Diamond Grading Scale: Complete Guide

If you have any interest in fine jewelry, you probably know that diamonds exist on a spectrum. What makes the stones so rare is that they are all unique. No two diamonds are alike, despite being from mostly the same basic properties. However, these slight differences can alter its appearance and its quality. 

When shopping for a diamond, it is essential that you know what it is worth. This might not always be reflected in the price of the stone; even fake diamonds can be passed off as real ones. Cubic Zirconia is just one example of a very realistic, but not natural, diamond imitation. Without proper certification and grade reporting, you may never know what you’ve just purchased. 

This is why lab grading is so important. If you're about to start the hunt for a stunning engagement ring, a timeless pair of earrings, or even just a beautiful bracelet, don’t overlook this step. We’re here to tell you everything you need to know about how a diamond’s value is decided, so you don’t have to make any guesses!

How Does Grading Diamond Quality Work?

Diamond grading is the best way to guarantee that you are buying a high-quality piece of stone. Without listed scales for individual characteristics of a diamond, the overall grade is based on frivolous properties. Grade reports consider the entire diamond when generating a report, and this helps you to compare different pieces with each other. 

For example, if you have a beautiful colorless diamond, but it is tiny, it may not be as valuable as a slightly colored diamond with a massive carat weight. We’ll get into how these properties stack up against each other later on, but you should always remember that they do all matter. One property might not disrupt the total price of the stone significantly, but it can move it up or down. 

Reputable Labs 

There are many laboratories run by reputable gemologists who create these gemstone grading reports. Each one abides by the grading scale they prefer, but most tend to use the one set by the Gemological Institute of America.

We’ll compare the different laboratories, and you can decide which one works best for you:


The Gemological Institute of America, or GIA for short, is a premier laboratory that functions to educate and train the next generation of gemologists. It was founded in 1931 and has continued to inform the gemology world since. They developed their 4Cs grading system for diamonds after their inception, and it is recognized worldwide. 

Their reports are done by professionals and do not adhere to the whims of private sellers. This is why they are the most reliable and why Mark Henry always relies on GIA Graduate Gemologists for jewelry certifications. 


The American Gemological Society is a more localized grader that bases its grading chart on numbers instead of letters used by GIA. This increases the accessibility of their diamond grading reports because they may be easier to digest for some consumers. GIA reports, while lauded as the best, can be a bit confusing if you don’t know what all of the code words mean. 


There are other privatized diamond graders throughout the world. If you don’t like the work of either the GIA or AGS or you can’t access their services, a simple internet search can pair you up with many other laboratories.

The Four Cs

So, what exactly are the 4Cs? GIA and AGS might break down their scales with different labels, but they both use the original metrics from GIA’s 4C system. The categories are, in order of importance: color, clarity, cut, and carat weight. However, AGS lists them in order of cut, color, clarity, and carat weight. 


The “perfect diamond” to most jewelry lovers is colorless. This is because we appreciate natural diamonds based on their transparency and ability to shine. Colors can impede shine and darken the natural sparkle.

Therefore, color grades are based on a scale of least to most colorful. The naked eye can’t often see small inclusions of color, but under 10x magnification in a laboratory, they are evident. This is why grading reports are so important. 

The GIA system measures diamond color on a scale of D-Z. D diamonds have a total absence of color, but these are not easy to find. Under 1% of all diamonds are in this category. E-F diamonds are still colorless to the naked eye but easier to come across, which makes them great for the average consumer. 

As the scale moves towards Z, slight color is added in. This color is not visible without magnification until you enter the K-L category, and yellow tones are visible easily from M to Z. 

In comparison, the 0-10 scale of AGS places colorless diamonds as a 0 and yellow tinted diamonds as a 10. 

Fancy Colored Diamonds

Diamonds with color have an entirely different color grading scale. Fancy-colored diamonds are considered those that possess a color other than light yellow or brown. Levels of nitrogen can actually create deep yellows, like the popular canary yellow fancy colored diamonds, which are also placed in the separate, colored diamond scale. 

Fancy colored diamonds are ranked as faint, very light, light, fancy light, fancy intense, fancy vivid, fancy dark, and fancy deep. 

The Diamond Clarity Scale

Diamond clarity is important to the overall grade because it determines how easily transparent the stone is. Sometimes, natural inclusions and blemishes can get in the way as the stone is being formed. 

The GIA has a clarity grading chart that goes from flawless to included. Flawless diamonds have absolutely no inclusions or blemishes, while internally flawless diamonds only have some slight blemishes on the outside of the stone. VVSI and VVS2 diamonds are very, very slightly included, with tiny inclusions that can be seen under magnification. VS1 and VS2 diamonds have very slight inclusions with inclusions that are bigger under magnification.

When it comes to S1 and S2 diamonds, which have slight visible inclusions, the value of the stone depletes quickly. Included diamonds 1, 2, and 3 have inclusions that can be seen from under the microscope and are not very desirable. 

AGS measures diamond clarity from 0 to 10 again. 0 is a flawless grade, and anything from 7.5-10 is included.


The diamond’s cut determines its ability to truly sparkle in different types of light. Its brightness and brilliance go hand in hand with its cut grade. GIA uses a cut scale from excellent to poor, and AGS uses the same 0-10 scale with 0 being ideal, 1 being excellent, and 9-10 being poor. 

Brilliant Cuts 

One of the best ways to cut a diamond to maximize light flow is the brilliant cut. It is popular among jewelry artisans and popular in our pieces here at Mark Henry. It was invented in 1919 by Marcel Tolkowsky, who curated this 58-facet design for optimal shine even with inclusions.

You are probably familiar with round brilliant cuts, often featured in diamond rings. It replaced the Old European cut that was favored by collectors in the Victorian, Edwardian, and Art Decor Eras. 

Step Cuts

Another beloved diamond cut is the step cut, with numerous facets that make rectangles and squares. This gives them a wider and bigger appearance, perfect if you want to accentuate a smaller carat diamond. Avoid this cut if your diamond has high inclusions, blemishes, or a poor color grade. 

What Is Carat?

The last component of a diamond grade is the carat weight. This one is fairly self-explanatory; as the numbers increase in carats, the diamond weighs more. Each carat is 200 mg.

However, you should know that since this scale comes last, it is the least important factor. A diamond with a very high carat weight but is Included, and a V color grade is not very valuable. 

Why Does Diamond Certification Matter?

Certification, which includes your diamond grade report, is the best way to know you are making a genuine investment. The last thing you want is to get home and figure out that your brand new diamond ring is a fraud. Imitation diamonds and lab-created diamonds, which have no rarity, are not always easy to spot without the help of a professional. 

The GIA can even put a diamond’s grading right on the piece with a laser. This prevents second-hand sellers from misleading a customer and you from getting a faulty appraisal.

Grading Reports at Mark Henry

Of course, we always want our clients to advocate for themselves. At Mark Henry, you don’t have to worry about fighting for certification. It is provided for all jewelry pieces, every time, as just one of the perks of buying from us!



Learn How to Buy a Diamond with the GIA Diamond Buying Guide | GIA

Diamond Rating Chart & Diamond Grading Tools | American Gem Society

4C's of Diamonds | Cape Town Diamond Museum 

Diamond Quality Factors | GIA

The history of marcel tolkowsky, the creator behind the ideal cut | Cape Town Diamond Museum

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