How to Buy a Diamond: Everything You Need to Know

On the engagement ring hunt? Congrats to you! For most people, buying a diamond is an entirely new experience – one that can feel very overwhelming. But it doesn’t have to be.

With the help of Blue Nile, the true experts in diamond buying, we’ve put together all the information on how to buy a diamond in a simple, straightforward way so you can make the right choice for you and your soon-to-be fiancé.

How to Buy a Diamond

how to buy a diamond

The first thing to know is that all loose diamonds from Blue Nile (and any reputable jeweler) are graded and certified by an independent laboratory. Their grade is given unbiasedly based off of a few scales that organizations like the GIA or AGSL use. The grade a diamond is given directly affects how much you pay for it and buying a certified diamond is very important.

Next, the major characteristics to understand about a diamond are: SHAPE, CUT, COLOR, CLARITY, and CARAT WEIGHT. Let’s go down this list one by one.


The shape you choose – which is typically based on personal preference – can change what qualities to look for in each diamond. Therefore, you should pick 1-3 shapes to look into and find out all there is to know about each shape. Here’s a good run down of all the diamond shapes and what you should look for in each, and below is an easy chart you can use:

Diamond Shapes - How to Buy a Diamond


The cut of a diamond determines how light moves through it and ultimately determines a diamond’s brilliance – AKA its sparkle or shine. It’s the most important characteristic in a diamond because it has the greatest overall influence on a diamond’s appearance. The sparkle of a well-cut diamond can also make it appear larger (which most people would tell you is a huge plus).

When a diamond is cut with the proper proportions, light is returned out of the top of the diamond (see the “ideal” visual below). If it is cut too shallow, light leaks out of the bottom. If it’s too deep, it escapes out of the side. You want the light to reflect out of the top of the diamond, also known as the table, to get the most sparkle.

There is a cut scale put forth by the GIA that goes as follows: Excellent, Very Good, Good, Fair, and Poor. Diamonds with the highest grades cost more money for three reasons:

1) They are far more rare
2) In order to cut such a beautiful stone, you need a highly-skilled/experienced diamond cutter
3) It simply takes a lot more time to produce a well-cut stone

Blue Nile has an entire section on diamond cuts, if you want more details!


In the diamond world, when we talk about color, we’re actually referring to a diamond’s lack of color. Colorless diamonds are the best quality, as they appear the whitest. The highest grade is a D and the scale goes all the way down the alphabet to K-Z, at which point diamonds begin to have noticeable color. Blue Nile only carries J or higher which is a safe cut off to stick with no matter where you buy.

Diamond color scale

To break down the scale even further…

Absolutely colorless: The highest color grade; Extremely rare.

F-E Colorless:Minute traces of color can be detected by an expert gemologist; A rare diamond.

H-G Near-colorless: Color difficult to detect unless alongside diamonds of better grades; An excellent value.

J-I Near-colorless: An exceptional value with slightly detectable warmth or tone.

M-K Noticeable color: not carried by Blue Nile

Z-N Noticeable color: also not carried by Blue Nile


Clarity refers to the tiny, natural imperfections that occur in all diamonds (except the very, very finest diamonds). Gemologists refer to these imperfections by a variety of technical names, including blemishes and inclusions. Diamonds with the least and smallest imperfections receive the highest clarity grades. Because these imperfections tend to be microscopic, they do not generally affect a diamond’s beauty in any discernible way.

clarity-of-diamonds chart

Here’s that scale written out:

FL: Flawless, Internally Flawless // No internal or external imperfections.
IF: Internally Flawless: No internal imperfections // Very rare.
VVS1 + VVS2: Very, Very Slightly Included // Very difficult to see imperfections under 10x magnification. An excellent quality diamond.
VS1 +VS2: Very Slightly Included // Imperfections are not typically visible to the unaided eye. Less expensive than the VVS1 or VVS2 grades.
SI1 + SI2: Slightly Included // Imperfections are visible under 10x magnification, and may be visible with the unaided eye. A good diamond value.
I1: Included // Blue Nile offers a limited selection of jewelry with diamonds of I1 grade clarity. This grade of diamonds will have minor inclusions that may be visible to the unaided eye.
I2 +I3: Blue Nile does not carry diamonds of I2 or I3 grade clarity


Carat weight

Carat is a measure of a diamond’s weight. It does NOT fully reflect the visual size of a diamond as most people casually believe. We often think that more carats means a bigger diamond but there is more to it than that. It’s important to look at the carat weight alongside the cut and measurements. If a diamond is poorly cut, the weight could be “hidden” in the base of the diamond. It is just as important to measure the distance across the top of the diamond (aka the table) as this is how we view a stone when it is set into a ring.

The table is measured in millimeters and Blue Nile’s diamond carat size chart can help you visualize it. Here’s a snippet from the chart:

diamond carat size chart

That about sums it up, fellas! With a basic understanding of the grading scales, you should feel more prepared to buy a diamond. It’s not as crazy of a process as you might fear, and becoming educated on it is a big part of all the fun. It’s your moment to shine (alongside the ring) and we’re very excited for you to find your fiancé’s dream engagement ring!

How to Buy a Diamond

If you have any unanswered questions, Blue Nile’s education section covers everything you need to know. They go into figuring out your budget, finding the right metal, fancy colored diamonds, and more!

If you’re looking for ways to propose, be sure to check out our proposal idea finder. We also have vendors to help you plan and photographers to capture the moment forever. And as always, be sure to get that ring and diamond insured – here’s how to find the best engagement ring insurance policy for you.

Good luck, and let us know how when she says ‘yes’!