Analysts polled by Thomson Reuters predicted a 4.5 percent increase.
This figure is a key gauge of a retailer's health because it excludes results from stores recently opened or closed.
Costco Wholesale Corp. said Thursday that U.S. stores reported a 4 percent rise in the metric, while those abroad posted a 3 percent gain.
Total revenue for the four weeks ended May 5 rose 7 percent to $7.98 billion.
For the year to date, revenue at stores open at least a year rose 6 percent for the total company as well as for U.S. and overseas locations.
Excluding the impact of gasoline prices and foreign currency exchange rates, the wholesale club operator's April revenue at stores open at least a year increased 6 percent. The U.S. and stores abroad also reported 6 percent gains for the month. A 6 percent increase in the metric was also reported for the year-to-date for the total company, U.S. and international locations.
Costco plans to report its third-quarter financial results on May 30. The Issaquah company runs 627 warehouses, including 449 in the U.S. and Puerto Rico, 85 in Canada, 33 in Mexico, 24 in the U.K., 15 in Japan, nine in Taiwan, nine in Korea and three in Australia. It plans to open nine additional new warehouses before its fiscal years ends on Sept. 1.