Are Costco Diamonds Good Quality? (Review, Value + More)

Are Costco Diamonds Good Quality

Lindsey, do you know if Costco diamonds are good quality? This is one of the questions our readers ask a lot. Well, we´ve got you covered.

Buying a diamond can be a huge investment of time and money, so it is for sure true that you need to inform yourself before you set out to find the perfect sparkler.

You get a screaming deal on everything else at Costco, so should you look to the warehouse for diamonds, too? 

Costco claims that all diamonds are at least I color, VS2 clarity, and very good to excellent cuts; however, not all diamonds have GIA certificates, so it is difficult to guarantee quality. Costco prices are comparable to or slightly cheaper than online jewelers, and much cheaper than brick and mortar jewelers. 

You can get a great deal on a diamond at Costco, though it isn’t guaranteed. Read on for everything you need to know about Costco diamond quality. 

Are Costco Diamonds Cheaper? 

It depends. The best deals in diamonds are found online these days, at sellers like Blue Nile, James Allen, and Brilliant Earth. 

For diamonds over 1 carat, Costco might beat these online sellers by a small amount; however, that doesn’t necessarily mean you will want to go with Costco for your diamond needs (see below). 

Costco is a much better deal for diamonds under 1 ct. Again, however, this may be due to the fact that Costco doesn’t provide a GIA certificate for these smaller stones, so you aren’t sure what you are getting.

It is difficult to evaluate cut for these stones, and cut is extremely important in making a diamond sparkle and shine. 

Costco definitely beats the prices of brick and mortar or mall jewelers, sometimes selling rings for half the price. 

Read also >> Costco Jewelry Return Policy (Rings, Damaged Jewelry, Repair)

Read also >> Where to Buy GIA Certified Diamonds (11 Best Places)

Are Costco Diamonds Good Diamonds?

Probably. All Costco diamonds are claimed to be no lower than I color (near-colorless) (though some secret shoppers have claimed to have seen J grade diamonds at Costco passed off as I color). 

All stones are at least VS2 clarity, which means you should not be able to see inclusions with the naked eye. 

Costco also claims that all cuts are very good to excellent, though this is difficult to tell without the GIA certificate. 

Costco does sell some very high-quality gems on its website, though if you are looking for better quality than that listed above, you will have very limited options at Costco. 

For diamonds over 1 ct you will receive a GIA certificate. This is very important since you can be assured that you are buying a real diamond, and you can see the cut of the stone and a map of any inclusions.

You can be sure you are getting what Costco says you are getting. 

For diamonds under 1 ct, you will receive a certificate from Costco gemologists listing the stone’s C’s. According to Costco, all their staff gemologists are GIA trained and use the GIA system of grading. 

But even so, you aren’t going to get a GIA certificate for a stone under 1 carat, which makes it somewhat more difficult to know what you are getting, particularly with the cut.

This may account for the difference in price for stones under 1 carat.

Read also >> Are All Diamonds GIA Certified? (All You Need To Know)

Read also >> How Long Does GIA Certification Take? (Here Is What To Do)

Should I Buy an Engagement Ring at Costco?

Yes, you can get a good deal, but here are a few additional considerations:


You can browse diamonds and settings at a Costco warehouse, which means you can try on diamonds for size and shape and see what you like in person rather than online.

Costco also sells diamond jewelry online, though the images of the rings are fairly limited. 


Costco doesn’t sell loose diamonds, so if you are buying an engagement ring, you will be in for the whole ring. Online retailers will sell you just the center stone. 

If you find a setting you absolutely love at Costco, great, but there isn’t a huge selection, and you cannot customize your setting the way you can from online jewelers or Jared.

If you are planning to upgrade or switch to a different setting, you could use the Costco basic settings for the time being.

Though keep in mind that many Costco engagement rings are set in Platinum, which is expensive. If you want to save money, you may want to buy a white gold setting through an online jeweler. 


Costco rings only come in certain whole sizes, so you will need to be certain of your size (or your sweetie’s) or have a good jeweler in mind who can size the ring at additional expense. 


Maybe the biggest drawback to buying diamonds at Costco is the limited selection. You may be able to score a setting you really love at Costco–and if you can get a GIA certificate with the rock you will probably save a bunch of money on it. 

If you are buying online, you won’t get to see high-definition 3D images of your stone before purchase as you would at an online seller. 

With a small and basic selection (no designer jewelry) you may not find something you absolutely love. 


Before buying a diamond, you need to get schooled in the 4Cs. Don’t know those yet? Read up online and learn why they are important.

Costco doesn’t have jewelers in-warehouse, so you can’t ask important questions and get trusted answers. 

If you already studied up and feel comfortable buying a diamond without the help of a jeweler or diamond professional, Costco might be a good option for you.

This is especially true if you are buying over 1 ct and can get the GIA certificate.


Costco diamond rings do get high marks for customer satisfaction. Some online customers report getting a slightly larger stone than they ordered. 

If you don’t like it, you can return it for 30 days. (If it’s over 1 ct, you will have to send back the certificate and they will have to confirm with their gemologists before you get your refund.)


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 10% off select lab grown diamonds and 25% off ring settings during limited time sale!


  • 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


Most Costco diamonds are good quality, and if you know exactly what you are looking for you might be able to save money on the perfect ring.

However, not all stones at Costco have certificates–so it’s hard to guarantee the quality. 

The selection is very limited, and you can’t build your own, but that doesn’t mean you won’t find something you absolutely love. 



Lindsey graduated with an MBA in 2009. Since then, Lindsey has worked in the retail and consumer service industry as a manager, advisor, and marketer. Lindsey is also the head writer and Co-founder of Lindsey is based in Morgantown, West Virginia.

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