The best beef to buy for burger is an 80/20 ratio, meaning 80% lean beef and 20% fat. This ratio will help to prevent a dry burger after grilling and maximize juiciness. Ground chuck is most commonly used with this ratio since it is most readily available, and produces a flavorful burger. If you want to create your own blend, most butchers will grind one for you. Choose a mixture of chuck, brisket, filet, short rib, sirloin or fat cap.