Wedding Ring Tips

Are Costco diamonds good?

​Costco has everything; you name it, they have it, and diamond rings and jewellery aren’t the exceptions here. When the word Costco comes to mind, you don’t exactly think about jewellery and diamonds, but you’re probably wondering whether they’re worth buying. So, are they any good? Keep reading to find out! 

Where do you go if you’re looking for good deals? The answer is simple: Costco! You probably go to Costco all the time and why wouldn’t you; it provides a wide array of products at incredibly affordable prices. Among many other products, Costco also sells diamonds even though you may not expect that. But, are those diamonds any good? We give you the answer.

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Background Of Costco jewellery

There is no reason for me to bother with a history of Costco — the company’s reputation precedes them. Speaking personally, I love Costco. My family and I have been long time customers of Costco, and I admire the company’s philosophies.

Costco Wholesale Corporation has built a fantastic business model of providing bulk items with razor-thin margins. For a major retail chain, their service is second to none. They also have a legendary return policy.

Costco used to have a great reputation for jewellery as well. Speaking from experience, from the perspective of a supplier, I used to be impressed with their quality control. Unfortunately, the quality of their jewellery has seemed to have slipped over the last few years.

Understanding the 4Cs

Most jewellery retailers use the Gemological Institute of America (GIA) colour, clarity, cut, and carat weight standards, also known as the 4Cs, to set the prices of stones. It’s rating for these characteristics determines the quality of a diamond. The cut is a matter of personal taste, but the quality of the cut matters to its brilliance.

Clarity is a measure of the purity of the stone, with designations like VVS1, or very, very slightly included, and VS1, for very slightly included. Colour is rated on a scale of D to Z, with D being the best, or colourless, quality. 

Costco guarantees that the diamonds it sells are at least VS2 in clarity and grade I in colour. Its diamond rings with a centre stone that is 1.00-carat or larger come with a GIA Diamond Grading Report. Diamonds over one carat come with an International Gemological Institute (IGI) appraisal that can be used to ensure the fine jewellery investment.

Shoppers who go to Tiffany & Co. (TIF) don’t have to make sense of technical reports on their own. Tiffany offers consultations during the shopping process with diamond experts in-store, by phone, or by email.

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Diamond Price Ranges

A one-carat diamond ring can sell for anywhere between $3,500 and $27,000, depending on those 4Cs, the quality of the setting, and the retailer.

As of April 2020, the Costco website lists rings starting at $249.99 for a simple stackable band set in 14k gold with a 0.08-carat VS2 diamond. The priciest offering at this writing is $364,999.99 ring set in platinum with a 7.45-carat diamond rated with VS1 clarity.

Tiffany does not use the 4Cs to describe its rings, relying on proprietary processes to handcraft jewellery set with stones. Many of the rings displayed on its website are embellished with diamonds, often clustered with other stones. A solitaire diamond ring starts at about $13,000, with many customizable options for size, colour, and setting.

Online diamond retailer Blue Nile Inc. (NASDAQ: NILE) sells loose diamonds as well as preset diamond rings and lists one-carat stones starting at about $2,400. Blue Nile shoppers can choose from several setting styles for the diamond that they select at an additional cost. It uses the GIA rating system.

Customization and Service

Old-fashioned jewellery stores allow customers to customize their purchases. If you like a stone in one ring but the setting of another, many jewellers will make a custom version for you. Some even allow you to design your own ring and will work with you to produce a one-of-a-kind ring based on your description.

When you purchase a ring from a traditional jeweller, you also can generally take it back when it needs cleaning or repairs, or even to have a gemstone reset in a new piece of jewellery.

All Costco diamond rings are pre-made, and buyers don’t have the option to customize them. The specifications on the Costco website list ring sizes, but you will have to take your ring to a jeweller if you need to have it sized to fit.

Costco does not offer cleaning or repairs for its jewellery.

Looking for wedding rings check out our list Wedding Ring Shops in Melbourne.

Overall experience

While Costco is a perfect place to buy just about anything and still leave the place with money in your wallet, it’s not that good as a jewellery retailer store. The first problem we came across is that staff didn’t have the necessary knowledge about diamonds. After all, if you’re in charge of something (in this case diamonds) you should make an effort and learn a thing or two. At Costco, buying diamonds is like choosing fresh produce, but at the end of the day, diamonds aren’t groceries, and you do need to consider some factors before buying them. In order to inspect the quality and see how they compare to some other diamonds on the market we purchased 0.70ct I VS2 round diamond in a solitaire setting. It is easily noticeable that the diamond lacks essential cut material.

Also, we wanted to test their 1.13ct G colour VVS2 diamond and compare it to those at the Blue Nile, more precisely their 1.13ct G colour VVS2 clarity round ideal cut blue diamond.

Limited selection

The biggest problem with Costco diamond store is lack of selection. Only a few options are available, and that’s it. On the other hand, craftsmanship and quality of diamonds are decent. It would be nice to see more options for people who prefer different styles.

Not all is negative about Costco’s diamonds and engagement rings. Probably the best feature of their jewellery store is an amazing return policy. You’ll be surprised to know that Costco has one of the most liberal and generous return policies in the industry. It’s incredibly easy to return a product without too much hassle, which is always a good thing.

The Value

While you probably assume rings and diamonds from Costco, are garbage, it’s important to clarify they have a great quality. Unfortunately, good quality doesn’t automatically indicate better value. For instance, the 0.70ct diamond cost about $3503.99 with tax. What’s wrong about this? It means the price tag doesn’t do the justice to quality. In order to conclude a diamond has the value, the price has to match the quality, and in this case, it doesn’t.

At James Allen’s store, one can find an almost identical diamond for a 25% lower price and pay $2610 only.

Buy online at Costco also, the 1.13ct ring from Costco cost $24,800, but Blue Nile’s ring outperforms it because the offset for crown and pavilion angle is more conducive to light return. While both diamonds are GIA-certified, only proportions of Blue Nile’s version are within the range specified by the AGS Laboratory. Let’s not forget to mention that Blue Nile’s ring cost $11.301, way cheaper than at Costco.

Also, when buying jewellery from Costco, you have to pay state sale tax while online-only stores allow you to navigate your way around this problem and save money.

Check out our post on What jewellery should a bride wear?

The Costco Engagement Ring Shopping Experience

Costco is a phenomenal retailer, but they are a terrible jewellery store. There are no knowledgeable staff members and no value-added services. You pick out the diamond the same way you pick out a shampoo bottle or one of their delicious cheesecakes. I went with a 0.70ct I VS2 round in a solitaire setting.

We always recommend that our readers contact us for specific advice when buying a diamond from a local jeweller. If you were to contact us after looking at a diamond ring at Costco, you would invariably get better, more thorough advice from us and whichever online retailer we recommend. That should be the one area a brick and mortar retailer should excel in, not fall behind.

This is where you start to see cracks in the Costco experience. Not only was the diamond lacking a GIA certificate, but it also didn’t have any certificate at all.

To their credit, this was a well-cut diamond (I can’t give specifics as it was mounted already) and the clarity grade was fair. However, the diamond was a J colour, not the I colour they claimed it to be. Learn more about cut, colour, and clarity in our useful guide on the 4cs.

The actual setting, while simple, was fantastic. It was a classic four-pronged platinum solitaire. The craftsmanship and quality were on par with any company that I would entrust. Overall, the ring I purchased was a nice choice, right in line with our recommendations (an eye-clean, well-cut J colour for a solitaire).

Costco Ring Setting And Style Selection

Another issue that crops up is their lack of selection. At any given store, they will only have 10-20 options. The quality and craftsmanship are fantastic, but that leaves little room for individuality and personal tastes. Even if you look online, their options are limited. They only have about seven different solitaire setting options for round diamonds. To contrast, James Allen has about 50 settings covering a vast array of ring styles, and the Blue Nile has an eye-popping 66 different solitaire selections. The ring we bought was a perfect example. While it was very nice, my friend (who joined me for the secret shopping and tried on the rings) was not overwhelmed by the style. Afterwards, we were looking online, and she was immediately drawn to a more delicate style like this 1.5mm comfort-fit setting.

Costco Diamond Price And Value Comparison

Though the ring is nice, the value is just not there. The ring cost $3,503.99, including tax. Any way you cut it, the price is not justified by the product. Two comparisons can be made here, one based on my grading (J VS2) and one based on their grading (I VS2).

Here we have a beautiful 0.70ct J VS1 to go along with this platinum solitaire setting from James Allen. This is a virtually identical ring, retailing for $2,740, a whopping 25% cheaper with sales tax included. Please don’t take our comparisons here as recommendations for what you should buy (though that is a great looking diamond). We are just trying to find similar diamonds, so we compare apples to apples. If you are looking for help buying an engagement, contact us, and we will make personal recommendations for you.

Even if you want to go with their grading (despite them no longer using GIA certification), you would still save 28% if you went with this 0.70ct I colour VS2 Clarity Excellent cut from the Blue Nile and paired it with this solitaire setting.

Those savings, while significant, are not as dramatic when comparing other brick and mortar retailers to online retailers. Given Costco’s lack of diamond service, however, I think that drop is very significant.

You don’t have service for sizing, any sort of warranty, and there is a very limited selection of setting/diamond options. While you can do some research and due diligence on your own, there is no personal service at Costco.


The quality of the diamonds Costco sell is questionable, considering most of them come with no accreditation whatsoever. You would expect them to at least have been certified by IGI, but all you get when you purchase a diamond ring under a certain carat from Costco is their own appraisal for insurance purposes.

It is widely recommended that you have the stone appraised by an expert as several reviewers have reported that they did not receive the quality of stone they ordered. In my humble opinion, if a diamond does not come with any kind of certification steer clear. Especially when you consider the comparisons above which indicate you are paying well over the odds for un-certified stones.

We struggled to discover what the criteria were on which the accreditation you received was based. Buried in the FAQ section, it states that it depends on the carat, or size, of the diamond. More than 1.25ct comes with a diamond grading report from AGS and an appraisal certificate from IGI.

Their one of kind pieces come with both regardless of a carat. IGI is not one of the better gem labs and does not have the same high standards as GIA; for example, these certificates are not worth as much. However, they are still better than the stone just being inspected by an in-house graduate gemologist as is the case with the smaller stones.

Sorry, but this just isn’t good enough. Go to a retailer such as Whiteflash or James Allen and even their smallest stones come with certificates from AGS or GIA. As even a stone of 0.9ct carries a price tag of several thousand dollars, you are entitled to know the true quality of the stone you are buying.

The Choice

The choice isn’t as vast with their jewellery being a department as opposed to a dedicated site. Nevertheless, there is a decent selection of engagement rings available. There are 56 engagement rings in total to choose from in the engagement ring section and a further 77 in the engagement rings collections section.

You also have the option of choosing your own stone, but the setting is selected for you. This doesn’t sit well with me either as the setting is extremely important, and here there is no choice of metal, you get what you are given.

It is little, or no choice of sizes available with Costco rings either. Every ring comes in size 7, and a few have one or two sizes either side of this. It states that the rings can be re-sized by one size either way, but Costco does not deliver this service.

Anyone with an idea of the preset ring they are looking for, are shopping for someone with a size 6,7 or 8 fingers and want a super quick shopping experience will probably welcome this reduced choice. However, as we showed above, shop around before you buy as chances are you will find cheaper elsewhere.

The Packaging

There is nothing at all on the site about the ring packaging, so another trip to Google was required. There was absolutely no info there either. I am sorry that I can give you no information on this whatsoever.

The box you get your ring in is so important when it comes to that big, down on one knee moment. All I can recommend if you decide to shop from Costco is to go to a store and ask to see their boxes or make a mental note to track down a good box depending on what arrives.

The Returns Policy

It takes a bit of time to track down the returns policy for their jewellery as they have several depending on whether you have purchased a ring or a washing machine. However, we discovered a returns/warranty section underneath each piece.

This looks pretty straightforward, but there is no mention at all of how long you have to return your item. Although the standard is 30 days, we recommend you find out for definite by calling a store.

You won’t be disappointed with the quality of your purchase. However, Costco is nowhere near close to offering the best price for quality diamonds.

If you are buying an engagement ring or stud earrings, you can get far better value and service using a legitimate online retailer. Additionally, you should never buy a diamond without a legitimate certificate (like GIA or AGS).

While we love Costco, their jewellery store needs more improvements. Staff lacks basic knowledge about items they are in charge of, a limited selection of diamonds, and no certifications are just some of many problems. While quality and craftsmanship are decent, to provide quality service, it is essential to take care of other factors as well. Although you won’t be disappointed with the quality of purchase, Costco is not the best place to purchase to save some money, which is kind of ironic since they can help you save up with everything else. For comparison purposes, we recommend you look into this online retailer instead. They are the recipients of our prestigious 5 Diamond Award. 

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