your guess is as good as mine
idiom
Meaning
An expression used to admit that one has no more knowledge or insight about a situation than the person asking.
Examples
- I have no idea why the server crashed; your guess is as good as mine.
- When asked if the project would be finished by Friday, the manager shrugged and said, 'Your guess is as good as mine.'
Synonyms: I don't know, I have no clue, who knows, it's anyone's guess