Walmart beating Costco in trillion-dollar race (but it's close)

If you were asked to identify some of the fiercest, most competitive industries in the U.S., a couple might spring to mind. 

By the numbers, some of the largest industries in the country are: 

• Real estate
• Manufacturing
• Health care
• Finance and insurance

Related: Major drugstore chain closing hundreds of struggling stores

But many of these industries are either fractured and localized, or completely dominated by a few central players. 

That's not to say competition isn't fierce in any of the above sectors. It certainly is, and it's part of what keeps prices competitive for consumers and makes our nearly $30 trillion GDP the largest in the world.

But if you zoom into a more localized level, the average American isn't talking about competitive edges between manufacturing giants or the clash of insurance titans. 

Take a drive through an average American town, and you'll see that the typical person is more concerned about filling up their car with reasonably priced gasoline or putting food on the table. 

And, if you'd ask them what corporate competition is relevant to them, they'd probably tell you it has to do with groceries. 

Groceries are big business

It's estimated that the U.S. grocery industry will be worth $1.6 trillion by 2025. 

While that's certainly a big number, the inner workings of the grocery industry are complicated and splintered.

Grocery is notoriously one of the most difficult markets to make a mint in. 

More Walmart:

• Walmart, Kohl's raise alarm bells about a growing threat
• Sam's Club making big new Costco-style membership change
• Walmart's Sam's Club drops self-checkout, adds new anti-theft tech
• Sam’s Club making major change to rival Costco

That's because supermarkets run with notoriously low profit margins. The average store only brings in between 1-3%, even during the best of times. 

This means that a grocery store must sell a lot of inventory to make any meaningful profit. And all that inventory is perishable, so it must get moved and restocked quickly.

Plus, customers are increasingly price-sensitive and decreasingly brand-loyal. This means if a store suddenly raises prices, customers will notice and go elsewhere for their goods.

Add to this all the typical costs associated with running large warehouse-style retailers — high rents, high utilities (consider how much it costs to run all those refrigerators, often with open displays), and a high cost of labor. 

So $1.6 trillion may sound like a lot of money. To be sure, it is. But it goes pretty quickly in such a competitive, resource-intensive market.

Walmart, Costco in heated contest

Still, the grocery industry is steadily growing. 

And along with it, so are a few national giants.

A new report by Numerator lists the largest grocery stores in America, and the number one grocer since 2019 is Walmart  (WMT) . 

In fact, the retailer is so large that you would have to add together the next four largest grocers — Kroger, Albertsons, Publix, and Ahold Delhaize — to rival Walmart's size. 

Walmart accounted for about over 20% of all dollars spent on groceries in the U.S. during the quarter ended March 31, 2025. This means about every one in five dollars spent on groceries is spent at Walmart. 

Related: Amazon customers get bad news for upcoming Prime Day

Here's the list of top grocers in America, per the new findings: 

1. Walmart: 21.2%
2. Kroger: 8.9%
3. Costco: 8.5%
4. Albertsons & Co: 5%
5. Publix: 4.1%

Notably, Walmart-owned Sam's Club is number six, at 4%. This means Walmart-owned companies account for over one quarter of groceries stores in America, a massive achievement. 

But Costco is accelerating its growth, rapidly gaining market share. 

In 2023, Costco's market share was at just 7.6%. Two years on, it's gained almost two full percentage points, indicating shoppers are seeking value and shopping around for best prices — and other unique membership benefits.