Fig. to fail to hit something by a great distance; to land wide of the mark. Ann shot the arrow and missed the target by a mile."Good grief, you missed by a mile," shouted Sally.
Fall short, fail by a considerable amount, as in Your guess as to the winner missed by a mile. This expression employs miss in the sense of "fail to hit something aimed at," a usage dating from the late 1400s, and by a mile for a great distance or interval, so used since Shakespeare's day.