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The 9-Step Guide to Buying a Diamond

Tips for buying your diamond engagement ring to get the best bang for your buck

Michael Fried
Michael Fried

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    We are reader-supported. Buying through links on our site may earn us commissions. Learn More.

Why this Diamond Guide?

One of our readers was working with Annie recently and asked her about this diamond from Blue Nile. Now her first reaction was that the diamond was stunning. but then she asked what setting it will go in. When the reader responded with this setting, we realized it would have been a terrible mistake.

This article is for anybody looking to buy a loose diamond (either by itself or with an engagement ring as a “build your own” set) online at one of the many online diamond vendors.

Sometimes I forget just how difficult it is for a consumer to juggle all the information when figuring out if something is a good price. My team and I have so much experience selecting diamonds (each of us selects hundreds every month), navigating the minefield becomes second nature for us.

For example, if you were to ask me for a 1 carat round diamond to put in a halo, it would take me about 15 seconds to find this gorgeous diamond on James Allen for you. Another 20 seconds, and I’d add this great alternative on Blue Nile. But searching on your own can be excruciating and filled with doubt. If you want a little peace of mind, feel free to contact us for some personal advice.

If you’ve been around our site before, you’ll see that we generally recommend buying from Blue Nile or James Allen.  For an explanation of why that is, you can read our individual site reviews for James Allen and Blue Nile.

How to Pick a Diamond

Choosing a beautiful diamond involves narrowing down your shape and selecting high-quality options for the 4Cs — without overpaying. You’ll then compare individual diamonds to see which one offers you the most brilliance and fire. Follow our step-by-step guide below to find a stunning diamond while staying within your budget. Budgets can vary a lot from one person to another, so make sure you’re comfortable with the money you want to spend (for example, if your budget is around 4k, hop in our $4000 engagement ring article after you read this 9 step guide to get inspired). 

We recommend reputable online diamond vendors. Based on our years of experience, James Allen and Blue Nile have proven to offer the best selection at the best prices (see the full list of Best Online Jewelry Stores here). Because their overhead costs are low and they don’t keep an inventory in-house, you’ll find the best deal with these two vendors. Both James Allen and Blue Nile provide HD and 360° imagery so you can compare diamonds up-close before purchase. 

1. Choose Your Diamond Shape

The shape of your diamond is the launching point of your ring’s design. No shape is better than the other—it’s up to your personal preference (or your partner’s). Round Brilliants are the most popular diamond shape for engagement rings and give off the most brilliance. Others prefer a more unique shape like a Cushion Cut or an Oval. If you’re unsure what your partner prefers, you can ask her family and friends.

Select a shape to narrow down your search and compare diamonds.

Choosing a diamond shape on Blue Nile

Choosing a diamond shape on James Allen

2. Select Your Carat Weight

Is your fiance-to-be expecting a 1 or 2 carat diamond? Are you looking for a stone that’s noticeable but not over the top? Choose the carat weight range you’re open to considering, such as a 0.95 to a 1.08 Carat diamond. As carat weight increases, so does the price.

Blue Nile

How to choose carat weight on Blue Nile

How to choose carat weight on James Allen

James Allen

Carat weight impacts how large a diamond looks (as does its shape and cut quality). Learn about the average diamond size people buy to help you decide.

3. Narrow Down on Cut Quality

The aspect that most greatly impacts a diamond’s beauty is its cut quality. Cut grades aren’t standardized across all vendors, but in general, we recommend only Excellent and Ideal cut diamonds. 

For example, on Blue Nile’s site for round diamonds, you should limit your selection to Ideal and Astor Ideal diamonds. On James Allen, choose Ideal and True Hearts cut.

How to choose diamond cut on Blue Nile and James Allen

Reviewer’s Advice

My advice for cut grade is this: If you are looking for a round brilliant diamond, only search for “Ideal/Excellent” grade diamonds.  If you are searching for a fancy shape, however, then it might pay to either include “Premium” or to disregard the cut grade altogether.

This is not to say that cut grade is not important – on the contrary, it’s of utmost importance. It’s simply saying that many vendors don’t correctly report fancy shape cut grades, so why filter out many results from your search which might be great choices.

4.Determine Color Grade Range

The goal with diamond color is to choose a diamond that appears white. But you don’t need to pay for a D or E diamond to get a colorless stone. In general, diamonds in the G to I range appear white but cost far less.

It is important to remember that different shapes reflect color at different strengths, so your choice of optimal color, balancing the diamond’s appearance with the diamond’s price, will depend greatly on what diamond shape you’ve chosen.

How to choose diamond color on Blue Nile

How to choose diamond color on James Allen

Think You’re A Diamond Pro?

Think you’re a Diamond Pro and can save 25%?
Choose the diamond that you like better.
Is it the J color for $4,082 or the G color for $5,500?

5. Select Clarity Grade

For Clarity, you should look for a diamond that’s eye clean, meaning you can’t see any blemishes or inclusions with the naked eye. Depending on the shape, you can usually find an eye-clean diamond in the VS1VS2 range. There’s no need to pay for a FL or IF diamond when you can get a lower graded diamond for much less.

With most vendors, you can see the diamond up close to review its clarity. For example, with James Allen’s “Virtual Loupe” you can evaluate a loose diamond before you buy it.  Blue Nile has also begun to offer high quality photography. Look at the diamond closely to see if you notice any blemishes.

For an informative overview of the different clarity grades, take a look at this diamond clarity chart.

Eye-Cleanliness is Paramount

In our opinion, a consumer’s goal should be to find the cheapest (in regards to clarity; other factors matter as well) “eye-clean” diamond you can find. We use “eye-clean” to describe diamonds that may have inclusions if you look at them with a magnifying glass (or microscope or loupe), but the typical person can’t see the inclusion with their naked eye.

We have recently developed Ringo, a patented artificial intelligence model, that can examine videos of diamonds and determine if they are eye-clean. Ringo will also filter for other parameters like making sure the diamond is well-cut, doesn’t have fluorescence issues and will match the style setting you choose. 

Ringo Approved Eye Clean Diamonds

6. Compare Similar Diamonds

Once you’ve narrowed down your preferred specs for a diamond, compare similar stones to determine which one to buy. You’ll want to consider aspects like how brilliant the diamond is, if it’s eye-clean, and what the price is.

Blue Nile Visual diamond selecting

James Allen visual diamond selecting

Blue Nile selected diamond

James Allen selected diamond

Other characteristics like fluorescence, polish, and symmetry affect a diamond’s value and appearance to some degree, although much less than the 4 C’s. For an in-depth discussion of these three factors, check out these individual articles: Fluorescence, Polish, and Symmetry.

7. Verify the Certificate

You should consider only GIA Certified Diamonds and AGS Certified Diamonds in your search for a loose diamond.

Verify GIA on James Allen

Stay away from IGI, EGL, and HRD Certified diamonds because we’ve found in our professional experience that their results are not reliable due to their inconsistent grading.

Read more about GIA diamonds here.

8. Get an Expert Opinion

Before making the big decision to buy a diamond, have one of our impartial experts review your choice. We’ll give your diamond a close look to see if we recommend the purchase. Having an expert’s opinion ensures you get the best diamond for your budget. You’ll also have more confidence in what you’re buying.

9. Make the Purchase

Once you feel confident in your diamond, buy it online along with a ring setting of your choice. Follow our insider tips for how to determine the type of setting she’ll love

With most online vendors, they offer hassle-free returns within 30 days. If you or your partner aren’t 100% satisfied with the ring, you can get your money back. Almost every reader that goes through our process for picking a diamond is extremely satisfied with their purchase.

If you have any questions throughout the engagement ring process, feel free to reach out to us for diamond advice.

James Allen James Allen is the leader in online diamond sales. Their imaging technology is the same as inspecting a diamond with a jeweler's loupe. They have the largest exclusive loose diamond inventory online and fantastic prices. They also have the nicest collection of lab created diamonds online. Save 25% on studs and earrings! and  Save 10% off Lab Created Diamonds during limited time sale!
What we love about them:
  • No questions asked returns within 30 days of shipment. James Allen will send you a paid shipping label to return the ring.
  • Lifetime Warranty
  • Free International Shipping
  • Free prong tightening, repolishing, rhodium plating and cleaning every 6 months
  • Provide insurance appraisals
  • One free resizing within 60 days of purchase
  • Free ring inscriptions
  • Best-in-class high quality imagery of all diamonds in stock
  • 24/7 Customer Service
  • Best-in-class packaging
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Blue Nile Blue Nile is the largest and most well known internet jewelry seller. They have a very large exclusive online inventory. Their high quality images are catching up to James Allens' and their prices are amazing. Blue Nile have generously offered our readers an exclusive one-time use coupon. (Click Here to save $100 off engagement ring settings)

Please enter your email address to receive your personal one-time use unique coupon code - 15% Off:

What we love about them:
  • No questions asked returns within 30 days of shipment. Blue Nile will send you a paid shipping label to return the ring.
  • Lifetime Warranty
  • Free Shipping
  • Free prong tightening, repolishing, rhodium plating and cleaning every 6 months
  • Provide insurance appraisal
  • One free resizing within the first year of purchase
  • High quality images of about half of their diamonds
  • 24/7 Customer Service
  • 100% credit towards future upgrades (must be at least double in value)
  • Best in class fulfillment
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