How long can cooked hamburger last if not refrigerated?

According to the United States Department of Agriculture (USDA), cooked hamburgers can be left out at room temperature for up to 2 hours. After 2 hours, bacteria can start to grow rapidly and cause the hamburger to become unsafe to eat. If the temperature is above 90°F, cooked hamburgers should not be left out for more than 1 hour. Refrigerate or freeze cooked hamburgers if they will not be consumed within this time frame.