The data: Costco is gaining share at the expense of traditional grocers like Kroger and Albertsons, as well as mass merchants like Walmart.

• The retailer’s customer base expanded by 4.5 million households in the 12 months ended August 30, according to Numerator data reported by Chain Store Age.
• Costco gained $2.5 billion in CPG spending, including more than $1 billion redirected from Walmart, Kroger, and Albertsons and another $570 million from independent grocery, gas, and convenience retailers.

Behind the numbers: Rising gas prices have helped increase the value of a Costco membership as consumers look for relief at the pump. Management noted that the retailer’s gas business had a record year in fiscal 2026 (ended August 30), with the share of US member households purchasing fuel reaching an all-time high.

Traffic to Costco is growing faster than at competitors, with overall visits rising 8.2% YoY between April and July, compared with 4.9% growth at BJ’s Wholesale Club, a 4.7% increase at Sam’s Club, and just a 0.7% rise at Walmart, per Placer.ai.

At the same time, shoppers are turning to Costco for more than just lower-priced gas. The retailer pointed to strong sales in a number of categories, including both consumables and discretionary products, as well as rising demand for “ancillary” services like pharmacy and travel. Ecommerce sales are also growing at a healthy clip, helped by higher traffic to Costco’s website and app as well as personalization initiatives that are delivering more relevant recommendations to members.

Implications for retail: Fuel discounts are proving to be a key traffic and loyalty driver—albeit one that more companies, from Amazon to McDonald’s, are using. Amazon recently announced extra gas savings every Friday from October 2 to January 29 for Prime members, while McDonald’s temporarily partnered with Shell on fuel discounts for loyalty members.

However, these more limited measures are unlikely to diminish Costco’s edge. The retailer’s ability to offer significantly cheaper gas than its competitors, coupled with the price advantages of bulk-buying, will serve as a reliable traffic and sales driver as economic uncertainty lingers.

Go further: For more on Costco’s performance, check out our Live Earnings Report: Retail & Ecommerce Tracker Q2 2026.