it beats me

(it) beats me

slang A response when one does not know the answer to a question. A: "How long has this milk been in the fridge?" B: "Beats me. Check the expiration date." When's Ali's birthday? Beats me! It beats me—I have no idea how to get to the mall from here.
See also: beat

it ˌbeats ˈme (why, how, etc.)

(informal) I cannot understand (why, how, etc.): It beats me how he can afford a new car on his salary.What she does with her time beats me.
See also: beat