gia vs ags

 Bottom Line Recommendations

  • Both the GIA and the AGS are considered two of the best diamond grading labs in the world. It is easy to view them as competing for grading labs. However, since they are so similar in their grading methods and since they were created not to compete with each other but to fill a niche, it is better to consider them as sister organizations.
  • That said even with the similarities the GIA is more widely accepted than the AGS. View more here. This is thanks to the fact that it is a grading system is easy to comprehend. Both labs, however, have taken measures to ensure that their grading is consistent with each other. However, the AGS cut grade is considered superior to the GIA cut grade. Take a look at the GIA vs AGS diamond cut comparison below.
  • Keep in mind that while AGS is much smaller than the GIA, it is an equally important diamond grading lab. Find out more here. Its diamond cut analysis is considered superior to the GIA diamond cut. This is understandable as it was set up to fill a gap that was not covered by the GIA.
  • While it is recommended to go with the most popular diamond grading lab, which is the GIA, note that the AGS still offers reliable information on the quality of a diamond and is used by many diamond sellers worldwide. Take a look at a good example here.
  • Both the AGS and the GIA use a similar procedure for their color grading. In fact, AGS has taken measures to ensure that the color grading is consistent with the GIA. Both diamond labs have master stones which they use to compare with each new diamond before assigning a color grade.

When you are searching for your ideal diamond, it is crucial for you to understand what you are spending your money on.

When it comes to diamonds, it is the grading labs that provide you with its specifications. There are many grading labs in the world. Note that every lab will have its own way of grading its diamonds which means that the lab reports will appear different even while referencing the same diamond.

James Allen Diamonds

Two of the most popular and most recognized grading labs are AGS and GIA. Both have designed an easy way of judging the cut, carat weight, color and clarity of the diamond. There are some other well-known labs such as the EGL. Find out more here. However, we recommend getting a diamond that has been certified by either the GIA or the AGS.

The GIA – Gemological Institute of America

The GIA is the leading diamond laboratory. It is used by diamond buyers and sellers all over the world.  This diamond lab was set up in 1931 and is accredited with developing the diamond 4Cs. It also developed the international grading system which is still in use today.

The GIA headquarters are found in Carlsbad, California. They have, however, facilities that are located in all the major cities and trading centers in the world. The GIA has over 1400 employees, including diamond educators, scientists and certified graders.

The GIA conducts intensive research and this puts it at the forefront in the diamond industry.

The AGS – American Gem Society

The AmericanGem Society is not as old as the GIA having been founded in 1996. It has set itself as one of the best diamond labs owing to its attention to detail and intensive research. In fact, the AGS has paved the way into diamond cut research and has helped customers decide on the best cut for their diamonds.

The GIA and the AGS have one thing in common—they were both founded by Robert M Shipley. It’s important to note that the AGS wasn’t founded to compete with the GIA and other diamond labs.

Shipley and the other founders had noticed a gap in the cut of the diamond left by the GIA and this was the main reason for setting up the AGS.

GIA vs AGS – Diamond color

The GIA grades diamond color on a D-Z color scale. The most colorless diamonds are given the D color grade while those with the most tint but are still categorized as colorless diamonds are given a Z color grade.

Diamonds that have more color than the Z color grade are called fancy color diamonds. To remain consistent when grading the diamond, the stones are evaluated under strict lighting conditions and compared to master stones held by the lab.

The diamonds that are in the D to R range of the color scale will have minute differences that are not noticeable to the naked eye. Those between S-R will be noticeable to the naked eye.

The AGS has a similar method of judging the color of a diamond. It has also included a few measures to stay at par with the GIA method of grading diamonds.

The main difference is that the AGS uses a 0-10 color scale. A diamond in the 0-color grade is a completely colorless diamond. On the other hand, a diamond in the 7.5 to 10 range is a slightly colored diamond.

Yellow diamonds have a separate grading system.

GIA vs AGS – Diamond Clarity

The GIA has a clarity scale that starts with the FL or flawless diamonds. These are diamonds that have no blemishes or inclusions. Blemishes are the surface imperfections while inclusions are imperfections found inside the structure of the diamond.

The scale also includes diamonds that have inclusions that can only bee is seen under 10X magnification to inclusions that can be seen by the naked eye. This grade on the other end of the scale is the I1, I2, and I3 also known as the included diamonds.

The GIA diamond clarity scale is recognized the world over and accepted as the standard.

Similar to the color grade, AGS uses a similar fashion to judge the clarity of diamonds. The scale, in this case, starts from 0- to 10.

The AGS 0 grade is similar to the GIA flawless grade. The 9.5-10 clarity scale is the same as the GIA I3 grade.

GIA vs AGS – Diamond cut

The GIA only offers a cut assessment on the round brilliant cut. There are no plans of extending this to the other fancy cuts.

There are no other cut grading systems that are scientifically verified other than the AGS cut scale. This proportion-based scale can be used on different diamond shapes and different diamond sizes.

The GIA cut scale uses a more analytical and computer-based system to judge the proportions of the diamond.

Basing on the cut of the diamond, the scale ranges from 1 to 10. The highest and best grade that a diamond can be given is 1. The diamond buyer will also receive plenty of information under this cut grade including the profile, the symmetry, the carat weight, the diamond proportions and is also given a final grading.

The AGS cut scale is recognized by the majority of diamond sellers and is held to high standards. Take a look below.

ExcellentVery GoodGoodFairPoor


There is a reason the GIA cut scale is so widely accepted. The GIA diamond lab itself was created by people who had a vast knowledge of the diamond industry. The GIA didn’t prioritize on light performance. This is because they were afraid that focusing too much on light performance would cause them to sacrifice on the carat weight.

At the end of the day, retailers would never want to sacrifice on the carat weight based on the cut of the diamond as more skill, precision and time are needed. This will make the process even more expensive.

GIA vs AGS – Diamond Carat

AGS and GIA have a similar process for judging the carat weight of a diamond. Keep in mind whenever you are deciding on either GIA or AGS however, that while the GIA uses two decimal points, the AGS uses 3 decimal points which makes the AGS more accurate.

The main difference between the GIA excellent and IGS Ideal

The main difference between the GIA’s excellent cut grade and the IGS ideal cut grade is found mainly in the parameters. The AGS seems to have much tighter parameters than the GIA.

That said, what sets the GIA apart from all the other diamond labs is their adherence to consistency.


Both the GIA and the AGS are the two of the leading diamond labs in the world. When compared side by side, it is the GIA that seems to have an edge over the AGS as well as all the other diamond labs.

That said, the AGS cut scale is considered superior to the AGS. This is not to say that you cannot get an ideal cut diamond using the GIA scale. Start off by understanding the proportions of the diamond shape that you want.

When it comes to the clarity scale of the diamond, the AGS is a bit inconsistent. There seems to be a larger disparity in judging clarity between these two diamond labs. This can prove a bit challenging for the diamond buyer. It is not the best thing to buy a diamond that is rated as slightly included in the AGS report but is rated as included in the GIA report.

Note also that the AGS will give fancy cut diamonds a cut grade. However, the GIA will not offer a cut grade to fancy cut diamonds. The GIA only gives the round brilliant cut a cut grade.

Also note that while the AGS will use the 4Cs to judge the quality of their diamonds, they have established their own unique method for diamond grading. They also have many different grading reports compared to the GIA.

Whether you plan on buying your diamond with a GIA certificate or an AGS certificate, it is not recommended that you buy your diamond based on the reports alone. Always make sure that you view 360-degree videos of the diamond to best judge the appearance.

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