Updated November 29, 2022

Costco Diamond Review: Is It Good?

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When it comes to value, a Costco diamond ring is hard to beat. But there are drawbacks to be aware of. Read on to find out if Costco diamonds are any good.

5-point scale (the higher, the better)

Pros and Cons

  • Generous return policy
  • Good pricing
  • No customization
  • No resizing or warranty
  • No customer service

Bottom Line

Offers great value on diamond rings, but also plenty of downsides

Costco sells engagement rings at good prices. But are the diamonds themselves any good?

And should you really be buying a ring at the same place you buy bulk toilet paper?

Here are 8 things to know before buying an engagement ring from Costco. Plus, see how Costco's prices compare to Zales, James Allen, Blue Nile, and other retailers.

Bottom line: Costco can be a good choice if you're looking for low pricing plus in-person shopping. Overall, Costco diamonds are of decent quality and offer great value, as long as they're GIA certified. You can find a ring for 50% less than at other big-name jewelry stores.

But compared to online retailers, Costco cannot match their selections, customization, or service.

Costco Diamonds Pros & Cons

Want a quick takeaway before diving into the details? Here are the must-know pros and cons of engagement ring shopping at Costco.


  • Good value - a lot cheaper than other big-name jewelers
  • You can see and try on the ring in person
  • Diamonds are pre-screened for quality
  • Hassle-free returns


  • No customization at all
  • Small limited selection
  • Not all diamonds are GIA-certified
  • No jewelry specialists to answer questions
  • No ring resizing or after-purchase service

What's the best place to buy an affordable ring?
Your best bet to get a quality, budget-friendly ring is to try an online jeweler. Sites like Brilliant Earth only sell certified diamonds. Plus, you can customize the ring to get the best cut, color, clarity, and carat.

Now, let's get into the detailed review.

What to know before buying diamonds at Costco

Gearing up to buy an engagement ring? Before you head into the local Costco to score a deal, here are 8 important factors to consider. Are Costco diamonds really as good a value as they say?

1. Costco Diamond Quality Can Vary

Costco guarantees that all their diamonds are at least a VS2 clarity and I color, or better. In our research, the majority of their diamonds fall into these grades.

This is considered a pretty decent diamond. At VS2 clarity, it's a safe bet that the diamond is eye-clean. I color is in the near-colorless range, but the diamond will still appear white.

These grades give you a good-value diamond, where the price is lower but the stone still appears flawless to the naked eye.

Some other high-end jewelers, like Tiffany, also have similar minimum quality standards for their diamonds.

The problem, though, is the cut grading. Diamond cut is the most important factor. It's what makes the diamond sparkle and shine. Costco does not provide a cut grade for all their diamonds, so that makes it hard for us to say if those diamonds are good quality.

And if you're looking for premium, super high-quality diamonds, don't expect to find them at Costco.

2. Not All Diamonds are Certified

Costco claims to use the GIA grading standard. GIA (Gemological Institute of America) is the world's leading lab because of its high standards and consistency.

Costco says that they have a team of GIA graduate gemologists. They inspect every diamond to make sure that it meets Costco's quality standards.

Costco provides these reports:[1]

  • For diamonds less than 1 carat: You get a Costco Article of Description that states the diamond details. Based on our research, these diamonds don't have a cut grade.

  • For diamonds 1 carat and larger: You will get a GIA diamond grading report, as well as a gemological/jewelry report from Costco. Sometimes, the diamond also has an IGI certificate (which is another grading lab).

It's not great that Costco diamonds less than 1 carat aren't certified by GIA. Without an official GIA (or another lab) report, you'll have to trust Costco's own in-house grading. That's not proper proof of quality. And we don't know how accurate Costco's grading is.

It costs more money to get diamonds certified by GIA. Since Costco uses their own certification for smaller stones, that's probably why they're able to offer them at lower prices.

Why certification matters: A proper lab certificate authenticates the diamond's quality. Without a certificate, the seller can just write whatever quality they want to make their diamonds look better. You could be paying for a VS2, I diamond, when in reality, the quality is lower.

We're not saying Costco does this, but you don't know the true quality without a grading report from a reputable lab.

3. All Rings are Pre-Set

All Costco's engagement rings are already premade. There are no options for customization at all.

This makes it hard to find the perfect ring. You could love a certain ring design, but the diamond isn't the size or shape you want. Or maybe you prefer a rose gold metal instead. Or the ring itself isn't your finger size.

Basically, for Costco to be worth it, you must find a ring in your perfect size, shape, and setting, and within your budget.

But this is extremely difficult when there are so few choices. This brings us to the next point.

Can you return diamonds to Costco? Yes, you can return diamond engagement rings to Costco for a full refund including all shipping and handling charges. If you bought a diamond of 1 carat or larger, you must bring the original GIA or IGI certification.

4. Choices are Limited

Costco has a tiny selection of engagement rings. Currently, on the Costco website, there are just over 300 engagement rings available. Your local Costco warehouse may or may not have better selections.

You can also see the breakdown of the price ranges and metals. For example, if you want a rose gold ring, there is literally only 1 choice. Most of the options are platinum.

On the other hand, online diamond retailers like Brilliant Earth let you design your engagement ring. You can custom-make your own perfect ring in just minutes—without a high markup.

5. No After-Purchase Protection

Costco does not offer resizing or a warranty after you have purchased the engagement ring. This is a pretty big downside.

What if you get the wrong size? What if a small diamond falls out because of a manufacturing defect? You'll have to find your own jeweler to fix the issue.

Reputable diamond jewelers all offer after-purchase protections. They'll usually offer a complimentary resizing (even up to a year after purchase) and lifetime warranty. Some jewelers will even cover cleaning and maintenance.

If you're shopping with your partner and know for sure that the ring fits, then maybe no resizing isn't such a big deal. And if the savings are truly significant, then you can service the ring yourself at a local jeweler.

Platinum rings will need regular polishing to keep it shiny. White gold rings will need rhodium re-plating every couple of years to maintain the color.

6. Generous Return Policy

This is one of Costco's strong points. Costco is known for its generous return policy, which also applies to jewelry.

If you don't like the ring, you can return it at any Costco warehouse for any reason, no questions asked.

For diamonds 1 carat and larger, you must also return with the original GIA and/or IGI certification. You'll first receive a Jewelry Credit Memo. After Costco's gemologist inspects the diamond (and confirms that it's the same one that was sold), you'll get your refund. This may take up to 5 business days.[2]

7. You Will Not Receive Expert Help

The staff at Costco are not specialized jewelry experts. Don't expect them to be able to offer professional advice. It's pretty much an on-your-own shopping experience.

In comparison, your local independent jeweler can sit down with you and help you compare options and teach you about diamonds.

Even online diamond retailers offer better support. James Allen lets you chat and screen-share with a gemologist if you need help picking a diamond. Blue Nile and Brilliant Earth both offer private virtual appointments with jewelers to talk about anything you want.

Are Costco diamonds conflict-free? "Costco Wholesale shares the concern of the global community in abolishing conflict diamonds, and is committed to procuring goods of the utmost integrity. We are proud to sell beautiful, high-quality diamonds that are obtained solely through closely monitored legal channels set forth by the United Nations' Kimberley Process."[3]

8. Be Careful of Carat Weight

Costco does this tricky thing in the diamond ring description. They'll write the total carat weight instead of the carat weight of the center stone.

For example, this oval ring above has a 1.13 ctw. This means that the carat total weight is 1.13 carat. The center stone is just 0.50 carat. That and all the other little diamonds added together equal to 1.13 carat.

This isn't too big of a deal. But it's important to understand this distinction, or else you may be disappointed when the diamond is smaller than expected.

Costco Price Comparison Against Other Retailers

Are Costco diamond rings really a good value?

Below, compare engagement rings from Costco against popular online retailers James Allen, Blue Nile, and Brilliant Earth. These companies have excellent reputations with competitive pricing.

We also included a comparison to popular jewelry retailer, Zales.

How much are you spending on a ring?

Costco vs James Allen (Classic Solitaire Ring)

First up: This 1 carat solitaire platinum ring on Costco for $5,899.99. The diamond is graded I color, VS2 clarity, and Very Good cut by GIA.

Below, a similar ring from James Allen with a platinum solitaire setting for $1,300. This 1-carat diamond from James Allen costs $4,710. We even upgraded it to an Excellent cut, so it's better quality. In total, creating the same ring on James Allen would cost $6,010.

For only about $100 more, James Allen is the better choice because the diamond has a higher cut grade. James Allen also has other solitaire settings for less, so you can even reduce the price (we picked the one that was most similar).

In comparison, a similar 1-carat diamond solitaire platinum ring costs $12,999 at Zales - over twice the price. And it's unclear if Zales diamonds are certified by a proper lab.

We don't recommend getting Very Good cut grade. Cut is what makes the diamond sparkle, so we always suggest getting an Ideal/Excellent cut. For this reason, we wouldn't recommend this particular ring from Costco.

Costco vs James Allen (Round Halo Platinum Ring)

This halo pavé ring has a 1-carat round diamond with an oval-shaped halo. The center diamond itself is I color, VVS2 clarity, and Excellent cut.

Below, a similar setting from James Allen for $2,290 (in platinum). We added this 1-carat round diamond with the same specs for $5,210. In total, this ring on James Allen will cost $7,500.

This cost is comparable. The total carat weight for the James Allen ring is actually 1.50 carat - a little more than Costco's. So the extra few hundred bucks makes sense.

Because this Costco diamond is GIA certified and has an Excellent cut, we'd say it's a great ring at a great price.

Most of Costco's premade rings are set in platinum. While platinum is a good, durable metal choice, this doesn't give you the option to save more money by choosing a white gold ring instead.

On James Allen, the same setting in white gold is $1,520. That would make the total cost of the ring $6,730. It's a great way to save since white gold has the same look as platinum.

Costco vs Blue Nile (Three-Stone Ring)

This classic three-stone ring from Costco has a 0.60 carat round diamond center, plus two 0.30 carat diamonds on either side - adding up to 1.2 carat total. The price is $3,000.

We designed a similar ring on Blue Nile by picking our own diamonds. The total cost on Blue Nile came out to $3,768 (with a discount on the setting). Costco's ring does cost a lot less.

However, we chose high-quality ideal-cut diamonds to make sure they'll sparkle. And Blue Nile diamonds are all GIA certified, whereas Costco doesn't have a cut grade or certification for these smaller-sized diamonds.

These details are important enough to be worth the extra cost. But this is a personal decision based on what you value.

In comparison, a similar ring on Zales costs $6,099. And plus, it's smaller just 1 total carat weight.

Costco vs Brilliant Earth (Platinum Halo Ring)

Finally, let's look at this split-shank halo ring from Costco for $5,000. It has a 0.90 carat center diamond, with a total carat weight of 1.35 carat.

We found a similar split shank halo setting ($2,990 in platinum) on Brilliant Earth. We added an ideal-cut 0.90 carat diamond for $3,220. The total cost is $6,210.

This is a big price difference. But since Costco's diamond is less than 1 carat, there is no official certification or cut grade. Brilliant Earth's diamond is certified by GIA and is Ideal cut, which is more desirable.

We couldn't find an exact match on Zales, but this ring is similar with an oval diamond. It has a slightly smaller total carat weight and the diamond quality is lower. Plus, it's white gold instead of platinum. The cost is a staggering $11,999.

Verdict: How Costco Pricing Compares

Compared to traditional brick-and-mortar diamond retailers, then yes, Costco offers amazing value. The prices can be just half the cost of a similar ring at a big-box jewelry store.

Compared to online jewelers, here's the general observation:

  • Diamonds 1 carat and above have similar pricing, since the diamonds are certified by GIA.
  • Diamonds under 1 carat are cheaper at Costco, since they're not certified.

Unfortunately, we can't really recommend purchasing an uncertified diamond, even though you can save a ton. This will need to be a personal choice.

If it were a choice between shopping at Costco or an online retailer, we can much more readily recommend the latter. You can create a custom ring from a huge selection. The diamonds are all certified, and you'll have peace of mind with free resizing and a lifetime warranty.

Conclusion: Should You Buy a Costco Engagement Ring?

We do agree that you can find an amazing deal at Costco. But the downsides make it hard to give a wholehearted recommendation.

Purchasing a diamond ring from Costco could be a good idea if:

  • You happen to see a ring you LOVE that fits your budget.
  • You know for sure that the ring fits.
  • You've compared prices against other retailers.
  • You've done your own diamond research and education.
  • The diamond is 1 carat or larger and has a GIA certification.
  • You have a local jeweler you can go to for resizing, maintenance, or repairs.

Yes, this is a pretty long list of stipulations. We're not saying Costco is bad. Our goal is simply to tell you the facts so you can make an informed decision.

The small selection, no certification for many diamonds, and no after-purchase service are all big downsides. You'll have to decide for yourself if you're comfortable with it.


  1. ^ Costco Wholesale Corporation. What documents will I receive with my Costco.com jewelry order?, Retrieved 11/28/2022
  2. ^ Costco Wholesale Corporation. Can I return jewelry purchased on Costco.com?, Retrieved 11/28/2022
  3. ^ "FAQs Costco Jewelry": Costco, 2021.
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Anna G is a contributing writer at CreditDonkey, a diamond jeweler comparison and reviews website. Write to Anna G at feedback@creditdonkey.com. Follow us on Twitter and Facebook for our latest posts.

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44% $1,000 to $5,000
20% $5,000 to $10,000
10% More than $10,000
Source: CreditDonkey
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