GIA vs. AGS - Institutes To Grade Diamonds

What are GIA certificates? What is AGS? Which one is better? Maybe you have these questions in your mind right now while searching for diamonds and learning everything about them to get the best one for your money. Let's start with a clarification because this will be very important for you to buy a real diamond worth it and not a fake one.

GIA and AGS are institutes to grade the quality of diamonds. They have their own reports and certificates which you cannot directly compare to each other. I will give you all informations about these institutes, their history and how you can read their certificates.

Very Important

First of all, my recommendation:

Only buy diamonds with GIA or AGS certificate!

These two institutes certify most consistently and thus make it comparable. They also rate strictly, so you always can be sure that a quality certified by GIA or AGS really is the quality you expect and the price is absolutely justified.

Diamond Grading Institutes

Personally, I am very safety-conscious and have informed myself at the beginning of my search which online shops I can trust. This quickly led me to the certificates of GIA and AGS, which determine the quality of the diamond. These institutes are really important for the whole diamond business because in businesses with a lot of money there is always fakes and fraud. Especially in the online shopping you cannot directly proof the quality by investigating and touching the jewel so you need some independent certificate that ensures you to get what you should get.
Let me explain which certificates there are and which ones you can trust.

Now there are various institutes that certify diamonds, for example:

Differences Between The Institutes

It is important to know that each institute has its own scales and units and therefore certifies differently than the others. That means that each certificate is not comparable to another and so it is very important that you always use the certificates of the same institute when looking for a diamond in order to make the results comparable.



It could be that the EGL certifies the color of a diamond with an "H", but the color at the AGS would be an "N". Unfortunately you only see how yellowish the tone is after ordering the diamond. So this is my advice: firstly find the desired color of the diamond, for example through James Allen or Blue Nile, and take the value in the certificate from GIA as reference value. Never mix several certificates! You can do the same with an AGS certificate.

Certificates, that are not issued by GIA or AGS, are always in danger of showing diamonds more valuable on paper than they are in reality. This does not happen because the institutions give false informations, but simply because they use other scales and techniques that do not come close to the quality of GIA or AGS.

As a result, some people have been shown diamonds to me that were supposed to be a bargain, if you look at the price and the certificate. But in the end, it was only the fact that different scales were used, which make the diamond appear more valuable than it is.

GIA vs. AGS - History and Certificates


"Established in 1931, GIA is the world's foremost authority on diamonds, colored stones, and pearls. A public benefit, nonprofit institute, GIA is the leading source of knowledge, standards, and education in gems and jewelry."

On the GIA website, the history and origins of the institute are presented in a very cool way. You are welcome to have a look at it if you are interested in history (GIA History). I will not talk about it here to limit myself to the essentials.

GIA is the inventor of the famous 4 C's, which are known everywhere today and are used for the certification of diamonds. These units were developed in the 1940s.

GIA definitely holds the largest market share with AGS and has distinguished itself through its technology, approach and quality. Certificates from GIA are absolutely trustworthy!

On the right hand you can see a GIA Report Sample.


"The American Gem Society (AGS) was founded in 1934 by a small group of leading jewelers Their goal was to create an organization that could help protect the jewelry-buying public from fraud and false advertising. Today, we're proud to say their vision has become a reality."

AGS was probably the first institute that certified diamonds. So they had a monopoly in the beginning and their certificates were traded like gold because they were trustful and the biggest diamond traders in the world worked with them.

After GIA entered the market, AGS's market share decreased significantly, so that these two institutes now hold the lion's share of the market. For us as consumers, there are only few differences between these two, so I will not go into detail. AGS can certify diamond cuts better, but the most important thing as I mentioned before: AGS certificates are absolutely trustworthy!

On the right hand you can see an AGS Report sample.

The Content of GIA Certificates and AGS Reports

Cut Grade Clarity Grade Carat Weight
Color Grade Depth Table
Diamond Shape Fluorescence Grade Polish Grade
Symmetry General Comments And some more...


Now you got a lot of informations about the diamond certificates that hopefully will help you to find a jewel of very good quality. I wouldn't say that GIA or AGS is better or trustworthier. Both institutes have high quality certificates. But be careful if your desired diamond only has a certificate from another institute or even worse, it doesn't have any certificate.
I can only repeat myself: never buy diamonds without GIA or AGS certificates!

Nevertheless, let me tell you one thing: the certificates only assure you that your diamond really is of the quality you pay for. But they can't take away the decision if the diamond is visually attractive or if your wife will like it. You still have to decide that separately from the paper. Yes, I know it is not easy, but this process is fun and if you find a diamond that touches your and her heart and you have created a connection to it, you will be incredibly happy!