choice. But if you care more about color and clarity grading, GIA is the better option.

Ultimately, the best way to decide between AGS vs. GIA is to compare diamonds graded by both labs side-by-side. This will help you see the differences in their grading process and make an informed decision about which lab is right for you.

Yet, if you’re still confused between the two grading labs, here’s a recap:

GIA Certification:

• Ideal For: An experienced buyer with a high budget; or someone looking to sell valuable diamonds in the future.

• GIA Advantage: By far the most complete and detailed diamond grading reports in the diamond industry. Widely recognized, with a high level of consistency due to its rigid standards.

Price: More expensive than AGS (the price difference can be around 30% more),

AGS Certification:

• Ideal For: A first-time buyer on a budget; or someone looking for an excellent cut grading.

• AGS Advantage: Stricter grading standards result in more accurate grades – especially for cut and symmetry.

Price: 30% less than the GIA diamond certificate.

All in all, GIA and AGS are both highly respected laboratories with rigorous grading systems. They both have a high ethical standard, and their grading results are consistent and reliable. So whichever one you choose, you can rest assured that you’re getting a top-quality jewel.


FAQs on GIA vs. AGS

What Is AGS-Certified Diamond?

An AGS diamond certification is a diamond that has been graded by the American Gemological Society (AGS). The AGS grading lab is one of the most important gem labs that use a strict grading system to determine a diamond’s quality.

Are GIA Diamonds Worth More?

Is GIA certification important? Yes, indeed! GIA-certified diamonds are generally priced higher than AGS-certified diamonds. This is because GIA is the most widely recognized lab globally, which increases its market value. AGS diamonds cost less because they’re not as well known, but this may change over time.

Which Is Better: GIA or IGI?

Well, that depends on what you’re looking for. Generally, the GIA and the International Gemological Institute (IGI) are both highly respected gemological laboratories.

two diamond rings

However, IGI is more affordable and has a wider range of price points. But some jewelers find the system to be too lenient – so don’t expect IGI diamonds to maintain their value as well as GIA ones, for example. In contrast, GIA is more popular because it’s a more detailed system that gives you a better understanding of a diamond’s properties.

Why Are Diamond Certifications Important?

Diamond certifications help give diamond buyers and jewelers the information they need to make an informed buying decision. Diamond certificates are accepted by both parties as proof of a diamond’s authenticity. They also provide a guarantee that the diamond hasn’t been altered in any way since it was graded, so you shouldn’t overlook your diamond certificate.

If I Get My Diamond Certified by GIA, Can I Still Get It Appraised by AGS?

It’s not common, but it’s possible. However, diamond appraisers use different grading scales, so there may be discrepancies between AGS-graded diamonds and GIA-graded ones, even if it’s the same diamond.

Conclusion on GIA vs AGS

At the end of the day, both GIA and AGS are top-quality labs and certified diamond graders. They both have a rigorous grading system, and their reports are reliable and consistent. So, ultimately, the decision comes down to you: your preferences, style, and desired price point.

If you’re looking for a diamond that’ll maintain its value over time, then go with the GIA. But if you’re looking for an affordable option with good quality, AGS is a great choice.

What matters most is that you know exactly what you’re buying. This is why it’s important to ask the right questions before purchasing any diamond, regardless of which lab it comes from.

Happy diamond hunting!

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