Costco's August sales at stores open at least a year climbed 7 percent, which was much better than industry watchers had expected.

Comparable-store sales are a key gauge of a retailer's health because it excludes the volatility from stores that have been recently opened or closed.

Analysts polled by Thomson Reuters had been looking for an increase of only 4.8 percent.

Domestic sales led the way, rising 7 percent, compared with 6 percent internationally.

And if the impact of lower gas prices and foreign currency fluctuations are stripped away, global sales at stores open at least a year climbed 8 percent. By that measure, sales rose 8 percent overseas and 7 percent in the U.S.

Revenue for the four weeks ended Aug. 31 increased 10 percent to $8.8 billion.

For the fourth quarter, Costco Wholesale Corp. said that sales at stores open at least a year rose 6 percent. The U.S. and overseas both posted 6 percent gains.

Excluding the impact of lower gas prices and foreign currency fluctuations, sales at stores open at least a year climbed 7 percent. In the U.S. the figure rose 6 percent. It increased 8 percent abroad.

Fourth-quarter total revenue climbed 9 percent to $34.8 billion.

Full-year sales at stores open at least a year increased 4 percent. The U.S. reported a 5 percent rise. Internationally, the figure rose 3 percent.

Taking out the impact of lower gas prices and foreign currency fluctuations, sales at stores open at least a year climbed 6 percent. In the U.S. the metric rose 5 percent. Internationally, the figure increased 7 percent.

Total revenue for the year climbed 7 percent to $110.2 billion.

Costco, based in Issaquah, Washington, ended fiscal 2014 with 663 locations, including 468 in the U.S. and Puerto Rico, 88 in Canada, 33 in Mexico, 26 in the U.K., 20 in Japan, 11 in Korea, 10 in Taiwan, six in Australia and one in Spain. It plans to open up to an additional nine new warehouse stores before the calendar year ends.