One 7- to 8-ounce filet mignon will amply feed a single person, maybe with some leftovers. Because filets are often served whole, as a single-cut steak, it’s harder to adjust the serving size. Most filets mignons are 1 to 2 inches thick, and the thicker they are, the more narrow they might be in diameter. You could slice the steaks and let people serve themselves the amount they want, but the dramatic presentation of a single filet on a plate is very impressive.