The USDA recommends that hamburger be kept in the refrigerator no longer than two days after purchasing. Hamburger should be refrigerated at 40 degrees Fahrenheit or below.
Keeping ground beef in the fridge for no more than two days minimizes the growth of harmful bacteria and preserves the freshness of the meat. If the beef will not be used within that timeframe, it can be frozen indefinitely instead. When thawing, do not leave the hamburger at room temperature for more than two hours.
To further avoid the chance of ingesting illness-causing bacteria, hamburger should be cooked to a minimum internal temperature of 160 degrees.