your guess is as good as mine
US /jʊər ɡɛs ɪz æz ɡʊd æz maɪn/
UK /jʊər ɡɛs ɪz æz ɡʊd æz maɪn/

1.
senin tahminin benimki kadar iyi, ben de bilmiyorum
used to say that you do not know the answer to a question, or do not know what is happening, for the same reason as the person asking
:
•
Why did he leave so suddenly? Your guess is as good as mine.
Neden bu kadar aniden gitti? Senin tahminin benimki kadar iyi.
•
When will the new policy be implemented? Your guess is as good as mine.
Yeni politika ne zaman uygulanacak? Senin tahminin benimki kadar iyi.