Costco’s September Sales Jumped 13%: Why an 8% U.S. Adjusted Comp Tells a Better Story Than the Headline

Consumer spending looks different when the retailer offers value

Costco Wholesale's new monthly sales figures provide a useful counterpoint to the concerns about household inflation and weak branded-food volumes. The company reported $30.02 billion in net sales for the five-week retail month ended October 4, 2026, an increase of 13.0% from $26.58 billion a year earlier. The company issued the release on October 7, making the numbers fresh information for the October 8 U.S. trading session.

The result may appear to say that U.S. consumers are spending enthusiastically despite higher fuel bills and tight financial conditions. But a better reading separates sales growth, comparable-store performance, calendar effects and business mix. Costco can gain share from other retailers precisely because households are becoming more price-sensitive. Rising sales at a discount-oriented membership retailer therefore do not necessarily imply an equally strong consumer environment everywhere.

What the five-week sales statement showed

Reported comparable sales rose 11.4% across the company, including 12.5% in the United States, 6.3% in Canada and 10.8% in other international markets. Those are reported comps, not constant-currency, gasoline-adjusted comps. Removing the effect of changes in gasoline prices and foreign exchange, companywide comps rose 7.6%, including 8.0% in the United States, 4.9% in Canada and 7.7% internationally.

Digitally enabled sales grew 19.0% as reported, or 19.1% excluding currency effects. Costco defines those transactions broadly as sales initiated through a digital device, whether fulfilled in a warehouse, a distribution center or through Costco Travel. That definition is wider than the most restrictive interpretation of parcels shipped by an online store, so it should not be equated automatically with pure e-commerce delivery revenue.

The company said the later timing of Labor Day in the United States and Canada contributed a little more than 50 basis points to September reported total and comparable sales. That means part of the month-on-month narrative reflects where a holiday fell on the calendar rather than a permanent shift in shopper behavior. The company operated 939 warehouses at the time of the release, including 647 in the United States and Puerto Rico.

Why the adjusted number is the better demand signal

The gap between U.S. reported comps of 12.5% and adjusted comps of 8.0% is meaningful. When fuel prices jump, the nominal value of gasoline sales can increase even if the number of gallons sold does not rise at the same pace. Foreign exchange can similarly change international reported sales without altering local-currency demand. By showing both measures, Costco gives investors a way to separate some price and currency effects from underlying customer spending.

Even the adjusted 8.0% number is not a perfect volume measure. Comparable sales still reflect transaction frequency, basket size, product mix and selling prices. A larger basket can indicate customers consolidating trips or shifting more spending into Costco; it can also partly reflect inflation in necessities. For margin analysis, the proportion of gasoline, pharmacy, food, discretionary products and ancillary services matters.

Costco's model encourages regular visits through membership economics, perceived value and bulk packs. In a high-inflation environment, that can help the retailer capture wallet share even as household purchasing power is pressured. The retail story is therefore partly defensive and partly competitive: Costco may be doing well because its customers are affluent enough to keep spending, because it offers better prices, or because consumers are transferring purchases away from rivals. Those explanations have different implications for the rest of the sector.

Why digitally enabled growth deserves scrutiny

Nineteen percent digital growth is strong, but the denominator and fulfillment method matter. Digitally initiated grocery pickups, travel bookings and shipped orders can generate different gross margins, labor requirements and repeat behavior. Investors should look for evidence that digital growth increases member convenience and frequency without diluting profitability.

There is potential strategic value. Members who use Costco through more channels may renew more consistently and spend across a wider range of categories. But digital activity may also involve lower-margin promotions or service costs. Faster revenue growth alone cannot resolve that trade-off.

The company has recently highlighted the value of its gasoline business and strong renewal economics. Cheap fuel can attract visits, yet volatile fuel prices can distort reported sales comparisons. In an environment of Brent above $104, that distinction becomes especially important for interpreting the September data and evaluating subsequent months.

The market debate: durable market-share gain or calendar-aided strength?

The bullish case is that 7.6% adjusted companywide comps and 8.0% adjusted U.S. comps point to a business with considerable momentum. Strength across physical warehouses and digitally initiated sales may indicate a model that is gaining relevance as consumers seek value. Membership fees can help fund pricing competitiveness and support the overall economics of the retail operation.

A more cautious view asks how much of growth stems from price inflation, holiday timing, category mix or temporary promotional activity. The 50-plus-basis-point calendar benefit is explicitly acknowledged by management, and gasoline-related effects also matter. A retailer with strong sales can still disappoint earnings expectations if wages, freight or product costs rise faster than it can preserve merchandise margins.

Competition is not static. Walmart, Target, Amazon and regional grocers can adapt their pricing, delivery and membership offerings. Costco must keep product quality and availability high while opening warehouses and maintaining a compelling member proposition. A premium valuation can also make the stock vulnerable if adjusted comps slow even modestly from a strong base.

What to watch next

The company said its prerecorded discussion of the September report would remain available through October 14 at 4:00 p.m. Pacific Time. That is a confirmed information-access date, not a new earnings or sales release. Costco had not confirmed a separate next monthly-sales publication date in the materials verified at this cutoff, so one should not be invented.

The next useful metrics are adjusted U.S. comps, total shopping frequency, digital fulfillment economics, gasoline effects and membership trends. For investors comparing Costco with branded packaged-food companies, the most revealing question is whether the retailer continues gaining share while manufacturers struggle to defend price and margin. That comparison is a test of consumer choices, not evidence that any one company's sales caused another company's weakness.

Conclusion

Costco's October 7 release supplied a credible positive consumer signal entering the October 8 session: September sales rose 13% to $30.02 billion, with adjusted U.S. comparable sales up 8% and digitally enabled sales up 19%. The evidence supports strong execution, but not an unqualified claim that household demand is booming. Fuel, currency, calendar and mix all shape the reported figures. The investment question is whether Costco can sustain traffic and membership value while preserving margins as inflation and competition continue to pressure the broader retail market.