GIA Vs AGS Grading Of Diamonds

There is no way you can be confident about the quality of the diamond you purchase unless you know it is graded by a reputed diamond-certifying agency. Inspecting by the eye can help you analyze minimal diamond properties, especially if you are not much of an expert in diamonds. Diamond certifying labs analyze multiple parameters of the diamonds and grade them accordingly so that buyers can use the grading certificate as a tool while selecting diamonds.

Gemological Institute of America (GIA) and American Gem Society (AGS) are two popular diamond-grading agencies in America. Here is a brief comparison of the various parameters that are taken into account while grading diamonds by GIA and AGS.


The diamond cut grade indicates the quality of the angles of a diamond, its proportions, symmetrical facets, fire, scintillation, brilliance, as well as finishing details. GIA and AGS grades diamond cut differently. GIA uses descriptive word grading method while AGS assigns a number to the cut that is indicative of the cut quality.

GIA cut scale ranges from excellent to poor grade and to arrive at a cut grade value, the agency analyzes seven components of diamonds, namely fire, brightness, weight ratio, durability, symmetry, polish and scintillation. The cut grade, excellent has the maximum glare because the cut reflects almost all light that enters the diamond, and the category usually includes round shapes alone. Very good cut is close to excellent cut in terms of brilliance and in many cases, experts alone can distinguish between the grades by observation. The proportions in a good cut are much different from that of excellent cut, and the diamonds of this grade are more affordable, thereby helping you to stay within the budget. Whatever is the diamond jewelry you are looking to buy, it is not a good idea to choose a poor cut.

The cut scale value of AGS ranges from 0 to 10 with the cut quality decreasing as the grading value increases. 0 stands for ideal cut while 1 corresponds to excellent and so on. Cut scale values from 8 to 10 correspond to poorly cut diamonds.


checking the clarity grade of diamonds will give you a better idea about the number of inclusions and blemishes in it that reduce diamond clarity. GIA uses word-grading system to grade clarity while AGS assesses clarity by assigning numerical values that range from 0 to 10 that are indicative of diamond clarity. On moving from 0 to 10, the diamond clarity goes down.

The clarity grades in GIA grading range IF to I3 and on moving from IF grade to I3 grade, the number of inclusions increases and clarity becomes poor. Multiple number of defects or blemishes can be spotted in a diamond and below given are some commonly found defects in diamonds.

  • Spot- It is the smallest defect and does not have a noticeable volume.
  • Inclusion- The defect inside diamond that appears as a dimensional object with a definite shape, color and size.
  • Cavity- Split in diamond structure
  • Line- A defect that resembles a thin line
  • Cloud- A shaded area inside the diamond.

The AGS grade 0 is equivalent to the IF grade in GIA system while AGS grades from 7.5 to 10 corresponds to I1, I2 and I3 GIA grades.


The color grade of diamonds decides whether it will be colorless or have tints of color in it. GIA color grades range from D to Z and on moving towards Z grade, the color in the diamonds will become more visible. D grade is the best in terms of colorlessness while color grades close to Z will have visible yellow tints that reduce the diamond value.

Like in the case of clarity and cut, AGS assigns numerical values that indicate the amount of color in diamonds and the range of these values falls between 0 and 10. Each color grade value in AGS grading corresponds to a color grade in GIA system. The values 0.0,0.5 and 1.0 corresponds to GIA grades D,E and F respectively while 10 corresponds to the GIA grade X.

Inspecting the diamond by naked eye does not help you distinguish two adjacent color grades but the price will have a significant difference. The grading information gives a better idea about the whiteness of the diamond, but it is still important to confirm it by magnification.

Parameter GIA grading AGS grading
Cut grade Excellent to poor 0-10
Clarity grade IF-I3 0-10
Color grade D-Z 0-10

In terms of popularity, GIA grading ranks first in the US market which is followed by AGS grading. GIA and AGS are independent grading agencies and the presence or absence of AGS or GIA certificate does not have an influence in the pricing of the diamond. Overall, if you are looking for high quality diamonds no need to search no longer! RockHer has a wide selection of high quality jewelry you can choose from. You can even design your own with the help of our well respected experts.

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